ISO 18115-1:2023 Demystified: The Essential Guide to Surface Spectroscopy Terminology for Biomedical Researchers

Abstract

This article provides a comprehensive guide to ISO 18115-1:2023, the international standard for vocabulary in surface chemical analysis. Tailored for researchers, scientists, and drug development professionals, it explores the foundational terms, methodological applications, and practical implementation of standardized terminology in techniques like XPS and AES. The content covers the recent updates to the standard, offers strategies for avoiding common pitfalls in terminology usage, and highlights the critical role of a unified vocabulary in ensuring data comparability and reproducibility in biomedical and clinical research.

Understanding ISO 18115-1:2023: Building Your Core Vocabulary for Surface Analysis

What is ISO 18115-1? Scope and Structure of the International Standard

ISO 18115-1:2023 is an International Standard titled "Surface chemical analysis — Vocabulary — Part 1: General terms and terms used in spectroscopy." Maintained by Technical Committee ISO/TC 201/SC 1, this document provides standardized definitions for terminology used in the field of surface chemical analysis [1]. The standard establishes a common language that enables clear communication among researchers, scientists, and technicians working with surface analysis techniques across various sectors, including materials science, pharmaceuticals, and nanotechnology.

The vocabulary document has evolved through several editions to address the rapidly advancing field of surface analysis. The 2023 edition represents the third and most current version, superseding previous versions including ISO 18115-1:2013 and ISO 18115-1:2010, the latter of which has been officially withdrawn [2]. This ongoing revision process ensures the vocabulary remains relevant to contemporary analytical needs and technological developments.

Scope and Coverage

The scope of ISO 18115-1 is specifically focused on defining general terms and those used in spectroscopy-based methods for surface chemical analysis [1]. It forms part of a multi-part vocabulary standard, with other parts dedicated to different methodological families:

• ISO 18115-1: Covers general terms and terms used in spectroscopy [1]
• ISO 18115-2: Covers terms used in scanning-probe microscopy [3]
• ISO 18115-3: Covers terms used in optical interface analysis [1]

This structured approach ensures comprehensive coverage while maintaining organizational clarity. The standard addresses terminology for major surface analysis techniques including Auger electron spectroscopy (AES), secondary ion mass spectrometry (SIMS), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), elastic peak electron spectroscopy, reflected electron energy loss spectroscopy, and related methods [3] [4]. The 2023 revision has expanded its scope to include emerging methods such as atom probe tomography (APT), near ambient pressure XPS, and hard X-ray photoelectron spectroscopy [5].

Structure and Content Organization

Conceptual Framework

The following diagram illustrates the structural relationship between the different parts of the ISO 18115 standard and the analytical techniques covered by Part 1:

The standard organizes its 630 terms into subject-specific sections, grouping related concepts together to facilitate easier navigation and understanding [5]. This logical arrangement helps users locate terms within specific conceptual frameworks, such as instrumentation, sample preparation, data analysis, or specific measurement concepts.

Quantitative Evolution of Terminology

Table: Evolution of Term Coverage in ISO 18115-1 Revisions

Edition Year	Total Terms	New Additions	Key Focus Areas	Specialized Sections
2010	600 terms [4]	Not specified	Core spectroscopy techniques (AES, XPS, SIMS) [4]	Definitions for surface analysis methods, multivariate analysis [2]
2013	Approximately 900 terms across Parts 1 & 2 [3]	Not specified	Spectroscopy + scanning-probe microscopy [3]	Instrumentation, samples, theoretical concepts [4]
2023	630 terms (Part 1 only) [5]	50+ new terms [5]	Emerging methods, resolution concepts [5]	Resolution description, samples, instruments, analytical concepts [5]

The standard employs specific typographical conventions to enhance usability. Terms printed in boldface within definitions have their own entries elsewhere in the document, creating a interconnected web of related concepts [2]. Additionally, the standard explicitly identifies non-preferred and deprecated terms to guide users toward currently accepted terminology and phase out obsolete usage [2].

Key Changes in the 2023 Revision

The 2023 edition represents a significant update, with more than 70 terms receiving clarifications, modifications, or deletions, and the addition of more than 50 new terms [5]. These changes were implemented in direct response to trends, issues, and needs identified by the surface analysis community.

A particularly important enhancement in the 2023 revision is the standardized description of resolution. The document introduces 25 new and revised terms specifically designed to ensure consistent description of resolution across all surface analysis methods [5]. This addresses a critical need in the field, as resolution terminology previously varied between techniques, causing potential confusion when comparing capabilities across different analytical platforms.

The revision also expands coverage of multivariate analysis terminology, reflecting the growing importance of advanced data processing techniques in modern surface analysis [5]. Additionally, it incorporates terminology related to emerging applications in nanotechnology, ensuring researchers have standardized language for describing nanoscale surface properties and analyses [5].

Experimental Protocols and Implementation

Standardized Analytical Workflow

The following diagram outlines a generalized experimental workflow for surface analysis spectroscopy, highlighting stages where standardized terminology from ISO 18115-1 is critical:

Research Reagent Solutions and Essential Materials

Table: Essential Materials and Reagents for Surface Analysis Spectroscopy

Material/Reagent Category	Specific Examples	Function in Surface Analysis	ISO 18115-1 Relevance
Reference Standard Materials	Gold, copper, sputtered silicon wafers, certified reference materials	Energy scale calibration, intensity calibration, quantification standards	Defines terms for calibration, reference materials, and standard procedures
Sample Mounting Materials	Conductive tapes, specialty holders, custom fixtures	Secure positioning, electrical contact, heat conduction	Standardizes terminology for analysis area, sample orientation, and experimental geometry
Surface Cleaning Reagents	Argon gas sputtering sources, solvent cleaners, plasma cleaners	Surface contamination removal, sample preparation	Defines terms for surface cleanliness, contamination, and preparation methods
Charge Compensation Systems	Low-energy electron floods, argon ion guns, specialized filaments	Charge neutralization in insulating samples	Standardizes terms for charge correction, flood guns, and stabilization methods

Access and Copyright Information

ISO 18115-1:2023 is a copyright-protected document that can be purchased through the ISO website or national standards bodies [1] [3]. However, ISO has granted permission for public access to ISO 18115-1 and ISO 18115-2 for educational and implementation purposes through eight approved websites hosted by scientific institutions in Japan, the UK, USA, Germany, and Spain [3]. These include:

• National Institute of Advanced Industrial Science and Technology (Japan)
• National Physical Laboratory (UK)
• American Vacuum Society (USA)
• Bundesanstalt für Materialforschung und -prüfung (Germany)

Researchers affiliated with these institutions or their partner organizations may be able to access the standards through institutional subscriptions or portals.

Importance in Scientific Research and Drug Development

For researchers, scientists, and drug development professionals, implementation of ISO 18115-1 provides critical benefits for quality assurance and regulatory compliance. In pharmaceutical applications, surface analysis techniques like XPS and SIMS are employed to characterize drug delivery systems, analyze medical device coatings, and study biomaterial interfaces. Using standardized terminology ensures clear communication in research publications, regulatory submissions, and manufacturing quality control.

The standard's comprehensive definitions facilitate more accurate technical documentation and reduce the potential for misinterpretation in multi-disciplinary teams. For drug development professionals, this standardized vocabulary supports compliance with quality-by-design principles and regulatory requirements for material characterization data, particularly when utilizing advanced surface analysis techniques to solve challenging analytical problems in pharmaceutical development.

The International Standard ISO 18115-1:2023 represents a significant evolution in the standardized terminology for surface chemical analysis, reflecting technological advancements and emerging methodologies within the field. This comprehensive revision responds directly to identified trends and needs within the surface analysis community, introducing substantial changes that enhance clarity, consistency, and practical application across spectroscopic techniques [5]. The standard serves as an critical reference for researchers, scientists, and drug development professionals who require precise communication of analytical data and methodologies.

The 2023 edition builds upon previous versions through a systematic review process undertaken by ISO Technical Committee 201 on Surface Chemical Analysis. This revision encompasses modifications to more than 70 existing terms and introduces over 50 new terms, collectively expanding the vocabulary to approximately 630 defined terms and phrases [5]. These definitions cover the samples, instruments, and fundamental concepts central to surface chemical analysis, organized into subject-specific sections to facilitate easier navigation and related term discovery.

Table 1: Summary of Key Changes in ISO 18115-1:2023

Category of Change	Number of Terms	Scope and Impact
Newly Added Terms	>50	Incorporates terminology for emerging methods including atom probe tomography, near ambient pressure XPS, and hard X-ray photoelectron spectroscopy [5].
Revised Terms	>70	Clarifications, modifications, and deletions to existing terminology to reflect current technical understanding and usage [5].
Resolution Terminology	25	New and revised terms to ensure consistent description of resolution across all surface analysis methods [5].
Total Terms in Document	630	Comprehensive coverage of words or phrases used in describing samples, instruments, and concepts in surface chemical analysis [5].

Table 2: Emerging Analytical Methods with Newly Standardized Terminology

Analytical Method	Terminology Category	Research Applications
Atom Probe Tomography (APT)	Structural and compositional analysis at atomic scale	Nanomaterials characterization, interfacial studies in drug delivery systems [5].
Near Ambient Pressure XPS (NAP-XPS)	Spectroscopy under realistic environmental conditions	Catalysis research, in situ monitoring of biological interfaces [5].
Hard X-ray Photoelectron Spectroscopy (HAXPES)	Increased probe depth for bulk-sensitive analysis	Buried interface characterization in multilayer pharmaceutical formulations [5].

Detailed Analysis of Major Terminology Revisions

Standardization of Resolution Terminology

A fundamental advancement in the 2023 edition is the systematic overhaul of resolution terminology, introducing 25 new and revised terms to establish consistent descriptors across all surface analysis methods [5]. This revision addresses previous inconsistencies in how spatial, energy, and mass resolution were defined across different techniques, enabling more accurate cross-method comparisons and technical reporting.

The updated standard provides clarified definitions for terms describing lateral resolution, depth resolution, and energy resolution, with particular attention to their practical measurement and calculation. For techniques like XPS and AES, this includes specific guidance on reporting resolution values in publications and technical documentation. The establishment of consistent metrics allows researchers to more reliably compare instrument capabilities and analytical data across different laboratories and platforms, directly supporting reproducible research in pharmaceutical development and materials science.

Terminology for Emerging Analytical Methods

The 2023 edition significantly expands its coverage of advanced characterization techniques that have gained prominence since the previous version. For atom probe tomography (APT), the standard now defines terms related to detector efficiency, reconstruction parameters, and quantification approaches that are essential for interpreting data from this rapidly evolving technique [5].

For ambient pressure techniques, the standard introduces terminology that distinguishes between various pressure regimes and their effects on measurement conditions. This is particularly relevant for drug development researchers studying surfaces under biologically relevant conditions rather than ultra-high vacuum. The inclusion of hard XPS terminology addresses the growing use of higher energy X-rays for probing buried interfaces and multilayer structures common in advanced drug delivery systems and medical devices.

Experimental Protocols for Terminology Application

Protocol for Resolution Measurement in XPS

Purpose: To standardize the determination of energy resolution in X-ray photoelectron spectroscopy instruments according to ISO 18115-1:2023 definitions.

Materials and Equipment:

• XPS instrument with aluminum/magnesium dual anode or monochromatic X-ray source
• Standard reference sample (clean silver or copper foil)
• Charge neutralization system (if analyzing insulating samples)
• High vacuum system (<1 × 10⁻⁸ Torr)

Procedure:

• Prepare standard silver foil by cleaning with argon ion sputtering (3 keV, 10 μA, 2 minutes) to remove surface contamination.
• Insert sample into analysis chamber and ensure stable temperature (25°C ± 5°C) during measurement.
• For non-monochromatic sources: Acquire Ag 3d₅/₂ peak using Mg Kα X-rays (1253.6 eV) at 10 eV pass energy.
• For monochromatic sources: Acquire Ag 3d₅/₂ peak using Al Kα X-rays (1486.6 eV) at 10 eV pass energy.
• Record the full width at half maximum (FWHM) of the Ag 3d₅/₂ peak with instrumental parameters clearly documented.
• Calculate energy resolution according to the defined methodology in the standard, accounting for both the natural linewidth of the reference peak and the instrumental broadening.

Data Interpretation: Report resolution as FWHM with explicit reference to the measurement conditions, including X-ray source, pass energy, step size, and number of scans, consistent with the updated terminology for spectroscopic resolution [5].

Protocol for Application of Ambient Pressure XPS Terminology

Purpose: To correctly apply terminology from ISO 18115-1:2023 for near ambient pressure XPS (NAP-XPS) experiments.

Materials and Equipment:

• NAP-XPS system with differential pumping of electron analyzer
• High-pressure cell with appropriate X-ray transparent windows
• Pressure calibration system capable of 0.1-20 Torr measurements
• Gas dosing system for controlled environment creation

Procedure:

• Distinguish between "near ambient pressure" (typically 0.1-20 Torr) and "environmental" pressure conditions using the defined thresholds in the standard.
• For sample introduction, utilize the defined terminology for "high pressure transfer mechanism" to maintain experimental integrity.
• When reporting data, specify the "effective analysis depth" rather than simple inelastic mean free path, acknowledging the pressure-dependent scattering effects.
• Document the "pressure transition region" between sample surface and analyzer using the standardized terms for NAP-XPS instrumentation.
• Apply correct terminology for "differential pumping stages" and their impact on detected signal intensity.

Data Interpretation: Use defined terms for describing the pressure-dependent attenuation of photoelectrons and the corresponding changes in surface sensitivity, ensuring consistent reporting across the research community [5].

Conceptual Framework for Terminology Application

Diagram 1: Conceptual Framework of ISO 18115-1:2023 Terminology Structure

Implementation Workflow for Updated Terminology

Diagram 2: Terminology Implementation Workflow for Research Laboratories

Essential Research Reagent Solutions

Table 3: Key Research Reagents and Materials for Surface Spectroscopy

Reagent/Material	Technical Function	Application Context
Reference Standard Materials (Ag, Au, Cu)	Energy scale calibration and resolution verification	Instrument qualification and method validation per standardized terminology [5].
Argon Ion Sputtering Source	Surface cleaning and depth profiling	Sample preparation for surface analysis, requiring precise parameter definition [5].
Charge Neutralization Systems	Surface potential stabilization on insulating samples	Essential for analyzing pharmaceutical powders and polymer-based drug delivery systems [5].
Certified Reference Nanomaterials	Lateral resolution verification and quantification standards	Validation of spatial resolution claims according to updated terminology [5].
High-Pressure Cell Components	Controlled environment maintenance for NAP-XPS	Enables studies under biologically relevant conditions using standardized pressure terminology [5].

Implications for Pharmaceutical Research and Development

The revised terminology in ISO 18115-1:2023 has significant implications for drug development professionals and pharmaceutical researchers. The standardized resolution terminology enables more precise comparison of surface contamination data between contract research organizations and manufacturing facilities. For complex drug formulations involving nano-scale delivery systems, the clarified definitions for techniques like APT and HAXPES provide frameworks for characterizing buried interfaces and multi-component distribution.

The enhanced consistency in terminology supports regulatory submissions by reducing ambiguity in technical documentation. When describing surface modification of drug particles or contamination analysis of medical devices, researchers can now reference internationally recognized definitions that facilitate clearer communication with regulatory agencies. This is particularly valuable for multicenter trials where surface analysis data may be generated at different facilities using various instrumental platforms but must be integrated into a cohesive submission package.

Furthermore, the terminology supporting emerging techniques like NAP-XPS enables pharmaceutical scientists to study surfaces under more physiologically relevant conditions, potentially leading to more predictive analytical models for drug behavior in biological environments. This represents a significant advancement over traditional high-vacuum analysis that may alter surface properties of pharmaceutical materials.

Surface spectroscopy comprises a suite of analytical techniques used to determine the elemental composition, chemical state, and electronic structure of the topmost atomic layers of a sample. These techniques are indispensable in fields ranging from materials science and catalysis to drug development and biomedical research. The ISO 18115-1 standard provides the foundational vocabulary and general terms for surface chemical analysis, ensuring consistency, reproducibility, and clear communication among researchers and scientists [6]. This standard addresses critical terminology for techniques including X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and other surface analysis methods. Navigating this terminology is essential for proper experimental design, data interpretation, and reporting, particularly as the widespread use of these techniques brings challenges related to data reproducibility and accurate interpretation [6]. This guide provides a structured framework for understanding key spectroscopy terms within the context of ISO 18115-1, supported by practical application notes and protocols.

Core Spectroscopy Techniques: Definitions and Applications

Fundamental Categories of Spectroscopy

Spectroscopy techniques are broadly classified based on the nature of the interaction between light (electromagnetic radiation) and matter [7] [8]. The three primary categories are:

• Absorption Spectroscopy: Measures the amount of light absorbed by a sample as a function of wavelength or frequency. The absorption occurs when the energy of the incident light matches the energy required to cause a transition in the atom or molecule to a higher energy state [7].
• Emission Spectroscopy: Involves the measurement of light emitted by excited atoms or molecules as they return to a lower energy state [7].
• Scattering Spectroscopy: Measures the light that is redirected (scattered) when it interacts with particles or molecules. A prominent example is Raman spectroscopy [7].

The following table summarizes the key characteristics of major spectroscopic techniques used in analytical laboratories.

Table 1: Core Spectroscopy Techniques and Their Applications

Technique	Acronym	Principle	Primary Applications	Information Depth
X-ray Photoelectron Spectroscopy [9] [6]	XPS	Measures the kinetic energy of photoelectrons ejected from a sample upon X-ray irradiation to determine elemental composition and chemical state.	Elemental identification, chemical state analysis, oxidation state determination, thin film analysis.	1-10 nm [9]
Auger Electron Spectroscopy [9]	AES	Analyzes the kinetic energy of Auger electrons emitted during the relaxation process following core-level ionization.	Elemental composition mapping, surface contamination studies, thin film analysis.	0.5-5 nm [9]
Ultraviolet Photoelectron Spectroscopy [9]	UPS	Uses UV light to eject electrons from the valence band, probing the density of occupied electronic states.	Work function measurement, valence band structure, molecular orbital energies.	1-2 nm [9]
Ultraviolet-Visible Spectroscopy [7] [10]	UV-Vis	Measures the absorption of ultraviolet and visible light, exciting valence electrons between molecular orbitals.	Concentration determination of solutions, protein quantification, reaction kinetics.	Varies with sample transparency
Infrared Spectroscopy [7] [10]	IR	Measures the absorption of infrared light, which causes molecular vibrations (stretching, bending).	Functional group identification, chemical bond characterization, polymer analysis.	Varies with sample transparency
Raman Spectroscopy [10]	-	Measures the inelastic scattering of light, providing information about molecular vibrations.	Aqueous sample analysis, identification of functional groups complementary to IR.	Varies with sample transparency
Surface-Enhanced Raman Spectroscopy [11]	SERS	Enhances Raman scattering signals by molecules adsorbed on rough metal surfaces or nanostructures.	Trace detection, biosensing, environmental monitoring, food safety.	Single molecule level

Relationships Between Major Spectroscopy Techniques

The following diagram illustrates the logical relationships and primary outputs of the major surface spectroscopy techniques covered by ISO 18115-1.

Experimental Protocols for Surface Spectroscopy

Standard Protocol for X-ray Photoelectron Spectroscopy (XPS)

XPS is a quantitative technique that provides information on elemental composition, empirical formula, chemical state, and electronic state of the elements within a material [9] [6].

Sample Preparation:

• Solid Samples: Mount securely on a suitable holder using double-sided conductive tape or clamps. Ensure good electrical contact to minimize charging.
• Powder Samples: Press into a malleable metal foil (e.g., indium) or spread onto double-sided conductive tape.
• Surface Cleaning: If necessary, clean surfaces in situ via argon ion sputtering or by brief exposure to a solvent vapor [6].
• Handling: Use gloves and tweezers to prevent contamination from skin oils. For air-sensitive samples, use a glove box or vacuum transfer module.

Instrument Setup and Calibration:

• Verify instrument performance and energy calibration using standard samples (e.g., clean gold, silver, or copper foils) [6].
• Select an appropriate X-ray source (typically Al Kα or Mg Kα).
• For insulating samples, engage the charge neutralization system (electron flood gun) [6].

Data Acquisition:

• Survey Spectrum: Acquire over a wide binding energy range (e.g., 0-1100 eV) to identify all elements present [6].
• High-Resolution Spectra: Acquire for core-level regions of identified elements to determine chemical states.
• Parameters: Use a pass energy of 20-80 eV for survey scans and 10-20 eV for high-resolution scans. Step size should be 1.0 eV for survey and 0.05-0.1 eV for high-resolution spectra.
• Charge Referencing: Correct for peak shifts due to charging by referencing to a known peak, such as adventitious carbon (C 1s at 284.8 eV) [9].

Data Analysis Workflow:

• Background Subtraction: Apply a Shirley or Tougaard background to remove the contribution of inelastically scattered electrons [9].
• Peak Identification: Identify elements using core-level binding energy databases.
• Peak Fitting: Decompose overlapping peaks using appropriate line shapes (Gaussian-Lorentzian mixes) and constraints based on chemical knowledge [9].
• Quantification: Calculate atomic concentrations from peak areas using instrument-specific sensitivity factors.

Experimental Workflow for Surface Spectroscopy Analysis

The following diagram outlines the generalized end-to-end workflow for conducting a surface spectroscopy analysis, from planning to reporting.

The Scientist's Toolkit: Essential Reagents and Materials

Successful surface spectroscopy analysis requires the use of specific reagents and materials for sample preparation, calibration, and analysis.

Table 2: Key Research Reagent Solutions for Surface Spectroscopy

Item	Function/Description	Application Notes
Conductive Tapes & Adhesives	Provides a stable and electrically conductive mount for powder and solid samples.	Crucial for preventing charging effects in XPS and AES analysis of non-conductive samples [6].
Standard Reference Materials	Used for instrument calibration and verification of energy scale.	Clean gold (Au 4f₇/₂ at 84.0 eV), silver (Ag 3d₅/₂ at 368.3 eV), and copper (Cu 2p₃/₂ at 932.7 eV) foils are common standards [6].
Inert Transfer Vessels	Allows for the introduction of air-sensitive samples into the spectrometer without exposure to atmosphere.	Essential for analyzing pyrophoric, oxygen-sensitive, or hygroscopic materials [6].
Sputtering Sources	Provides inert gas ions (typically Ar⁺) for in-situ surface cleaning and depth profiling.	Used to remove surface contamination and oxide layers to reveal bulk composition [9].
Charge Neutralizers	Low-energy electron flood gun used to compensate for surface charging on insulating samples.	Standard feature in modern XPS instruments; essential for obtaining meaningful data from polymers, ceramics, and biological samples [6].
Calibrated Electron Detectors	Measures the kinetic energy of ejected electrons with high sensitivity.	The core component of XPS, AES, and UPS systems; performance directly impacts energy resolution and detection limits [9].

Data Analysis and Interpretation in Surface Spectroscopy

Quantitative Analysis and Peak Fitting

Accurate data analysis is critical for extracting meaningful information from surface spectroscopy data.

• Quantification: Elemental concentrations are calculated from the intensities (peak areas) of core-level peaks after correcting for the instrument transmission function and using atomic sensitivity factors [9]. The formula is: ( Cx = \frac{Ix / Sx}{\sum (Ii / Si)} ) where ( Cx ) is the atomic concentration of element x, ( Ix ) is the measured peak area, and ( Sx ) is the atomic sensitivity factor.

• Peak Fitting: This process involves deconvoluting overlapping peaks into individual components representing different chemical environments [9]. Key steps include:

  • Choosing an appropriate background (e.g., linear, Shirley, or Tougaard).
  • Selecting a suitable line shape (e.g., Gaussian-Lorentzian product form).
  • Applying constraints based on chemical knowledge, such as fixed spin-orbit splitting and intensity ratios.

• Chemical State Identification: Shifts in core-level binding energies provide information about the chemical state and oxidation state of an element. For example, the Si 2p peak shifts to higher binding energy as silicon transitions from its elemental form to SiO₂ [9].

Advanced Data Interpretation Concepts

• Valence Band Spectroscopy: UPS is specifically used to probe the valence band region, which reflects the occupied density of states and provides information about the electronic structure, including the work function and ionization potential [9].
• Depth Profiling: Combining surface spectroscopy with controlled ion sputtering allows for the determination of composition as a function of depth, essential for analyzing thin films, interfaces, and corrosion layers [9].
• Hyperspectral Imaging: Acquiring spectra at every pixel in a defined area creates a chemical map, revealing the lateral distribution of elements and chemical states across a surface.

A precise understanding of the terms and concepts outlined in ISO 18115-1 is fundamental for the correct application of surface spectroscopy techniques. From selecting the appropriate method (XPS, AES, UPS, etc.) and following rigorous experimental protocols to conducting meticulous data analysis, each step requires careful consideration of standardized terminology and best practices. The frameworks, protocols, and toolkits provided in this document serve as a guide for researchers and scientists to navigate the complex landscape of surface spectroscopy, thereby enhancing the reliability, reproducibility, and impact of their research in drug development and material science.

The field of surface chemical analysis is a cornerstone of modern materials science, nanotechnology, and drug development. Its power to characterize material composition and structure, however, is dependent on a shared, precise language that ensures clarity and reproducibility across research and industrial applications. The International Standard ISO 18115-1:2023 provides this essential vocabulary, defining general terms and those used in spectroscopy for surface chemical analysis [1]. This document is dynamic, having been recently revised with clarifications, modifications, and deletions to more than 70 terms and with the addition of more than 50 new terms. These updates respond directly to technological trends and community-identified needs, encompassing emerging methods such as atom probe tomography (APT), near ambient pressure XPS, and hard X-ray photoelectron spectroscopy [5].

The standard collates over 630 terms into subject-specific sections, covering the samples, instruments, and fundamental concepts involved in surface analysis [5]. Adherence to this standardized terminology is not merely academic; it is a practical necessity. It prevents misinterpretation in technical communications, ensures data integrity, and facilitates reliable comparison of results across different laboratories and instrument platforms. For researchers and drug development professionals, using this common vocabulary is crucial for documenting findings in regulatory submissions, publishing in peer-reviewed journals, and collaborating effectively in multidisciplinary teams. This application note distills the core concepts from this extensive standard, focusing on the essential terminology related to samples, instruments, and data.

Core Terminology for Samples

Sample Properties and Definitions

In surface chemical analysis, precise characterization begins with a clear understanding of the sample itself. The following table outlines key terms used to describe sample properties and states.

Table 1: Essential Terminology for Sample Properties

Term	Definition / Description	Relevance in Analysis
Surface	The outer-most several atomic layers of a solid, typically where the analysis information originates.	Defines the region of interest for techniques like XPS and AES [3].
Nanomaterial	A material with any external dimension in the nanoscale or having an internal or surface structure in the nanoscale.	Critical for classification in drug delivery systems and nanotechnology applications [5].
Band Gap	The electron energy difference between the top of the valence band and the bottom of the conduction band in a semiconductor [12].	Determines sample conductivity and charging behavior during electron or ion bombardment.
Analyte	The component of a sample that is the subject of measurement.	Focuses the analytical goal on a specific element, molecule, or material phase.

Sample Preparation and Handling

The preparation of a sample can profoundly influence the analytical outcome. Key concepts include:

• Reference Sample: A sample with known properties used for instrument calibration or to verify analytical performance. The use of such samples is fundamental to establishing the validity of data obtained from unknown samples.
• Sample Drift: The unintended movement of the sample relative to the probe beam during analysis. Minimizing drift is essential for achieving high spatial resolution, especially in mapping or depth profiling experiments.

Essential Instrumentation Terminology

Analytical Techniques and Components

Surface spectroscopy relies on a suite of sophisticated techniques, each with its own operational principles defined by ISO 18115-1.

Table 2: Core Techniques and Instrument Components

Term / Technique	Acronym	Core Principle / Function
X-ray Photoelectron Spectroscopy	XPS	Measures the kinetic energy of electrons ejected from a sample upon irradiation with X-rays to determine elemental composition and chemical state [3].
Auger Electron Spectroscopy	AES	Involves the analysis of energetic electrons emitted from an excited atom after a radiationless transition, used for elemental analysis and depth profiling [3].
Secondary Ion Mass Spectrometry	SIMS	Uses a primary ion beam to sputter and ionize atoms and molecules from the surface, which are then analyzed by a mass spectrometer [3].
Mass Analyzer	-	The section of a mass spectrometer in which ions are differentiated based on their mass-to-charge (m/z) ratios [13].
Analog-to-Digital Converter	ADC	A component responsible for converting the voltage from a detector (e.g., from photons or electrons) into a digital signal for processing and display [12].
Aberration	-	A departure in optical system performance from ideal models, leading to effects like blurred spectra. Types include chromatic, coma, and spherical aberration [12].

Resolution and Performance Metrics

A critical update in ISO 18115-1:2023 is the consolidation of 25 terms to ensure consistent description of resolution across all surface analysis methods [5]. Understanding these metrics is vital for selecting the right instrument and interpreting data correctly. Key resolution types include:

• Spectral Resolution: The ability of a spectrometer to distinguish two adjacent spectral features.
• Spatial Resolution: The smallest distance between two features that can still be distinguished as separate in a spatial map.
• Mass Resolution: In mass spectrometry, the ability to distinguish between two ions with a small mass difference, often defined as M/ΔM, where M is the ion mass and ΔM is the peak width.

Key Concepts for Data Interpretation and Analysis

Fundamental Data Properties

The data generated by surface analysis instruments must be interpreted using well-defined concepts to extract meaningful chemical information.

• Absorbance (A): A dimensionless unit (AU) quantifying how much light a sample absorbs. It is defined by the Beer-Lambert Law as A = εlc, where ε is the absorptivity, l is the path length, and c is the concentration. This makes absorbance directly proportional to concentration, a cornerstone of quantitative analysis [12].
• Signal-to-Noise Ratio (SNR): A measure that compares the level of a desired signal to the level of background noise. It can be improved through averaging, where the SNR increases by the square root of the number of spectral scans averaged [12].
• Base Peak: In a mass spectrum, the ion peak with the highest relative abundance. All other peak abundances in the spectrum are normalized to this peak, which is assigned a value of 100% [13].
• Accurate Mass: The calculated exact mass of an ion based on the specific isotopic composition of its constituent atoms. It allows for the deduction of an ion's empirical formula [13].

Data Processing and Calibration Terms

Raw data often requires processing and calibration to yield accurate results.

• Baseline Offset: The signal level reported by an instrument when no sample or light is present. It is a composite of electronic offset, dark current, and readout noise [12].
• Baseline Drift: The deviation in the average baseline offset caused by temperature changes, which can affect the stability of quantitative measurements over time [12].
• Calibration: The process of adjusting and certifying a spectrometer's operation using a standard of known properties to ensure it produces accurate results, such as correct ion masses or wavelength values [13].
• Dynamic Range: The range over which an instrument can provide a linear and quantitative response, from the lowest detectable signal to the signal level at which saturation occurs.

Experimental Protocols and Workflows

Protocol: Quantitative Elemental Analysis via XPS

This protocol outlines the key steps for performing a quantitative elemental analysis of a solid sample using X-ray Photoelectron Spectroscopy (XPS), adhering to standardized terminology.

1. Sample Preparation:

• Mount the sample on a suitable holder using double-sided conductive tape or a metal clip.
• If the sample is insulating, note the potential for charging and the possible need for a charge neutralization system.
• Insert the sample into the introduction chamber and pump down to high vacuum (< 10^-6 mbar) before transferring to the analysis chamber.

2. Instrument Calibration & Setup:

• Perform an energy calibration of the spectrometer using a reference sample, such as clean gold or copper foil. The Au 4f7/2 peak should be at a binding energy of 84.0 eV.
• Set the X-ray source (e.g., Al Kα or Mg Kα) and the pass energy of the analyzer. A lower pass energy provides higher spectral resolution, while a higher pass energy offers better signal intensity.
• Ensure the analysis chamber has reached ultra-high vacuum (UHV, typically < 10^-8 mbar) to minimize surface contamination.

3. Data Acquisition:

• Acquire a wide (or survey) scan to identify all elements present on the sample surface.
• Acquire high-resolution multiplex scans for each identified element to determine their chemical states and for accurate quantification.
• Set appropriate acquisition parameters (number of scans, dwell time) to achieve a sufficient Signal-to-Noise Ratio (SNR).

4. Data Processing and Quantification:

• Apply a linear or Shirley background subtraction to the high-resolution peaks to isolate the peak area.
• Integrate the area under each photoelectron peak.
• Calculate the atomic concentration (in %) of each element using relative sensitivity factors (RSFs) provided by the instrument manufacturer or standard databases, using the formula: Atomic Concentration (%) = (Peak Area / RSF) / Σ(All Peak Areas / RSFs) * 100%

5. Reporting:

• Report all identified elements and their atomic percentages.
• Note the instrumental conditions used (X-ray source, analyzer pass energy, etc.).
• Report the peak fitting parameters for high-resolution spectra, including the background type and peak full width at half maximum (FWHM).

Diagram 1: XPS quantitative analysis workflow

The Scientist's Toolkit: Key Research Reagents and Materials

The following table details essential materials and their functions in surface spectroscopy experiments.

Table 3: Essential Research Reagents and Materials for Surface Spectroscopy

Item / Reagent	Function / Application
Certified Reference Materials (CRMs)	Samples with certified composition and homogeneity used for instrument calibration, method validation, and quality control. Examples include gold foil for XPS energy calibration and silicon wafers with thermal oxide for sputter depth profiling.
Conductive Tapes & Adhesives	Used for mounting powder or non-conductive samples to a sample stub to ensure electrical and thermal contact with the holder, minimizing sample charging.
Charge Neutralization Flood Gun	A source of low-energy electrons or ions used to neutralize positive charge built up on insulating samples during analysis with charged particle beams (e.g., in XPS or AES).
Ultra-High Purity Sputter Gases (Ar, Xe)	Inert gases used in ion sources for sample cleaning and depth profiling by removing surface layers via sputtering.
Standard Samples for Sensitivity Factors	Samples of known, pure materials used to determine the relative sensitivity factors (RSFs) necessary for quantitative analysis in techniques like XPS and AES.

The precise and consistent use of terminology as defined in ISO 18115-1:2023 is the bedrock upon which reliable and reproducible surface chemical analysis is built. This application note has detailed the core concepts pertaining to samples, instruments, and data, providing a foundational resource for researchers and drug development professionals. From understanding sample properties like band gap and preparing a reference sample, to operating instruments and interpreting data through concepts like absorbance, signal-to-noise ratio, and base peak, this standardized vocabulary enables clear communication and robust scientific practice. As the field continues to evolve with new techniques, maintaining a commitment to this standardized language will be essential for driving innovation, ensuring data integrity, and facilitating successful collaboration across the scientific community.

From Theory to Practice: Applying ISO 18115-1 in Real-World Biomedical Research

Within the field of surface spectroscopy research, consistent terminology is paramount for accurate communication, data reproducibility, and scientific advancement. This document outlines technique-specific terminology and application protocols for X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES), and Secondary Ion Mass Spectrometry (SIMS), framed within the overarching context of the ISO 18115-1:2023 standard [1]. This international standard, titled "Surface chemical analysis — Vocabulary," provides the foundational definitions and general terms that ensure methodological rigor across the discipline. The following sections translate these general principles into detailed application notes and standardized protocols for these three key techniques, providing researchers with a unified framework for experimental design and reporting.

X-ray Photoelectron Spectroscopy (XPS)

Core Terminology and Principles

X-ray Photoelectron Spectroscopy (XPS) is a surface-sensitive quantitative spectroscopic technique that measures the elemental composition, chemical state, and electronic structure of the very topmost 5–10 nm (approximately 50–60 atomic layers) of a material [14]. The technique is based on the photoelectric effect, where irradiating a material with a beam of X-rays causes the emission of electrons. The foundational equation for XPS is:

• Binding Energy (E_binding): The energy of an electron within its atomic orbital, measured relative to the sample's Fermi level. It is calculated as E_binding = E_photon - (E_kinetic + φ), where E_photon is the energy of the X-ray photons, E_kinetic is the measured kinetic energy of the electron, and φ is the work function of the spectrometer [14].

Table 1: Key Quantitative Parameters in XPS Analysis

Parameter	Typical Range or Value	Description
Analysis Depth	5 - 10 nm	Information depth for the detected electrons [14].
Typical Vacuum	Ultra-High Vacuum (UHV), < 10⁻⁷ Pa	Prevents scattering of electrons and sample contamination [14].
Detection Limit	0.1 - 1.0 atomic % (1000 - 10000 ppm)	Varies with element cross-section and background; ppm achievable with long collection times [14].
Spatial Resolution	≥ 10 - 200 µm (Lab sources); ~200 nm (Synchrotron)	Minimum analysis area for laboratory and advanced imaging instruments [14].
Common X-ray Sources	Al Kα (1486.7 eV), Mg Kα (1253.7 eV)	Monochromatic sources provide higher energy resolution [14].

Experimental Protocol for Routine Surface Analysis

Objective: To determine the elemental composition and chemical states of a solid material's surface.

Materials and Reagents:

• Sample: Solid, vacuum-compatible material (conducting or insulating).
• Sample Mounting: Standard XPS stub (e.g., 1 cm diameter), conductive double-sided tape or metal clamps.
• Reference Sample: Clean gold or silver foil for instrument performance verification.

Procedure:

• Sample Preparation:
  • Cut the sample to fit the analysis stub.
  • If possible, clean the surface using solvents or in-situ methods (e.g., argon sputtering) to remove adventitious carbon contamination.
  • Mount the sample securely to ensure good electrical contact.

• Loading and Pump-down:

  • Introduce the sample into the UHV load-lock chamber.
  • Evacuate the load-lock to a pressure below 10⁻⁵ Pa before transferring to the main analysis chamber.
  • Allow the analysis chamber to reach base pressure (< 10⁻⁷ Pa) before initiating analysis.

• Data Acquisition:

  • Survey Spectrum: Collect a wide energy range scan (e.g., 0-1200 eV binding energy) with low energy resolution to identify all elements present. Typical acquisition time: 1-20 minutes [14].
  • High-Resolution Regional Scans: For each element of interest, perform a high-resolution scan over a narrow energy range. Use a lower pass energy for greater resolution. Typical acquisition time: 1-15 minutes per region [14].
  • Charge Neutralization: For insulating samples, activate the low-energy electron flood gun to compensate for surface charging.

• Data Analysis:

  • Identify elements from the survey spectrum using characteristic peak positions (e.g., C 1s, O 1s, N 1s).
  • For high-resolution spectra, perform a background subtraction (e.g., Shirley or Tougaard background) and curve-fitting to deconvolute different chemical states.
  • Calculate atomic concentrations by integrating peak areas and correcting with relative sensitivity factors (RSFs).

Workflow Visualization

Auger Electron Spectroscopy (AES)

Core Terminology and Principles

Auger Electron Spectroscopy (AES) is a surface-sensitive analytical technique that uses a focused electron beam to excite atoms, leading to the emission of Auger electrons. The kinetic energy of these electrons is characteristic of the element from which they originated, allowing for elemental identification and, in some cases, chemical state information. While the search results provided information on the Advanced Encryption Standard (also abbreviated AES), the definitions here are based on the established principles of Auger Electron Spectroscopy within the surface analysis field, consistent with the scope of ISO 18115-1 [1]. The key transitions are labeled using the Auger notation (e.g., KL₁L₂₃), which describes the atomic energy levels involved in the process.

Table 2: Key Parameters and Typical Experimental Conditions for AES

Parameter	Typical Range or Value	Description
Primary Electron Beam Energy	3 - 25 keV	Energy of the incident electron beam used for excitation.
Spatial Resolution	< 10 nm (Modern FEG-AES)	Determined by the diameter of the primary electron beam.
Analysis Depth	2 - 5 nm	Escape depth of Auger electrons, similar to XPS.
Detection Limit	~0.1 - 1 atomic %	Varies with element and matrix.
Vacuum Requirement	Ultra-High Vacuum (UHV), < 10⁻⁷ Pa	Essential for surface sensitivity and electron beam stability.

Experimental Protocol for Elemental Mapping and Depth Profiling

Objective: To perform high-spatial-resolution elemental mapping and depth-resolved compositional analysis of a solid surface.

Materials and Reagents:

• Sample: Conducting or semi-conducting solid material.
• Reference Sample: Si wafer with patterned or known thin film structure for spatial resolution calibration.
• Sputter Ion Source: Argon (Ar⁺) ion gun for depth profiling.

Procedure:

• Sample Preparation and Loading:
  • Follow a similar procedure as for XPS (Section 2.2), ensuring the sample is grounded to prevent charging. For insulating samples, a thin metal coating may be necessary.

• Instrument Setup:

  • Select a primary electron beam energy appropriate for the analysis (e.g., 10 keV).
  • Focus the electron beam on the area of interest. Use a Faraday cup to measure the beam current accurately.

• Data Acquisition:

  • Point Analysis: Position the beam on a specific feature and acquire a survey spectrum to identify elements present.
  • Elemental Mapping: Raster the focused electron beam over a defined area while recording the intensity of a specific Auger peak at each pixel. This generates a 2D spatial distribution map of the element.
  • Depth Profiling: Alternate between data acquisition (point or map) and material removal using a focused Ar⁺ ion beam. The sputter rate must be calibrated using a standard of known thickness (e.g., SiO₂ on Si).

• Data Analysis:

  • Identify elements from the characteristic kinetic energies in the survey spectrum.
  • Quantify elemental concentrations using relative sensitivity factors.
  • Construct depth profiles by plotting atomic concentration as a function of sputter time (converted to depth).

Research Reagent Solutions for Surface Analysis

Table 3: Essential Materials for XPS and AES Experiments

Item	Function / Application
Conductive Tapes & Pastes	Provides electrical contact and secure mounting of samples to stubs, crucial for charge compensation.
Argon Gas (High Purity)	Source for ion guns used for sample cleaning and depth profiling via sputtering.
Standard Reference Materials	Used for instrument calibration and quantification (e.g., pure Au, Ag for energy scale; SiO₂/Si for sputter rate).
In-situ Sample Cleaver	Allows for the creation of atomically clean surfaces inside the UHV environment, free from atmospheric contamination.
Low-Energy Electron Flood Gun	Essential for charge neutralization on insulating samples (e.g., polymers, ceramics) during XPS/AES analysis.

Secondary Ion Mass Spectrometry (SIMS)

Core Terminology and Principles

Secondary Ion Mass Spectrometry (SIMS) is a highly sensitive surface analysis technique that uses a focused primary ion beam to sputter and ionize atoms and molecules from the outermost layers of a solid surface. The emitted secondary ions are then mass-analyzed to determine the elemental, isotopic, or molecular composition of the surface. SIMS is characterized by its excellent detection limits (parts-per-billion to parts-per-million range) and its capability for high-resolution spatial imaging and depth profiling. The technique is categorized into static SIMS (for monolayer surface analysis) and dynamic SIMS (for rapid removal and bulk analysis or deep depth profiling).

Table 4: Key Parameters and Modes of SIMS Analysis

Parameter	Static SIMS	Dynamic SIMS
Primary Ion Dose	< 10¹³ ions/cm² (preserves monolayer)	> 10¹³ ions/cm²
Information Depth	1 - 2 monolayers	Continuously eroded surface
Primary Ion Types	Clusters (e.g., C₆₀⁺, Arn⁺), Ga⁺	O₂⁺, Cs⁺, O⁻
Lateral Resolution	~100 nm - 1 µm	~1 µm - sub-µm
Main Application	Molecular surface speciation, organic materials	Elemental depth profiling, trace impurity analysis

Experimental Protocol for Static SIMS Analysis of Organic Surfaces

Objective: To characterize the molecular composition of the top monolayer of an organic material (e.g., a pharmaceutical formulation or polymer) without causing significant surface damage.

Materials and Reagents:

• Sample: Solid organic/polymer film or active pharmaceutical ingredient (API).
• Substrate: Clean silicon wafer.
• Primary Ion Source: Cluster ion source (e.g., Bi_n⁺, C₆₀⁺, Ar_n⁺).

Procedure:

• Sample Preparation:
  • Prepare a thin, uniform film of the material on a Si wafer using spin-coating, drop-casting, or vapor deposition.
  • Ensure the sample is dry and free of volatile contaminants.

• Loading and Pump-down:

  • Load the sample into the UHV SIMS instrument.
  • Pump down to the analysis pressure (typically < 10⁻⁷ Pa).

• Instrument Setup:

  • Select a cluster ion source (e.g., Bi₃⁺) to enhance the yield of high-mass molecular ions and minimize fragmentation.
  • Set the primary ion beam energy and current to a low dose to ensure static conditions.
  • Adjust the mass spectrometer (Time-of-Flight, ToF, is common for static SIMS) for high mass resolution.

• Data Acquisition:

  • Acquire a mass spectrum over a wide mass range (e.g., m/z 1-2000).
  • For spatial distribution, acquire ion images by rastering the primary ion beam and recording the position and mass of each detected secondary ion.

• Data Analysis:

  • Assign peaks in the mass spectrum to specific molecular fragments and adducts.
  • Generate chemical maps by selecting specific masses of interest from the imaging dataset.
  • Use multivariate analysis techniques (e.g., PCA) to handle complex spectral data.

Technique Selection Workflow

Within the framework of ISO 18115-1, which defines general terms for surface chemical analysis, the consistent use of terminology is paramount for ensuring data comparability and technical reproducibility. This case study examines the application of these standardized terms in the context of Near-Ambient Pressure X-ray Photoelectron Spectroscopy (NAP-XPS), a technique that extends traditional XPS to investigate samples under conditions beyond ultra-high vacuum (UHV). By framing the technical specifications and experimental protocols of NAP-XPS using standardized language, this document provides a model for clear communication among researchers, scientists, and drug development professionals engaged in surface spectroscopy research.

Conventional X-ray Photoelectron Spectroscopy (XPS) is a surface-sensitive quantitative spectroscopic technique that measures the elemental composition, empirical formula, and chemical state of elements within a material. However, it requires high vacuum conditions (P ~ 10⁻⁸ mbar), making it unsuitable for studying surfaces under real-world conditions, such as during catalytic reactions or in the presence of vapors [15]. NAP-XPS addresses this limitation by enabling analysis at pressures of a few tens of mbar, allowing researchers to probe chemical interactions at the atomic level for vapor/solid interfaces [15] [16].

The core of a NAP-XPS system is a specially designed hemispherical energy analyzer coupled with a differentially pumped electrostatic pre-lens system. This configuration allows the analyzer to maintain the necessary vacuum for electron detection while the sample is exposed to higher-pressure environments [15]. The following table summarizes the key operational parameters of a typical NAP-XPS system.

Table 1: Key Technical Specifications of a Representative NAP-XPS System

Parameter	Specification	Technical Notes
Pressure Range	From ~10⁻¹⁰ mbar up to 20-100 mbar [17] [15]	Enables studies from UHV to near-ambient conditions.
Temperature Range	From -200 K to 1000 K [15]	Allows for investigation of temperature-dependent processes.
Analyser Type	PHOIBOS 150 Hemispherical Energy Analyzer [17] [15]	Equipped with differentially pumped lenses.
X-ray Source	Monochromated Al Kα source [15]	Provides high-intensity, focused X-ray excitation.
System Configurations	Backfilling, In-situ reaction cell (e.g., DeviSim), Exchangeable analysis chambers [17]	Offers flexibility for different experimental needs.

Experimental Protocols and Methodologies

Core NAP-XPS Experimental Workflow

A typical NAP-XPS experiment involves a sequence of steps designed to ensure sample integrity and data quality. The workflow below outlines the core methodology for conducting an in-situ gas-solid interaction study, a common application of NAP-XPS.

Diagram 1: Core NAP-XPS experimental workflow for in-situ studies.

Detailed Stepwise Protocol

This protocol elaborates on the workflow for a study of a catalytic material under reactive gas conditions.

• Sample Preparation and Introduction:

  • Prepare the solid sample (e.g., a catalyst pellet or thin film) as required. Clean the sample surface, potentially using in-situ methods such as argon ion sputtering available in the preparation chamber [15].
  • Transfer the sample into the analysis chamber via the load-lock chamber. The load-lock prevents the main analysis chamber from being exposed to ambient atmosphere, preserving the UHV baseline [15].

• Baseline Characterization under UHV:

  • With the analysis chamber at a base pressure of ~10⁻¹⁰ mbar, perform an initial XPS survey and high-resolution scans of the relevant elements.
  • This baseline measurement is critical for identifying any changes in chemical states that occur upon introduction of the gas environment.

• Introduction of Ambient Pressure Environment:

  • Introduce the process gas (e.g., O₂, CO, H₂) or vapor into the system. This can be done via two primary methods:
    • Backfilling: The entire analysis chamber is filled with gas [17].
    • In-situ Cell: A smaller reaction cell (e.g., DeviSim) installed within the analysis chamber is used. This configuration minimizes the reaction volume and is efficient for gas studies [17] [15].
  • Precisely regulate the gas pressure using leak valves or mass flow controllers, stabilizing it at the desired value (e.g., 1-20 mbar).

• Operando NAP-XPS Data Acquisition:

  • With the sample under the target pressure and temperature, acquire XPS data.
  • The monochromated X-ray source irradiates the sample, and emitted electrons travel through the differentially pumped lenses of the PHOIBOS 150 analyzer, which measures their kinetic energy [15].
  • A key advantage of NAP-XPS is that charge compensation occurs naturally through the ionization of the residual/background gas by the incident X-rays, often yielding high-resolution spectra without the need for an additional electron flood gun [16].

• Parameter Modulation and Data Collection:

  • Systematically vary experimental parameters to study dynamic processes. A common approach is to increase the sample temperature (up to 1000 K) while continuously acquiring XPS spectra to observe temperature-dependent chemical state changes [15].
  • The gas composition can also be altered to simulate reaction conditions.

• Data Analysis:

  • Analyze the collected spectra using standard XPS data processing software, focusing on peak fitting, quantitative analysis, and tracking chemical shift changes as a function of the experimental conditions.

The Scientist's Toolkit: Essential Research Reagent Solutions

The following table details key components and materials essential for conducting NAP-XPS experiments, aligned with standardized terminology from ISO 18115-1.

Table 2: Essential Materials and Components for NAP-XPS Experiments

Item	Standardized Function / Role	Application Notes
PHOIBOS 150 NAP Analyzer	Hemispherical energy analyzer with differential pumping.	Enables electron energy analysis in elevated pressure environments (up to 100 mbar) [17] [15].
DeviSim In-situ Reaction Cell	Miniaturized reaction chamber within the analysis chamber.	Confines gas close to the sample, enabling high local pressures with a smaller gas load [17].
Monochromated Al Kα X-ray Source	Laboratory source for X-ray excitation.	Provides high-intensity, focused X-rays for improved spectral resolution [15].
Electrochemical Cell	Sample holder for in-situ electrochemical bias.	Allows for the study of electrode-electrolyte interfaces under controlled potential [15].
NAP Cluster Flange	Interface flange for modular system design.	Provides optimized mounting for analyzer and X-ray source, allowing for easy exchange of analytical chambers, particularly at synchrotron facilities [17].
Process Gases (e.g., O₂, CO, H₂)	Reactive or inert atmosphere introduction.	Creates the desired chemical environment for operando studies of catalysis, corrosion, or vapor/solid interactions.

System Configuration and Signal Flow

Understanding the physical configuration of a NAP-XPS system is crucial for planning experiments and interpreting data. The block diagram below illustrates the main components and the path of signal (electrons) from the sample to the detector.

Diagram 2: NAP-XPS system components and electron signal path.

Within the domain of surface spectroscopy research, the precise definition and consistent measurement of resolution are foundational for generating reliable, comparable, and decision-ready data. This parameter, whether it pertains to spatial, spectral, or energy resolution, directly influences the interpretation of material properties, from chemical composition to morphological structure. The ISO 18115-1 standard, which provides general terms and definitions for surface chemical analysis, establishes a critical framework for this terminology [18]. However, the practical application of these definitions across diverse measurement techniques (e.g., FTIR, Raman, ICP-MS) presents a significant challenge for researchers and drug development professionals. Discrepancies in measurement methodologies can lead to inconsistencies in reported resolution values, potentially compromising data integrity and hindering the replication of studies.

This application note addresses the imperative for methodological harmonization. It provides a detailed guide for defining, measuring, and reporting resolution in alignment with ISO 18115-1 principles. By summarizing quantitative data into structured tables and outlining explicit experimental protocols, this document aims to equip scientists with the tools necessary to ensure consistency and uphold the highest standards of analytical rigor in surface spectroscopy research.

Theoretical Foundation: Resolution in Surface Spectroscopy

Resolution, in the context of ISO 18115-1, refers to the ability of an analytical instrument to distinguish between two adjacent signals. These signals can be spectral peaks, spatial features, or energy levels. The standard provides the definitive terminology to avoid ambiguity; for instance, distinguishing between "spectral resolution" (ability to resolve nearby peaks in a spectrum) and "spatial resolution" (ability to resolve adjacent features in space) is crucial for clear communication [18].

The following diagram illustrates the core logical relationship between the overarching goal of measurement consistency and the key factors that influence resolution, as defined by standard practices.

Key Influencing Factors

The achievement of high and consistent resolution is not a function of a single parameter but is governed by a complex interplay of factors, which can be categorized as follows:

• Instrumental Factors: These are inherent to the design and operation of the spectrometer. They include optical slit widths, which control the amount of light entering the system; the size and sensitivity of the detector elements; the numerical aperture of the focusing lenses or objectives; and the stability of the light source or electron beam. For techniques like FTIR microscopy, innovations in imaging and automation are continuously refining control over these factors [19].
• Sample Properties: The sample itself can significantly impact the measured resolution. Surface roughness, electrical conductivity, chemical heterogeneity, and topographic features can all broaden signals or introduce artifacts, effectively degrading the practical resolution below the instrumental capability. This is particularly critical in the analysis of complex pharmaceutical formulations or layered materials.
• Data Processing: The methods used to process spectral data can enhance or obscure resolution. Operations such as smoothing, Fourier transformation, baseline correction, and peak deconvolution must be applied consistently and documented thoroughly. Over-processing can artificially inflate apparent resolution, leading to non-reproducible results.

Measurement Methods and Quantitative Comparison

Different spectroscopic techniques prioritize and quantify resolution in distinct ways. The table below provides a comparative overview of how resolution is defined and typically measured across common surface analysis methods.

Table 1: Quantitative Comparison of Resolution Metrics Across Spectroscopic Techniques

Technique	Resolution Type	Key Metric(s)	Typical Range	Standard Reference Material
FTIR Spectroscopy	Spectral	Full Width at Half Maximum (FWHM)	0.5 cm⁻¹ - 8 cm⁻¹ [19]	Polystyrene film
Raman Microscopy	Spatial & Spectral	Spot Size (µm), FWHM (cm⁻¹)	Sub-micrometer [18]	Silicon wafer
ICP-MS	Mass	FWHM (amu)	< 0.8 amu [19]	Multi-element solution (e.g., Li, Y, Ce, Tl)
UV-Vis Spectroscopy	Spectral	FWHM (nm)	0.1 nm - 5 nm	Holmium oxide solution
XPS (ESCA)	Energy	FWHM (eV)	0.5 eV - 1.2 eV	Clean gold foil (Au 4f₇/₂)

The fundamental metric uniting most of these methods is the Full Width at Half Maximum (FWHM). This is measured by examining an isolated, sharp peak from a standard reference material. The width of the peak at half of its maximum intensity is calculated, providing a direct, reproducible value for the instrument's resolving power under those specific conditions.

Experimental Protocols for Resolution Verification

To ensure consistency, regular verification of resolution using standardized protocols is essential. The following workflow details a general procedure applicable to many techniques, with technique-specific notes provided.

Detailed Protocol: Spectral Resolution Measurement via FTIR

1. System Preparation

• Power on the FTIR spectrometer and associated microscope, allowing a minimum of 60 minutes for the infrared source and detector to stabilize.
• Purge the optical path with dry, CO₂-free nitrogen to minimize atmospheric absorption interferences.
• Configure the instrument software to the standard resolution verification method, typically using a resolution of 4 cm⁻¹, 32 scans, and a mirror velocity of 2.8 kHz.

2. Standard Acquisition

• Obtain a certified polystyrene film standard.
• Place the standard in the sample holder and ensure it is positioned correctly in the beam path for transmission or ATR analysis.
• Collect the background spectrum.
• Acquire the sample spectrum of the polystyrene standard. For microscope systems, specify the aperture size used.

3. Data Analysis

• Identify the sharp peak located at approximately 1601 cm⁻¹ in the polystyrene spectrum.
• Use the software's peak analysis tool to calculate the Full Width at Half Maximum (FWHM) of this peak.
• Record the measured FWHM value.

4. Result Documentation and Acceptance Criteria

• The resolution verification is considered acceptable if the FWHM at 1601 cm⁻¹ falls within the manufacturer's specified tolerance (e.g., ±0.2 cm⁻¹ of the defined instrument resolution).
• Document all parameters in a lab notebook or LIMS, including: Date, Instrument ID, Operator, CRM ID, Measured FWHM, and any deviations from the standard procedure.

The Scientist's Toolkit: Essential Research Reagents and Materials

The following table details key materials and reagents required for the consistent application of resolution measurement protocols.

Table 2: Key Research Reagent Solutions for Resolution Verification

Item	Function & Application	Technical Notes
Certified Reference Materials (CRMs)	Provides a known, stable signal with sharp, well-characterized peaks for accurate FWHM measurement.	Essential for all techniques. Examples: Polystyrene for FTIR, Silicon for Raman, Gold foil for XPS. Must be traceable to national standards.
Stable Multi-Element Tuning Solutions	Used in ICP-MS for mass resolution calibration and sensitivity optimization across the mass range.	Contains elements like Lithium (Li), Yttrium (Y), and Thallium (Tl) at certified concentrations [19].
Non-Fluorescent Specimen Plate	Provides a flat, low-background substrate for mounting samples in microscopic techniques (Raman, FTIR microscopy).	Critical for achieving reliable spatial resolution measurements and minimizing background noise.
High-Purity Solvents	Used for sample dilution, cleaning optics, and preparing standard solutions without introducing spectral contaminants.	Includes HPLC-grade water, spectral-grade acetone, and isopropanol.
Contamination-Free Sample Handling Kit	Ensures the integrity of samples and standards during preparation to prevent artifacts that can degrade resolution.	Includes ceramic tweezers, gloves [20], and clean-room wipes to avoid introduction of silicones or other contaminants.

The path to reliable surface spectroscopy research is paved with consistent and accurately defined measurements. By adhering to the principles outlined in ISO 18115-1 and implementing the standardized protocols and verification procedures detailed in this application note, researchers and drug development professionals can significantly enhance the quality, comparability, and credibility of their analytical data. A rigorous, standardized approach to defining and verifying resolution is not merely a technical formality but a fundamental prerequisite for scientific advancement in the field.

The integration of surface spectroscopy with scanning-probe microscopy (SPM) represents a paradigm shift in materials characterization, enabling simultaneous correlation of nanoscale physical topography with chemical information. This multimodal approach addresses fundamental limitations of individual techniques by providing spatially co-registered data sets that reveal how local chemistry and structure drive macroscopic functionality. Within the framework of ISO 18115-1, which defines general terms for surface chemical analysis, these correlated techniques provide standardized nomenclature and methodology for interpreting complex material interfaces across diverse fields including energy storage, biomedical devices, pharmaceuticals, and catalysis. This application note details experimental protocols, analytical workflows, and practical implementations for successfully bridging these powerful characterization modalities.

According to ISO 18115-1, surface analysis techniques probe the outermost atomic layers of materials to determine composition, chemical states, and molecular structure. No single technique provides complete information; rather, complementary approaches must be correlated to establish comprehensive material understanding. Scanning probe microscopy techniques offer exceptional topographical resolution but limited chemical specificity, while surface spectroscopy provides detailed chemical information but often with poorer spatial resolution [21].

Multimodal chemical imaging simultaneously offers high-resolution chemical and physical information with nanoscale and, in select cases, atomic resolution. By coupling modalities that collect physical and chemical information, researchers can address scientific problems in biological systems, battery and fuel cell research, catalysis, pharmaceuticals, and photovoltaics [21]. The combined systems enable local correlation of material properties with chemical makeup, making fundamental questions of how chemistry and structure drive functionality approachable.

This application note establishes standardized protocols within the ISO 18115-1 framework for correlating surface spectroscopy with scanning-probe microscopy, enabling researchers to obtain quantitatively reliable, reproducible data from these powerful multimodal platforms.

Technical Approaches & Instrumentation

Combined Scanning Probe Microscopy and X-Ray Spectroscopy

A versatile approach combines Shear Force Microscopy with X-Ray Spectroscopy to simultaneously obtain surface topography and chemical mapping. The instrument uses a sharp aluminum-coated optical fiber as a microscope probe to locally collect visible luminescence from samples under X-ray excitation [22]. This apparatus enables simultaneous pixel-by-pixel surface topography measurement and chemical mapping, working in ambient conditions or liquid environments.

Table 1: Technical Approaches for Correlating Surface Spectroscopy with SPM

Technique Combination	Spatial Resolution	Chemical Information	Primary Applications
AFM + IR Spectroscopy	~10 nm (IR)	Molecular vibrations, chemical bonds	Polymers, biological systems, organic semiconductors
AFM + Raman Spectroscopy (TERS)	<1 nm (Raman)	Molecular fingerprints, crystallinity	2D materials, catalysts, single molecule studies
Shear Force Microscopy + X-Ray Spectroscopy	~50-100 nm	Elemental composition, chemical states	Thin films, inorganic materials, ceramics
SNOM + Fluorescence	~20-50 nm	Electronic states, fluorophores	Nanophotonics, quantum dots, biological imaging

Infrared and Raman Spectroscopies with Scanning Probe Microscopy

Combining atomic force microscopy with optical spectroscopy overcomes diffraction limits in spatial mapping to obtain high-resolution local chemical maps. In tip-enhanced Raman scattering (TERS), the intrinsically low intensity of Raman scattering is successfully overcome with near-field amplification by the scanning probe [21]. Similarly, nanoscale infrared spectroscopy (nano-IR) enables chemical mapping based on infrared absorption with ~10 nm spatial resolution.

The adaptation of these approaches to microscopic platforms provides an avenue to map chemical signatures in a spatially resolved manner, overcoming intrinsic limitations of conventional instruments that average over an ensemble of molecular species [21]. These techniques provide information on chemical bonds and local chemical environments based on spectroscopic signatures recorded at specific spatial locations.

Experimental Protocols

Protocol: Combined Shear Force Microscopy and X-Ray Spectroscopy for Thin Film Analysis

Purpose: To simultaneously characterize surface topography and chemical composition of thin film samples using correlated shear force microscopy and X-ray spectroscopy.

Materials & Equipment:

• Home-made or commercial shear force microscope
• Synchrotron beam line or laboratory X-ray source
• Sharp aluminum-coated optical fiber probes (aperture ~50 nm)
• Thin film samples on appropriate substrates
• Vibration isolation system

Procedure:

• Sample Preparation:
  • Prepare thin films (~400 nm) by sputtering or other deposition methods onto silicon substrates.
  • Perform necessary annealing treatments (e.g., 900°C in air for ZnO films) to achieve desired crystallinity [22].
  • Mount samples in holder ensuring electrical grounding where appropriate.

• Instrument Setup:

  • Approach the optical fiber probe to the sample surface using shear force feedback until constant oscillation amplitude is maintained.
  • Align X-ray beam (synchrotron source) to illuminate sample precisely at the microscope probe apex.
  • Configure detection system to collect visible luminescence through the optical fiber probe.
  • Set scanning parameters: typically 1024 × 1024 pixels for adequate resolution, with scan speeds adjusted for signal quality.

• Data Acquisition:

  • Simultaneously record surface topography and X-ray excited optical luminescence (XEOL) pixel-by-pixel.
  • For XAFS-XEOL spectroscopy, scan X-ray energy through absorption edges of interest (e.g., Zn-K edge at 9664 eV) while monitoring luminescence intensity.
  • Acquire reference spectra from standard materials (e.g., stoichiometric ZnO powder) for calibration.
  • Maintain constant experimental conditions throughout acquisition, which may require 8+ hours for complete data sets [22].

• Data Processing:

  • Reconstruct topography images from shear force feedback signals.
  • Generate chemical maps from luminescence intensity at specific energies.
  • Perform image arithmetic (e.g., subtraction of pre-edge from post-edge images) to isolate element-specific signals.
  • Apply logical operations to identify regions rich in specific compounds [22].

Troubleshooting:

• Poor topographic resolution: Check probe sharpness and replace if worn.
• Weak luminescence signal: Optimize X-ray beam alignment; verify sample luminescence properties.
• Spatial drift during long acquisitions: Ensure thermal and vibrational stability; implement drift correction algorithms.

Protocol: Tip-Enhanced Raman Spectroscopy (TERS) for Nanoscale Chemical Mapping

Purpose: To obtain correlated topographical and chemical information with spatial resolution below 10 nm using TERS.

Materials & Equipment:

• Atomic force microscope with TERS capability
• Metal-coated AFM tips (Au or Ag) with sharp apex (<20 nm)
• Raman laser source (typically 532 nm, 633 nm, or 785 nm)
• High-sensitivity spectrometer with CCD detector
• Vibration isolation and environmental control system

Procedure:

• Tip Preparation:
  • Use commercially available TERS probes or fabricate by thermal evaporation of 20-50 nm Au or Ag coatings onto standard AFM tips.
  • Verify tip quality and plasmonic resonance using test samples.

• Sample Preparation:

  • Deposit samples on atomically flat substrates (mica, Au(111), or silicon wafer).
  • Ensure low sample roughness for optimal tip-sample interaction.
  • For biological samples, use appropriate fixation methods while preserving chemical integrity.

• Alignment and Optimization:

  • Approach tip to sample surface using standard AFM procedures.
  • Align laser focus to tip apex using confocal optics.
  • Optimize polarization for maximum field enhancement.
  • Verify enhancement using standard samples (e.g., carbon nanotubes, graphene).

• Data Acquisition:

  • Acquire topography images in tapping or contact mode.
  • Simultaneously collect Raman spectra at each pixel with integration times of 10-1000 ms.
  • Map specific Raman peaks to visualize chemical distribution.
  • Correlate topographical features with chemical maps.

• Data Analysis:

  • Process Raman spectra: subtract background, remove cosmic rays, normalize if required.
  • Generate chemical maps by integrating intensity of specific Raman bands.
  • Correlate chemical maps with topographical features.
  • Perform multivariate analysis for complex chemical systems.

Visualization & Data Analysis

Workflow for Multimodal Data Correlation

The following diagram illustrates the integrated workflow for correlating surface spectroscopy with scanning-probe microscopy:

Workflow for Multimodal Data Correlation

Data Co-Registration and Analysis

For multimodal imaging where data sets A(x,y) and B(x',y') are obtained from the same spatial region, the primary task becomes co-registration between spatial grids, potentially augmented by interpolation to extrapolate data to a single spatial grid yielding a compound object A,B [21]. Once such data are available, fundamentally different opportunities to explore and derive knowledge from material data emerge.

Advanced data analysis approaches include:

• Linear Unmixing: When signals are linear combinations of component spectra, classical linear unmixing methods with known or unknown end-members are applicable [21].
• Multivariate Analysis: Principal component analysis (PCA) and cluster analysis for identifying chemical phases and distributions.
• Machine Learning: Pattern recognition and classification algorithms for identifying relationships between topography and chemistry.

The Scientist's Toolkit: Research Reagent Solutions

Table 2: Essential Materials for Correlated Spectroscopy-SPM Experiments

Item	Function	Application Notes
AFM-TERS Probes	Plasmonic enhancement of Raman signals	Au-coated for visible/NIR, Ag-coated for enhanced efficiency but lower stability
Shear Force Probes	Topography and light collection	Aluminum-coated optical fiber with ~50 nm aperture [22]
Calibration Samples	Instrument validation	ZnO thin films, Si gratings, supported lipid bilayers
Reference Materials	Signal calibration	Stoichiometric ZnO powder, polystyrene beads, graphene
Vibration Isolation	Mechanical stability	Active or passive isolation systems for nm-scale resolution
Standard Substrates	Sample support	Si wafers, mica, Au(111), ITO-coated glass

Applications and Case Studies

Thin Film Semiconductor Analysis

The characterization of ZnO and ZnWO₄-ZnO thin layers demonstrates the power of combined shear force microscopy and X-ray spectroscopy. Simultaneous recording of topography and luminescence cartography at various incident energies revealed grains of 0.5 to more than 1μm, confirmed by conventional Atomic Force Microscopy [22]. By acquiring images before and after elemental absorption edges (Zn-K edge, W-L edge), researchers could distinguish ZnO-rich and ZnWO₄-rich regions through image arithmetic and logical operations.

Nanoscale Chemical Mapping of Materials

Combined infrared vibrational scattering scanning near-field optical microscopy (IR s-SNOM) with force-distance spectroscopy enables simultaneous characterization of both nanoscale optical and nanomechanical molecular properties [21]. This approach allows adhesion and elastic modulus to be overlaid with chemical maps, highlighting interplay between crystallinity, composition, and intermolecular interactions between and within single domains.

The correlation of surface spectroscopy with scanning-probe microscopy represents a powerful paradigm in materials characterization, enabling researchers to bridge the gap between nanoscale structure and chemical functionality. Standardized protocols within the ISO 18115-1 framework ensure reproducible, quantitatively reliable data across laboratories and instrument platforms. As these multimodal approaches continue to evolve, they will undoubtedly unlock new insights into complex materials systems across scientific disciplines, from energy storage and conversion to biomedical applications and beyond.

Avoiding Common Pitfalls: Strategies for Effective Implementation of Standard Terminology

In surface spectroscopy research, precise terminology is not merely a formality but a fundamental component of data integrity and scientific reproducibility. Terminology misuse introduces significant risks, including misinterpreted data, flawed experimental conclusions, and an inability to compare results across different laboratories and studies effectively. The ISO 18115-1 standard provides a critical framework, establishing agreed-upon definitions for general terms used in surface chemical analysis spectroscopies such as X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and secondary ion mass spectrometry (SIMS) [3] [23]. This Application Note, framed within the context of a broader thesis on ISO 18115-1, outlines frequent terminology errors encountered in research and drug development and provides actionable protocols for their correction.

Frequent Terminology Errors and Their Impact

Misused terms can propagate through the data analysis pipeline, leading to systematic errors in reporting and interpretation. The following table summarizes some of the most common categories of terminology errors.

Table 1: Common Terminology Errors and Their Consequences in Surface Spectroscopy

Error Category	Common Example of Misuse	ISO 18115-1 Preferred Term or Definition	Impact of Misuse
General Instrumentation	Using "component" to describe a spectral feature	The term "component" is deprecated for spectral features; use "peak" or "spectral feature" [24].	Imprecise communication and ambiguity in describing spectral fitting outcomes.
Peak Fitting & Backgrounds	Referring to a generic background subtraction as a "Shirley background"	Shirley background: A specific, non-linear background subtraction method defined by its particular shape and application [24].	Applying an incorrect background model leads to inaccurate peak areas and quantitative results.
Quantification & Sensitivity	Confusing "backscattering factor" with "backscattering coefficient"	Backscattering factor (deprecated): The preferred term is backscattering correction factor [24]. Backscattering coefficient has a distinct definition [24].	Incorrect quantitative analysis due to the application of wrong physical models in data processing.
Charge Referencing	Inconsistent use of "charge compensation," "charge neutralization," and "charge referencing"	Charge neutralization: The process of countering surface charge. Charge referencing: The process of calibrating the energy scale to a known reference peak (e.g., adventitious carbon) [24].	Misaligned binding energy scales, making cross-study comparisons invalid and introducing systematic shifts in reported chemical states.
Data Processing	Using "centring" instead of "centering"	The deprecated term "centring" is corrected to centering [24].	While seemingly minor, such inconsistencies hinder literature searches and can reflect a lack of attention to standardized methodology.

Experimental Protocols for Terminology-Compliant Analysis

Adhering to standardized protocols ensures that terminology is applied correctly throughout the experimental workflow, from data collection to publication.

Protocol: Pre-Measurement Instrument Calibration and Verification

Objective: To ensure the spectrometer is calibrated and functioning correctly, providing a valid foundation for data collection and subsequent analysis [25].

• Wavelength/Wavenumber Calibration:

  • Procedure: Regularly measure a certified wavelength/wavenumber standard (e.g., 4-acetamidophenol for Raman spectroscopy [25] or emission lines for spectrophotometers [26]).
  • Data Analysis: Use the measured peaks to construct a new, accurate wavenumber axis for your instrument. Interpolate all sample data to this common, fixed axis.
  • Terminology Compliance: Report the process as "wavelength/wavenumber calibration" using the defined terms from ISO 18115-1 for instrumental parameters [1] [23].

• Intensity/Photometric Linearity Check:

  • Procedure: Use a set of calibrated neutral density filters or other photometric standards to verify the linearity of the detector response across the intended measurement range [26] [27].
  • Data Analysis: Plot measured signal against expected transmittance or absorbance. Non-linearity indicates a need for instrumental correction or service.
  • Terminology Compliance: Distinguish correctly between "transmittance," "absorbance," and "photometric linearity" [26].

Protocol: Correct Data Processing and Peak Fitting Workflow

Objective: To standardize the data analysis pipeline, avoiding over-optimization and ensuring the correct application of background subtraction and peak fitting terminology [25] [28].

• Order of Operations:

  • Procedure: Adhere to a strict sequence: Cosmic spike removal → Wavelength/Intensity calibration → Baseline/Background correction → Spectral normalization → Denoising [25].
  • Terminology Compliance: Note that "background correction" in optical spectroscopy is analogous to "inelastic background subtraction" in electron spectroscopy. The specific method (e.g., Shirley, Tougaard) must be correctly identified and named [24].

• Peak Fitting Procedure:

  • Procedure: After a valid background subtraction, fit the spectral peaks using the minimum number of components justified by the chemical state information. Constrain fit parameters based on physically realistic values (e.g., spin-orbit splitting, branching ratios).
  • Terminology Compliance: Refer to individual spectral features as "peaks" or "components." Report the "peak area" and "binding energy" correctly, stating the charge referencing method used (e.g., "adventitious carbon referencing") [24].

Protocol: Rigorous Model Evaluation and Statistical Reporting

Objective: To prevent overestimation of model performance and ensure statistical conclusions are reliable and terminology is correct [25].

• Independent Validation:

  • Procedure: Partition data such that all measurements from a single biological replicate or patient sample are contained entirely within the training, validation, or test set (replicate-out cross-validation).
  • Terminology Compliance: Clearly report the validation method used, distinguishing between "cross-validation" and "replicate-out cross-validation" to prevent "model evaluation errors" [25].

• Statistical Testing:

  • Procedure: When comparing multiple Raman band intensities, apply a correction for multiple testing (e.g., Bonferroni correction). Use non-parametric tests (e.g., Mann-Whitney-Wilcoxon U test) if the data does not meet the assumptions of parametric tests like the t-test.
  • Terminology Compliance: Report the specific statistical test used and the applied corrections to avoid "p-value hacking" [25].

The Scientist's Toolkit: Essential Research Reagents and Materials

The following table lists key materials and reagents required for conducting accurate and terminology-compliant surface spectroscopy experiments.

Table 2: Essential Research Reagents and Materials for Surface Spectroscopy

Item	Function/Brief Explanation	Relevant ISO 18115-1 Terminology
Certified Wavelength/Wavenumber Standard	Calibrates the wavelength/wavenumber axis of the spectrometer to ensure spectral accuracy [25].	Certified Reference Material (CRM): A reference material characterized by a metrologically valid procedure [24].
Charge Referencing Standard	Provides a known spectral peak for calibrating the binding energy scale in XPS (e.g., Adventitious Carbon, Au 4f).	Adventitious carbon referencing: A specific charge referencing procedure [24]. Charge referencing is the general process [24].
Certified Photometric Standard	Verifies the photometric linearity and intensity response of the spectrometer (e.g., neutral density filters) [26] [27].	Related to ensuring photometric linearity and correct transmittance/absorbance values [26].
Sputtered Depth Profiling Standard	A sample with a known, certified thin-film structure used to calibrate depth resolution in techniques like XPS and AES.	Used for establishing a compositional depth profile [24].
Pure Element or Compound Standards	Used for establishing relative sensitivity factors (RSFs) for quantitative analysis.	Absolute elemental sensitivity factor and average matrix relative sensitivity factor are key terms for quantification [24].

The consistent and correct application of terminology as defined by ISO 18115-1 is a cornerstone of rigorous and reproducible surface spectroscopy research. By integrating the protocols and corrective measures outlined in this document, researchers and drug development professionals can significantly reduce systematic errors stemming from terminology misuse. This practice enhances the clarity, reliability, and collaborative potential of scientific data, ensuring that findings are accurately communicated and can be confidently built upon by the broader scientific community.

The adoption of standardized terminology, as defined in ISO 18115-1, is critical for ensuring clarity, reproducibility, and effective communication in surface spectroscopy research [29]. This document provides a practical framework for integrating the vocabulary and principles of this standard into daily laboratory practice. It outlines a structured training protocol and details the necessary resource allocation, serving as a guide for research teams and laboratory managers in pharmaceuticals and materials science. The consistent application of these standards minimizes analytical ambiguity, facilitates data comparison across studies and institutions, and enhances the reliability of research outcomes in fields such as drug development and biomaterials engineering [30] [29].

Background and Rationale

Surface analysis techniques, particularly X-ray Photoelectron Spectroscopy (XPS), are indispensable in advanced research and development. They provide critical quantitative elemental and chemical state information from the top few nanometers of a sample, which is vital for understanding material interactions, coating efficacy, and device performance [30]. However, the power of these techniques is diminished without a unified language. ISO 18115-1 establishes this unified vocabulary, covering general terms and terms used in spectroscopy, thereby providing a common ground for scientists [29].

Inconsistent use of terminology can lead to misinterpretation of data, inability to replicate experiments, and errors in regulatory submissions. For instance, confusion in terms describing spectral features or data analysis procedures can compromise the integrity of a research report. Adopting ISO 18115-1 mitigates these risks by providing a definitive reference. This application note bridges the gap between the formal standard and its day-to-day implementation, ensuring that the theoretical benefits of standardization are realized in practical laboratory operations [29].

Experimental Protocol for Standard Implementation

This protocol provides a step-by-step methodology for integrating ISO 18115-1 into a research organization's daily workflow, from initial assessment to full implementation and ongoing review.

Materials and Reagents

• ISO 18115-1:2023 Document: The core reference standard, "Surface chemical analysis - Vocabulary - Part 1: General terms and terms used in spectroscopy" [29].
• Internal Documentation: Existing Standard Operating Procedures (SOPs), method descriptions, and data reporting templates.
• Training Materials: Slide decks, quick-reference guides, and example datasets tailored to the organization's research focus (e.g., biomaterials, metal oxides) [30].

Equipment

• Computers with Internet Access: For accessing digital copies of the standard and online training modules.
• Presentation Equipment: For hosting in-person or virtual training workshops.
• Laboratory Information Management System (LIMS) or Data Repository: For storing and sharing standardized data and reports.

Procedure

• Gap Analysis and Baseline Assessment

  • Critical Step: Convene a team of lead scientists and technicians to review the ISO 18115-1 document [29].
  • Systematically audit a sample of current internal documents, including SOPs, recent reports, and data archives, to identify terminology that deviates from the standard.
  • Create a master list of non-conforming terms and their ISO-standardized equivalents. Example: Replace internal jargon for spectral artifacts with the correct ISO term.

• Development of Training Resources

  • Develop a structured training curriculum based on the gap analysis. The curriculum should be role-specific, with basic training for all lab personnel and advanced modules for data analysts and report authors.
  • Create a "Terminology Handbook" that summarizes the most critical ISO terms and their definitions, using practical examples from the organization's field of work (e.g., applying terms to XPS depth profiling of polymers) [30].
  • Pause Point: Training materials can be drafted and reviewed by a quality assurance team before rollout.

• Phased Training and Implementation

  • Roll out training sessions in phases, starting with a pilot group from one project team.
  • In workshops, use real, de-identified data from the organization. Have participants practice by re-writing old method descriptions or annotating spectra using the new standardized terminology [31].
  • Integrate terminology checks into the existing data review and report approval workflows. A senior scientist should verify compliance with ISO 18115-1 before final sign-off.

• Integration into Quality Systems

  • Officially revise all relevant SOPs, method files, and report templates to align with ISO 18115-1 terminology.
  • Update the controls in the LIMS or data management system to include mandatory fields for standardized terms where appropriate.
  • Caution: Ensure that all changes are version-controlled and communicated to the entire team to maintain consistency.

• Validation and Continuous Improvement

  • Validation of Protocol: After a 3-month implementation period, conduct a follow-up audit of new reports and data entries to measure adherence to the standard.
  • Solicit feedback from researchers on the clarity and utility of the new terminology via anonymous surveys.
  • Schedule annual reviews of the implementation protocol to incorporate updates to the ISO standard and address emerging challenges.

Data Analysis

The success of the implementation should be measured using both quantitative and qualitative metrics. Quantitatively, track the percentage of audited reports that achieve full terminology compliance. Qualitatively, analyze survey feedback to gauge user confidence and perceived improvements in communication and data reproducibility [31].

Successful integration of ISO 18115-1 requires a combination of foundational documents, practical tools, and human resources. The following table details these key components.

Table 1: Key Research Reagent Solutions for Standards Implementation

Item Category	Specific Item/Resource	Function & Application in Implementation
Core Reference Material	ISO 18115-1:2023 Standard Document [29]	Provides the definitive definitions for general terms and spectroscopic terms, serving as the primary authority for all terminology disputes and decisions.
Training Aid	Curated XPS Application Webinars [30]	Offers practical, field-specific examples (e.g., polymer analysis, bio-surfaces) that demonstrate the application of standard concepts and terminology in real-world research.
Data Management Tool	Laboratory Information Management System (LIMS)	The platform for enforcing terminology use; standardized terms can be embedded as mandatory fields in data entry forms, ensuring consistency across projects.
Quality Control Asset	Internal Audit Checklist	A tool for periodically assessing compliance. It verifies that reports, SOPs, and data annotations consistently use the correct terminology as defined by the standard.
Expert Resource	Designated Standards Champion	A senior scientist tasked with providing guidance, resolving terminology questions, and leading the ongoing development of training materials and protocols.

Mandatory Visualizations

Workflow for Standards Implementation

The following diagram visualizes the end-to-end process for integrating ISO 18115-1 into daily laboratory practice, from initial planning to sustained use.

Data Management and Reporting Pathway

This diagram details the specific data lifecycle, highlighting checkpoints where standardized terminology must be applied to ensure consistency from acquisition to final reporting.

Validation of Protocol

The efficacy of this implementation protocol is validated by its structured approach, which mirrors established practices for methodological rigor and clarity in scientific research [31] [32]. The step-by-step procedure, complete with critical checkpoints and a defined validation phase, ensures that the integration of ISO 18115-1 is not merely theoretical but actively embedded into the research workflow. The use of practical tools like curated webinars [30] and the structured resource table ensures that researchers can connect standardized terms directly to their analytical work. The final validation audit and feedback mechanism provide concrete, measurable evidence of the protocol's success in achieving terminology compliance and enhancing report quality.

General Notes and Troubleshooting

• Note on Applicability: While this protocol is framed within surface spectroscopy, its structure is adaptable for implementing other technical standards across various scientific disciplines.
• Troubleshooting - Resistance to Change: If researchers are resistant to adopting new terminology, reinforce training with case studies showing how standard terms prevent errors and improve collaboration.
• Troubleshooting - Complex Terminology: For terms that are difficult to apply, create a living "FAQ and Examples" document where scientists can contribute questions and consensus answers, curated by the Standards Champion.
• Limitation: This protocol requires dedicated time and personnel resources for initial setup and training. Full benefits are realized only after the complete integration into the quality management system.

In surface spectroscopy research, documentation serves the critical dual purpose of ensuring reproducibility and regulatory compliance, without succumbing to unnecessary verbosity. The broader framework of ISO 18115-1, which establishes general terms for surface chemical analysis, emphasizes standardized reporting to facilitate clear communication and data exchange within the scientific community. For researchers, scientists, and drug development professionals, the challenge lies in determining what constitutes essential information versus superfluous detail. This balance is particularly crucial in regulated environments where compliance is mandatory, yet efficiency is valued.

Recent studies highlight a significant reproducibility crisis in scientific research, partly attributable to insufficient methodological detail in publications [6]. Surface analysis techniques like X-ray photoelectron spectroscopy (XPS) are particularly vulnerable to documentation shortcomings, as inexperienced users may overlook critical parameters essential for replicating experiments [6]. This application note provides structured protocols and frameworks designed to help researchers maintain this critical balance, ensuring comprehensive yet concise documentation that satisfies both scientific and regulatory requirements.

Core Principles for Efficient Documentation

The Essential Information Framework

Effective documentation must satisfy two overarching principles: enabling independent reproduction of experiments and providing all necessary data to support reported conclusions. The FAIR Data Principles (Findable, Accessible, Interoperable, and Reusable) provide a valuable framework for achieving these goals [33]. Adherence to these principles ensures that data retains its value over time and across different research contexts.

Specific essential elements include:

• Complete experimental conditions sufficient for replication
• Appropriate controls and validation data
• Clear sample preparation and handling protocols
• Instrument parameters and calibration data
• Data processing methods with justification for any manipulations

Conversely, excessive detail often manifests as:

• Repetitive methodological descriptions for standard techniques
• Inclusion of raw data that does not directly support conclusions
• Overly verbose explanations of established concepts
• Unnecessary procedural minutiae that do not impact outcomes

Strategic Omission Without Compromise

Strategic omission of certain information represents a key aspect of streamlined documentation. According to established guidelines, researchers can safely exclude:

• Standard techniques and methods that are well-established in the field, with appropriate citations to authoritative protocols [34]
• Descriptions of widely available commercial instruments identified by model or stock numbers unless the specific instrument characteristics directly impact results [34]
• Routine sample preparation steps that follow common laboratory practices, unless deviations from standard protocols occur

The Royal Society of Chemistry guidelines explicitly state: "Standard techniques and methods used throughout the work should be stated at the beginning of the experimental section; descriptions of these are not needed" [34]. This principle of referencing established methods rather than reproducing them in full represents a cornerstone of efficient scientific documentation.

Surface Spectroscopy Application Protocols

X-Ray Photoelectron Spectroscopy (XPS) Reporting Framework

XPS requires careful documentation to ensure data reproducibility and validity. The following protocol outlines essential reporting elements while avoiding common documentation pitfalls.

Table 1: Essential vs. Excessive Documentation in XPS Reporting

Essential Elements	Excessive Details to Omit	Rationale
Instrument calibration status and reference materials used	Basic operating principles of XPS	Standard theory can be referenced; focus on application-specific parameters
Charge correction method and reference peaks	Step-by-step software operation	Assume user competence with standard software interfaces
Sample preparation history and handling conditions	Routine maintenance procedures	Unless maintenance directly impacts specific results
X-ray source parameters and analyzer settings	All raw data without curation	Include only representative data supporting conclusions
Data processing methods with justification for each step	Repetitive methodological descriptions	Reference established methods rather than reproducing them

For XPS reporting, the essential information falls into several critical categories. Instrument conditions must include the specific instrument model, X-ray source characteristics (anode material, power), analyzer pass energy, and step size for spectral acquisition. The calibration status should be verified and reported using recognized reference materials, with any deviations from standard protocols documented. Sample preparation details must encompass the complete history, including cleaning procedures, environmental exposure, and any pre-treatment steps. Data processing methods require transparent documentation, including peak-fitting parameters, background subtraction methods, and charge referencing approaches [6].

Multi-technique Surface Analysis Documentation

Many surface characterization projects employ complementary analytical techniques to obtain comprehensive material understanding. The documentation strategy for such multi-technique studies requires careful integration of essential information across methodologies while avoiding redundant descriptions of shared procedural aspects.

Table 2: Cross-Technique Documentation Standards for Surface Spectroscopy

Technique	Minimal Essential Parameters	Validation Requirements	Common Omissions
XPS	Charge reference method, pass energy, step size, dwell time, X-ray source specifications	Reference material analysis, calibration verification, peak-fitting statistics	Sample charging history, charge neutralizer settings, spectral summation count
IR Spectroscopy	Resolution, number of scans, aperture setting, detector type, crystal material (for ATR)	Background spectrum frequency, ambient conditions, solvent subtraction details	Basic optical principles, alignment procedures, purge cycle details
Raman Spectroscopy	Laser wavelength and power, grating, objective magnification, integration time	Laser frequency calibration, spatial resolution verification, fluorescence mitigation	Standard filter descriptions, basic scattering theory, laser safety protocols
AFM/SPM	Scan mode, tip characteristics, setpoints, feedback parameters, scan rate	Scanner calibration, resolution verification, vibration isolation method	Standard cantilever properties, basic operational theory, routine alignment steps

The integration of multiple techniques necessitates special documentation considerations. Cross-technique correlations should be clearly articulated, with any discrepancies between methods acknowledged and explained. Shared sample handling procedures can be documented once in a dedicated section rather than repeated for each technique. Temporal relationships between measurements should be indicated when the sequence of analyses might impact results. Most importantly, technique-specific limitations must be acknowledged, with appropriate caveats regarding interpretation of complementary data sets [33] [6].

Structured Data Presentation Standards

Tabular Data Summarization

Well-structured tables represent one of the most effective tools for presenting complex experimental data concisely. Tables should include all necessary information for independent evaluation of results while excluding redundant or derivable data.

Table 3: Compound Characterization Data Reporting Standards

Compound ID	Yield (%)	Melting Point (°C)	NMR Data (δ, solvent)	Mass Spec Data (m/z)	Elemental Analysis (Found/Required)
7a	56	157 (from CHCl₃)	δH(400 MHz; CDCl₃) 2.3 (3H, s), 7.3-7.6 (5H, m)	183 (M⁺, 41%), 168 (38)	C, 63.1; H, 5.4 / C, 63.2; H, 5.3
7b	72	202-204 (from EtOH)	δH(400 MHz; DMSO) 3.16 (3H, s), 7.8 (1H, br s)	247 (M⁺, 100%), 232 (15)	C, 58.1; H, 4.9 / C, 58.3; H, 4.8
9c	63	189-191 (dec)	δC(100 MHz; CDCl₃) 172.5 (CO), 140.2 (ArC)	352 (M⁺, 25%), 337 (42)	C, 65.3; H, 5.8 / C, 65.5; H, 5.7

For biological applications, additional characterization requirements apply. Antibody reagents must be documented with host species, clonality (monoclonal/polyclonal), commercial source (including catalog and lot numbers), and application-specific validation [33]. Cell lines require authentication method and date, mycoplasma testing status, and source information. Experimental organisms need detailed descriptions including source, species, strain, sex, age, and housing conditions, following the ARRIVE guidelines for in vivo studies [33].

Spectroscopic Data Reporting Workflow

The documentation of spectroscopic data follows a logical progression from raw data acquisition through processing to interpretation. The following workflow ensures comprehensive reporting while maintaining focus on essential information.

The Scientist's Toolkit: Essential Research Reagents and Materials

Table 4: Essential Research Reagents and Reference Materials for Surface Spectroscopy

Reagent/Material	Function	Documentation Requirements	Quality Control
Charge Reference Standards	Energy scale calibration for XPS	Source, purity, observed binding energies, storage conditions	Periodic verification against certified values
Sputter Depth Profiling Standards	Depth scale calibration for ion beam techniques	Composition, structure, reference depth values	Cross-validation with profilometry measurements
Reference Catalysts	Method validation for catalytic studies	Source, composition, expected performance metrics	Periodic activity testing against certification data
Surface Roughness Standards	Topographical reference for SPM/AFM	Certified roughness values, material composition	Verification of calibration transfer
Antibody Validation Panels	Specificity confirmation for biological studies	Host species, clonality, target epitopes, applications	Regular functionality testing with positive/negative controls

Compliance and Repository Deposition Framework

Data Repository Selection and Utilization

Adherence to data sharing policies represents a critical aspect of modern scientific compliance. The ACS strongly encourages authors to deposit data in discipline-specific, community-recognized repositories that issue persistent unique identifiers such as DOIs or accession numbers [33]. This practice enhances data findability, accessibility, interoperability, and reusability—the core principles of the FAIR framework.

Repository selection should follow a logical decision process based on data type and domain standards. Resources such as re3data.org and FAIRsharing.org provide curated information on available repositories, their certification status, and services offered [33]. For specialized data types, domain-specific repositories often provide optimal discovery and preservation capabilities.

Minimum Reporting Requirements Checklist

The following checklist provides a verification tool for ensuring comprehensive yet concise documentation:

• Sample Information: Complete provenance, preparation history, and storage conditions
• Instrument Specifications: Model, calibration status, and critical acquisition parameters
• Experimental Conditions: Environment, measurement settings, and replication details
• Data Processing Methods: Transparent description with justification for each step
• Reference Materials: Documentation of standards used for calibration/validation
• Repository Deposits: Persistent identifiers for raw and processed data
• Compliance Statements: Ethical approvals, data policy acknowledgments

This framework ensures that surface spectroscopy research meets the dual demands of scientific rigor and regulatory compliance while avoiding the documentation bloat that can obscure meaningful findings. By focusing on essential information and employing structured presentation formats, researchers can communicate their work effectively while supporting reproducibility and scientific progress.

For research organizations engaged in surface spectroscopy, the adoption of a standardized vocabulary as outlined in ISO 18115-1 is not merely an administrative task but a critical strategic initiative. These Application Notes and Protocols provide a structured framework for researchers, scientists, and drug development professionals to effectively communicate the operational, scientific, and financial value of this standardization to organizational leadership. The core challenge lies in translating a technical standard into a compelling business case that resonates with leaders focused on research efficacy, data integrity, and resource optimization. Success hinges on demonstrating a clear link between standardized terminology and tangible outcomes such as accelerated discovery timelines, enhanced cross-functional collaboration, and improved data reproducibility [31].

The Strategic Rationale for Standardized Vocabulary

Quantitative Benefits of Standardization

A primary driver for leadership buy-in is the demonstrable impact on research efficiency and data quality. The following table summarizes the core quantitative and qualitative benefits that directly address typical leadership concerns.

Table 1: Benefits of Implementing ISO 18115-1 Standardized Vocabulary

Benefit Area	Impact on Research Operations	Leadership Value
Data Integrity & Reproducibility	Eliminates ambiguity in spectral data interpretation and reporting [31].	Reduces costly replication studies and strengthens regulatory submissions.
Collaboration Efficiency	Creates a shared language across teams, disciplines, and geographic locations [35].	Accelerates project timelines and optimizes use of distributed talent.
Knowledge Transfer	Simplifies onboarding of new researchers and preserves institutional knowledge [36].	Lowers training costs and mitigates risk associated with staff turnover.
Data Interoperability	Enables seamless data merging and comparative analysis from different instruments and legacy studies.	Unlocks the full potential of data mining and AI-driven discovery.
Publication & Peer Review	Minimizes errors in data presentation, facilitating smoother publication and peer recognition [31].	Enhances organizational reputation and credibility in the scientific community.

The Communication Imperative

Leaders must understand that poor communication, including inconsistent terminology, directly derails focus and misaligns teams [35]. Effective leadership communication is a philosophy that guides how a vision, such as standardization, is delivered and perceived. It transcends mere words, encompassing non-verbal cues, active listening, and strategic channel selection to ensure the message is not just heard but understood and adopted [35]. When proposing a significant change like vocabulary standardization, leaders are advised to avoid overly complex language and jargon, which can create confusion, suspicion, and alienation [37]. Instead, the vision must be clear, compelling, and straightforward to communicate and receive.

Protocol for Demonstrating Value and Securing Buy-In

This protocol outlines a step-by-step methodology for building a compelling, evidence-based case for adopting ISO 18115-1.

Phase 1: Internal Assessment and Baseline Establishment

• Objective: Quantify the current-state costs of non-standardization.
• Methods:
  • Process Mapping: Document the workflow for a common analysis, from data acquisition to publication-ready figure. Identify steps where terminology ambiguity causes delays, rework, or errors.
  • Error Log Analysis: Review laboratory notebooks and quality control records over the preceding 6-12 months to categorize errors linked to miscommunication or unclear terminology.
  • Structured Interviews: Conduct brief, anonymous interviews with researchers from different career stages (e.g., PhD students, post-docs, principal investigators) to gather qualitative data on time lost clarifying terms or reconciling data sets.

Phase 2: Develop a Compelling Value Proposition

• Objective: Synthesize assessment data into a leadership-focused narrative.
• Methods:
  • Calculate Cost of Inaction: Project the time and financial costs of continuing without a standard, using baseline data (e.g., total person-hours spent monthly on clarifying terminology).
  • Benchmarking: If available, reference published case studies or white papers from analogous fields that realized efficiency gains post-standardization.
  • Craft a Visionary Message: Frame the adoption of ISO 18115-1 not as a compliance exercise, but as a strategic enabler. Use a metaphor, such as "transitioning from a tower of Babel to a unified symphony of data," to create a memorable picture of the future state [37]. A visionary leader mobilizes people by "painting compelling pictures of future success" [38].

Phase 3: Tailored Communication and Engagement

• Objective: Present the case to leadership using adaptive communication styles.
• Methods:
  • Identify Leadership Styles: Adapt your communication strategy based on the dominant styles within the leadership team [38].
  • Execute the Plan:
    • For Visionary Leaders: Emphasize the long-term strategic advantage and how standardization positions the organization as a pioneer.
    • For Democratic Leaders: Present the collected data from the team and seek their input on the implementation pathway.
    • For Directive Leaders: Focus on the clear, actionable steps, timelines, and expected ROI, using the data from Phase 1 to justify the decision.

Table 2: Adaptive Communication Strategies for Leadership Engagement

Leadership Style [38]	Recommended Communication Approach	Key Messaging Focus
Visionary	Inspire with the future possibility.	"This standard positions us as industry pioneers by unlocking AI-driven discovery."
Democratic	Facilitate input and build consensus.	"Based on team feedback, here are the observed challenges and a proposed path forward."
Directive	Provide clear, data-backed actions.	"The data shows a 15% efficiency loss. Here is the mandated standard and rollout plan."
Coaching	Guide leaders to discover the value.	"How might improved data clarity impact our project success rates and grant funding?"

The following workflow diagrams the complete protocol from assessment to full implementation, providing a visual summary of the process.

Diagram 1: Buy-In and Implementation Workflow

Successful implementation requires more than a document; it demands a suite of practical resources. The following table details the key components of an effective implementation toolkit.

Table 3: Research Reagent Solutions for Vocabulary Standardization

Tool Name	Function	Target User Group
ISO 18115-1 Quick Reference Guide	A simplified, searchable digest of core terms and definitions specific to the organization's common techniques.	All research staff, especially new hires and students.
Annotated Data Template Library	Standardized digital templates for reporting spectral data (e.g., XPS, AES) with pre-populated, compliant terminology fields.	Researchers compiling data for internal reports or publications.
Electronic Lab Notebook (ELN) Plug-in	Integrates the standard vocabulary directly into the data entry workflow, suggesting compliant terms as researchers type.	All wet-lab and computational researchers.
Training Modules & Case Studies	Interactive, scenario-based training that illustrates the cost of non-standardization and the benefits of compliance.	All staff, with specialized versions for leadership and new employees.
Manager Communication Toolkit [36]	A curated set of resources (FAQs, talking points, presentation slides) that helps team leaders explain the "why" behind the standard to their reports.	Principal Investigators, Project Managers, and Team Leads.

Sustaining Leadership Engagement

Securing initial buy-in is only the first step. Long-term success requires continuous reinforcement. Leaders must repeat important messages far more often than they intuitively feel is necessary, as people need to hear a message multiple times before they internalize and act on it [36]. Furthermore, leaders should stop and listen, creating consistent feedback channels such as "Ask Me Anything" sessions or anonymous surveys to gauge adoption, identify lingering friction points, and demonstrate that leadership is engaged and responsive to the team's experience [35] [36]. This continuous two-way communication loop ensures the standardized vocabulary remains a living, supported tool rather than a forgotten initiative.

Ensuring Data Integrity: How Standardized Terminology Validates and Compares Research

In the field of surface chemical analysis, where techniques like X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) provide critical data for material characterization and drug development, the consistent application of terminology forms the bedrock of scientific reproducibility. The International Standard ISO 18115-1:2023, titled "Surface chemical analysis — Vocabulary — Part 1: General terms and terms used in spectroscopy," addresses this fundamental need by establishing a unified linguistic framework that enables precise communication and data comparability across laboratories, research institutions, and industrial applications worldwide [1]. This document represents the third edition, published in June 2023, reflecting a significant evolution from the 2013 version with substantial additions and revisions that respond to emerging analytical techniques and community-identified needs [1] [5].

For researchers and drug development professionals, the standard provides the essential foundation for ensuring that experimental data, methodologies, and findings described in scientific literature, patents, and regulatory submissions are interpreted consistently by all stakeholders. By defining terms for samples, instruments, and analytical concepts with precision, ISO 18115-1:2023 facilitates the cross-disciplinary collaboration necessary for innovation in advanced materials and pharmaceutical development while supporting the data integrity requirements of regulatory frameworks.

Scope and Key Features of ISO 18115-1:2023

Comprehensive Coverage

ISO 18115-1:2023 provides standardized definitions for terminology used throughout surface chemical analysis, with specific focus on spectroscopic techniques. The document's 116 pages contain approximately 630 terms systematically organized to support researchers in locating related concepts efficiently [1] [5]. The standard is structured to complement ISO 18115-2, which covers terms used in scanning-probe microscopy, and ISO 18115-3, which addresses optical interface analysis, creating a comprehensive vocabulary ecosystem for the surface analysis community [1].

The terminology encompasses the entire experimental workflow, including:

• Sample preparation and characterization
• Instrumentation and measurement parameters
• Data acquisition and processing methodologies
• Analytical concepts and quantification approaches

Key Revisions and Additions

The 2023 revision introduces substantial updates to reflect technological advancements and evolving scientific practices in surface analysis. According to research by Shard, Baer, and Clifford (2024), this revision includes clarifications, modifications, or deletions to more than 70 terms and adds more than 50 new terms [5]. Significant expansions include:

• Technical advancements: Terminology for emerging methods such as atom probe tomography (APT), near ambient pressure XPS, and hard X-ray photoelectron spectroscopy [5]
• Resolution standardization: 25 new and revised terms to ensure consistent description of resolution across all surface analysis methods [5]
• Analytical techniques: Comprehensive coverage of terms used in AES, XPS, SIMS, glow discharge spectroscopy, X-ray reflectivity (XRR), ion scattering, and multivariate analysis [5]

Table 1: Quantitative Overview of ISO 18115-1:2023 Terminology

Category	Number of Terms	Key Additions in 2023 Revision
General Terms	~200	Sample terminology, measurement principles
Spectroscopy Terms	~430	Resolution concepts, emerging techniques
Resolution Terminology	25	Consistent descriptors across methods
New Techniques	>50	APT, near ambient pressure XPS, HAXPES
Revised/Clarified Terms	>70	Updated definitions reflecting current usage

Quantitative Data Analysis

The evolution of ISO 18115-1 reflects the dynamic nature of surface chemical analysis as a discipline. The expansion from approximately 900 terms across both Parts 1 and 2 in the 2013 version to the current focused revision demonstrates the standard's responsiveness to technological progress [5] [3]. The deliberate organization of terms into subject-specific sections addresses practical usability concerns, enabling researchers to efficiently locate related terminology during experimental design, data interpretation, and reporting phases [5].

Table 2: Comparative Analysis of ISO 18115-1 Revisions

Parameter	ISO 18115-1:2013	ISO 18115-1:2023	Change
Publication Date	2013	June 2023	10-year cycle
Total Pages	Not specified	116	-
Key Techniques Covered	AES, XPS, SIMS, GD	Adds APT, NAP-XPS, HAXPES	Significant expansion
Resolution Terms	Limited set	25 specialized terms	Major conceptual development
Accessibility	8 approved websites [3]	ISO portal & national bodies	Improved access

The quantitative expansion in terminology specifically addresses critical gaps identified by the surface analysis community, particularly regarding resolution metrics and emerging methodologies. This development supports more precise instrument characterization and enables more accurate cross-laboratory method transfer – an essential requirement for pharmaceutical applications where analytical results may influence regulatory decisions.

Experimental Protocols for Implementation

Protocol 1: Standard Terminology Implementation for Method Documentation

Purpose: To ensure consistent application of ISO 18115-1 terminology in experimental documentation for surface analysis studies.

Materials:

• ISO 18115-1:2023 reference document
• Laboratory standard operating procedure (SOP) template
• Analytical instrument data acquisition software

Procedure:

• Terminology Audit: Review existing method documentation against ISO 18115-1 definitions for key terms including "analysis area," "information depth," and "energy resolution" [5]
• Cross-reference Mapping: Create a laboratory-specific glossary linking instrument software terminology to corresponding ISO standard terms
• SOP Modification: Revise analytical method SOPs to incorporate standardized definitions for all critical measurement parameters
• Validation: Conduct parallel analysis using original and revised terminology to verify consistent interpretation across analysts
• Training: Implement training sessions focusing on proper application of revised terminology in data recording and reporting

Quality Control: Regular audit of laboratory records for terminology consistency; inclusion of terminology requirements in data review checkpoints

Protocol 2: Interlaboratory Comparison Using Standardized Terminology

Purpose: To validate measurement comparability across multiple laboratories using ISO 18115-1 terminology framework.

Materials:

• Reference materials with certified surface properties
• ISO 18115-1:2023 document
• Data reporting template with standardized terminology
• Statistical analysis software

Procedure:

• Study Design: Develop a round-robin testing protocol using defined reference materials
• Terminology Alignment: Conduct pre-study meeting to align all participants on application of relevant ISO terms including "lateral resolution," "analytical area," and "detection efficiency"
• Standardized Reporting: Implement unified data reporting template with mandatory use of standardized terms for all measured parameters
• Data Collection: Execute analytical measurements according to defined protocols across participating laboratories
• Statistical Analysis: Compare results using defined metrics with focus on terminology impact on data interpretation variance

Quality Control: Control charts for key measurement parameters; terminology compliance verification in data submissions

Workflow Visualization

The following diagram illustrates the systematic process for implementing ISO 18115-1 terminology in surface analysis research, ensuring data comparability and reproducibility:

The Scientist's Toolkit: Essential Research Reagent Solutions

Table 3: Key Research Materials and Resources for ISO 18115-1 Implementation

Resource Category	Specific Examples	Function in Research
Reference Standards	Certified reference materials with known surface composition	Validate analytical methods and instrument calibration using standardized terminology
Primary Standard Document	ISO 18115-1:2023 complete document [1]	Definitive reference for all terminology definitions and usage guidelines
Secondary Literature	Shard et al. (2024) review article [5]	Contextual understanding of key changes and implementation strategies
Access Platforms	National Physical Laboratory (UK), AIST (Japan) websites [3]	Access to standard documentation for educational purposes
Resolution Reference Materials	Certified nanostructured gratings, sharp edge samples	Quantify lateral resolution using standardized definitions [5]
Data Analysis Software	Multivariate analysis packages	Implement standardized data processing terminology [5]

ISO 18115-1:2023 represents a critical infrastructure component for advancing reproducibility in surface chemical analysis. By providing a precisely defined vocabulary that evolves with analytical technology, the standard addresses a fundamental requirement for scientific progress – the ability to build confidently upon previously reported findings. For researchers and drug development professionals, consistent implementation of this terminology framework reduces ambiguous interpretation, facilitates method transfer, and ultimately strengthens the evidential basis for technological innovations and regulatory decisions. The significant revisions in the 2023 edition, particularly for emerging techniques and resolution metrics, ensure the standard's continued relevance in an era of rapidly advancing analytical capabilities.

The reproducibility crisis in science underscores a critical need for standardized methodologies in analytical measurement, particularly in surface science where technique-specific jargon can create significant barriers to data correlation and interpretation [6]. For researchers using a suite of surface characterization techniques—X-ray Photoelectron Spectroscopy (XPS), Hard X-ray Photoelectron Spectroscopy (HAXPES), and Atom Probe Tomography (APT)—the challenge of integrating multidimensional data is substantial. This application note establishes a structured framework for cross-technique validation, firmly grounded in the terminology and principles of ISO 18115-1:2023, which defines terms for surface chemical analysis. Adherence to this standard is not merely procedural; it is fundamental to achieving reliable correlation between data from techniques with different information depths, dimensionalities, and physical bases. Such standardized correlation is especially critical in fields like drug development, where understanding surface composition and interfacial chemistry at the nanoscale directly impacts product performance and safety.

Core Technique Profiles and Comparative Metrics

A foundational step in cross-technique validation is a clear understanding of the fundamental operating parameters and capabilities of each technique, as defined by ISO 18115-1. The following table summarizes these key characteristics.

Table 1: Core Technique Profiles and Comparative Metrics Based on ISO 18115-1 Definitions

Parameter (ISO 18115-1 Term)	XPS	HAXPES	APT
Analyzed Volume	Top ~5-10 nm [39]	Top ~20-30 nm [40]	Tip-shaped specimen, ~100-250 nm in length
Lateral Resolution	≥ 10 μm (lab-based) [40]	≥ 10 μm (lab-based) [40]	Sub-nanometer
Depth Resolution	~1-3 nm (for Al Kα)	~2-5 nm (for Cr Kα) [40]	Atomic layer resolution (~0.3 nm)
Information Obtained	Elemental ID & concentration, chemical state [41] [6]	Elemental ID & concentration, chemical state (including buried interfaces) [40]	Elemental ID & isotopic composition, 3D spatial reconstruction
Primary Signal (ISO)	Photoelectrons	Photoelectrons	Ions (field-evaporated)
Destructive?	Essentially non-destructive	Non-destructive [40]	Destructive
Key Correlation Metric	Atomic % from peak intensities	Atomic % from peak intensities	Atomic % from ion counts

Standardized Experimental Protocols for Cross-Technique Analysis

The following protocols provide a step-by-step workflow for preparing and analyzing a single sample across XPS, HAXPES, and APT, ensuring data can be meaningfully correlated.

Protocol 1: Unified Sample Preparation and Mounting

Objective: To prepare a single specimen that is compatible with all three techniques, minimizing introduction of contaminants or artifacts.

• Substrate Selection: Use a flat, electrically conductive substrate (e.g., Si wafer, etched metal foil). Clean the substrate sequentially in ultrasonic baths of acetone, isopropanol, and methanol for 10 minutes each, followed by drying under a stream of high-purity nitrogen (≥99.999%).
• Sample Deposition: Deposit the material of interest (e.g., a thin-film coating, nanoparticles) onto the prepared substrate using a controlled method such as physical vapor deposition (PVD) or spin-coating.
• Specimen Sectioning for APT: Using a focused ion beam (FIB) / scanning electron microscope (SEM) system, lift-out and sharpen a microtip specimen (<100 nm diameter at the apex) from a representative region of the coated substrate.
• Reference Marker Creation: Deposit a fiducial marker (e.g., a Pt or W box using electron-beam deposition in the FIB-SEM) near the APT tip location. This allows for re-locating the exact analysis area for the correlative XPS/HAXPES measurements.
• Vacuum Transfer: Mount the sample and the APT tip on a multi-technique holder. Introduce the holder into a vacuum transfer vessel to prevent atmospheric contamination before loading into the respective instruments.

Protocol 2: Data Acquisition with Consistent Parameter Definition

Objective: To acquire data from each technique using parameters that are explicitly defined with ISO 18115-1 terminology to ensure consistency and reproducibility.

• XPS Analysis (Surface Chemistry):

  • Load the sample into the XPS instrument without breaking vacuum from the transfer vessel.
  • Acquire a survey spectrum over a binding energy range of 0-1200 eV to identify all elements present [42] [6].
  • Collect high-energy-resolution spectra for all core levels of interest. Use a monochromatic Al Kα X-ray source (hν = 1.486 keV) and a pass energy of 20 eV.
  • Perform energy calibration by referencing the adventitious C 1s peak to 284.8 eV or a known intrinsic peak [42].
  • Record all acquisition parameters, including X-ray source type, analysis area, and take-off angle, as defined in ISO 18115-1.

• HAXPES Analysis (Bulk & Buried Interface Chemistry):

  • Transfer the sample to the HAXPES instrument without air exposure.
  • Acquire spectra from the same core levels as in XPS using the monochromatic Cr Kα X-ray source (hν = 5.41 keV) [40].
  • Utilize the increased information depth to probe the chemical state of buried interfaces non-destructively [40].
  • Record the photoelectron line and corresponding Auger transitions to calculate the Auger parameter for advanced chemical-state analysis [40].

• APT Analysis (3D Nanoscale Composition):

  • Mount the prepared APT microtip into the instrument.
  • Cool the specimen to a base temperature of 50-60 K.
  • Set the laser pulse energy (for semiconductors/insulators) or voltage pulse fraction (for conductors) to achieve a steady evaporation rate of 5 ions per 1000 pulses.
  • Acquire data until the entire tip specimen has been evaporated, recording the time-of-flight and hit position for every ion.

Protocol 3: Data Analysis and Correlation Using ISO Terminology

Objective: To extract and correlate quantitative information from each dataset using a unified, ISO-compliant vocabulary.

• XPS/HAXPES Quantification:

  • Process spectra using a linear or Shirley background subtraction [42].
  • For quantification, use relative sensitivity factors (RSFs) that are specific to the instrument and X-ray source [42]. Report results as atomic percentages (at%).
  • For peak fitting, constrain model parameters based on physical principles: Full Width at Half Maximum (FWHM) should be consistent for peaks of the same chemical species, and spin-orbit doublet area ratios must adhere to theoretical values (e.g., 2:1 for p orbitals, 3:2 for d orbitals) [42].

• APT Data Reconstruction:

  • Reconstruct the 3D atomic map using software that accounts for the tip's geometry and the experimental conditions.
  • Extract atomic concentration profiles for selected regions of interest (ROIs) to compare with XPS/HAXPES-derived atomic percentages.

• Cross-Technique Data Correlation:

  • Direct Comparison: Create a table comparing the atomic percentages of each element measured by XPS (surface), HAXPES (bulk), and APT (nanoscale volume).
  • Chemical State Correlation: Overlay XPS and HAXPES core-level spectra for the same element to identify binding energy shifts indicative of differential charging or varying chemical environments at the surface versus the bulk.
  • Spatial Correlation: Use the fiducial markers to correlate the APT reconstruction of a specific grain boundary or interface with the HAXPES signature of that same feature, validating the HAXPES interpretation of buried interface chemistry.

Visual Workflow for Cross-Technique Validation

The following diagram illustrates the integrated workflow for correlative analysis, from sample preparation to final data correlation.

The Scientist's Toolkit: Essential Research Reagent Solutions

Successful cross-technique analysis depends on the use of specific, high-purity materials and standardized data processing tools. The following table details these essential items.

Table 2: Essential Research Reagents and Materials for Cross-Technique Analysis

Item Name	Function / Application	Technical Specification / Purpose
High-Purity Silicon Wafer	Standardized substrate for sample deposition	Provides a flat, conductive, and well-characterized surface compatible with all three techniques.
FIB/SEM System	APT tip preparation and site-specific marking	Enables lift-out and sharpening of needle-shaped specimens from specific regions of interest.
Vacuum Transfer Holder	Sample transfer between instruments	Prevents surface contamination and oxidation by avoiding exposure to ambient atmosphere.
ISO 18115-1 Checklist	Data reporting and terminology guide	Ensures consistent use of terms (e.g., "analysis area", "information depth") in metadata and reports.
Standard RSF Library	XPS/HAXPES quantification	Provides instrument-specific relative sensitivity factors for accurate atomic concentration calculation [42].
Adventitious Carbon C 1s	Internal charge reference for XPS/HAXPES	A ubiquitous surface contaminant used to calibrate the binding energy scale to 284.8 eV [42].
Reconstruction Software (IVAS)	APT data analysis	Converts time-of-flight data into a 3D compositional map for direct correlation with HAXPES interfaces.

The integration of XPS, HAXPES, and APT data through the consistent application of ISO 18115-1 terminology provides a powerful, validated approach for understanding complex materials from the surface to the bulk and in three dimensions. The protocols and workflows detailed in this application note offer a concrete path for researchers to overcome the reproducibility challenges in surface science. By standardizing the language and methodology used across these powerful techniques, the scientific community can accelerate discovery, particularly in critical areas like pharmaceutical development where nanoscale surface properties dictate macroscopic performance and efficacy.

The ISO 18115 series serves as the fundamental vocabulary standard for the field of surface chemical analysis, providing critical definitions and terminology that enable clear communication and data interpretation among researchers, scientists, and drug development professionals. This standardized lexicon is particularly vital in spectroscopic analysis where consistent terminology ensures reproducibility across laboratories and instrumentation platforms. Within this framework, ISO 18115-1:2013 specifically establishes the terminological foundation for general concepts and spectroscopic techniques, covering essential terms used in methods such as X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and secondary ion mass spectrometry (SIMS) [3] [43]. The standard comprehensively defines approximately 900 technical terms that describe instrumentation, analytical procedures, data interpretation methods, and measurement phenomena specific to surface analysis techniques [3].

The critical importance of ISO 18115-1 within materials characterization and surface science research cannot be overstated. In pharmaceutical development and research applications, precise surface characterization of materials, implants, or drug delivery systems directly depends on accurate interpretation of spectroscopic data. The standard provides the necessary terminological precision for researchers to effectively communicate findings regarding surface composition, chemical states, contamination levels, and thin film properties. By establishing this unified vocabulary, ISO 18115-1 facilitates collaboration across interdisciplinary teams and ensures that analytical results maintain their validity when shared between research institutions, regulatory bodies, and industrial laboratories. This harmonization is particularly crucial when surface analysis data supports regulatory submissions or quality control processes in drug development pipelines.

Comparative Analysis of Surface Characterization Standards

Tabular Comparison of ISO 18115-1, ISO 18115-2, and ISO 25178

Table 1: Comprehensive comparison of key surface analysis standards

Standard	Scope and Primary Focus	Analytical Techniques Covered	Application Context in Research	Technical Parameters Defined
ISO 18115-1	General terms and terms used in spectroscopy [3] [43]	XPS, AES, SIMS, and related spectroscopic methods [3]	Surface chemical composition analysis, chemical state determination [44]	Binding energy, attenuation length, analysis area, backscattering coefficient [44]
ISO 18115-2	Terms used in scanning-probe microscopy [3]	AFM, STM, SNOM, and related scanned probe methods [3]	Surface topography, nanoscale mechanical properties [3]	Probe-sample interaction, resolution, imaging modes [3]
ISO 25178	Surface texture analysis (not covered in search results)	Optical profilometry, contact profilometry	3D surface topography, roughness quantification	Height parameters, spatial parameters, functional parameters

Interrelationship and Complementary Applications

The relationship between ISO 18115-1, ISO 18115-2, and ISO 25178 represents a comprehensive framework for surface characterization across different dimensional scales and analytical methodologies. While ISO 18115-1 provides the terminological foundation for chemical composition analysis through spectroscopic methods, ISO 18115-2 establishes standardized terminology for structural and topological assessment at nanoscale dimensions through probe microscopy techniques [3]. These complementary standards enable researchers to develop complete surface characterization protocols that integrate both chemical and topological information.

In pharmaceutical research and drug development applications, this integrated approach is particularly valuable for characterizing complex drug delivery systems, implant surfaces, and biomaterial interfaces. For instance, a comprehensive surface analysis of a drug-eluting stent might utilize XPS (terminology defined in ISO 18115-1) to determine surface chemical composition and drug distribution, while applying AFM (terminology defined in ISO 18115-2) to assess surface topography and roughness at the nanoscale. The synergistic application of these standards enables researchers to correlate chemical surface properties with topological features, providing insights into bioavailability, biocompatibility, and functional performance of pharmaceutical products and medical devices.

Experimental Protocols and Methodologies

Protocol 1: Surface Analysis Using X-ray Photoelectron Spectroscopy (XPS)

Principle: XPS analyzes surface chemistry by measuring the kinetic energy of photoelectrons emitted when a material is irradiated with X-rays, providing information about elemental composition, chemical state, and electronic state of elements within the top 1-10 nm of a surface [44].

Sample Preparation:

• For pharmaceutical powders: Prepare a uniform layer on double-sided adhesive tape or press into a indium foil
• For solid formulations: Mount directly on sample holder using conductive tape
• For biological samples: Rapid freezing and transfer under vacuum may be required
• Note: Adventitious carbon referencing may be employed for charge correction of insulating samples [44]

Instrument Calibration and Setup:

• Energy calibration using certified reference materials (e.g., Au 4f7/2 at 84.0 eV)
• Set X-ray source parameters (monochromatic or Al Kα source at 1486.6 eV)
• Configure analyzer settings: constant analyser energy (CAE) mode typically used with pass energy of 20-80 eV for high-resolution scans [44]
• Charge neutralization system activation for insulating samples [44]

Data Acquisition Parameters:

• Survey spectrum: Pass energy 160 eV, energy step 1.0 eV, scan range 0-1400 eV binding energy
• High-resolution regions: Pass energy 20-50 eV, energy step 0.1 eV, appropriate dwell times
• Take-off angle variation for depth profiling (according to definition of analysis volume sample in ISO 18115-1) [44]

Data Interpretation Protocol:

• Identify all elements present from survey spectrum
• Analyze high-resolution regions for chemical state information using chemical shift principles [44]
• Apply appropriate background subtraction (e.g., Shirley background or Tougaard background) [44]
• Calculate atomic concentrations using relative sensitivity factors
• Report results according to ISO 18115-1 terminology for binding energy, peak area, and chemical state [44]

Protocol 2: Compositional Depth Profiling with Sputter Etching

Principle: Sequential surface removal combined with analysis to determine compositional variations as a function of depth, essential for characterizing thin films, coatings, and interfacial regions in drug delivery systems.

Sample Requirements:

• Flat, homogeneous surface area ≥ 2mm × 2mm
• Compatibility with ultra-high vacuum conditions
• Stability under ion beam irradiation

Sputtering Parameters:

• Ion species: Typically Ar+ at 1-5 keV energy
• Ion current density: 0.5-10 μA/cm² calibrated using standard materials
• Raster size: Larger than analysis area to ensure uniform crater base
• Angle of incidence: Typically 45° from surface normal

Analysis Sequence:

• Acquire initial surface spectrum
• Program cyclic sequence: sputter etching for fixed time → analysis of specified regions
• Maintain constant analysis area sample throughout profiling [44]
• Monitor for sputter-induced effects using reference materials

Data Treatment:

• Convert sputter time to depth using crater depth measurements via profilometry [44]
• Apply appropriate corrections for atomic mixing and crater edge effects [44]
• Account for potential preferential sputtering in multi-component systems
• Present results as atomic concentration versus depth according to compositional depth profile terminology [44]

Visualization of Standards Framework and Experimental Workflows

Relationship Diagram of Surface Characterization Standards

Figure 1: Relationship between surface characterization standards

XPS Experimental Workflow According to ISO 18115-1 Terminology

Figure 2: XPS experimental workflow with ISO terminology

Essential Research Reagents and Materials

Table 2: Essential research reagents and materials for surface analysis experiments

Material/Reagent	Function and Application	Technical Specifications	ISO 18115-1 Reference Term
Certified Reference Materials (CRMs)	Energy scale calibration, quantitative accuracy verification	Certified composition and homogeneity	certified reference material [44]
Adventitious Carbon Reference	Charge referencing for insulating samples	Uniform hydrocarbon contamination layer	adventitious carbon referencing [44]
Conductive Mounting Tape	Sample immobilization and electrical contact	Carbon or copper-based adhesives	sample charging [44]
Argon Gas (Research Grade)	Ion source operation for depth profiling	99.999% purity, filtered for hydrocarbons	sputtering parameters [44]
Standard Samples for AES	Auger sensitivity factors determination	Pure elements with certified purity	relative sensitivity factor [44]
Charge Neutralization Flood Gun	Charge compensation for insulating samples	Low-energy electron source	charge neutralization [44]
UHV-Compatible Materials	Sample holders and manipulation components	Low outgassing rates, temperature stability	analysis area sample [44]

Integrated Application in Pharmaceutical Research

The synergistic application of ISO 18115-1 with complementary standards creates a powerful framework for comprehensive surface characterization in pharmaceutical research and drug development. This integrated approach enables researchers to establish robust analytical protocols that address complex challenges in drug formulation, medical device development, and biomaterial engineering. The standardized terminology ensures that analytical data maintains its integrity and interpretability across organizational boundaries and throughout product lifecycle management.

In practice, pharmaceutical researchers apply this integrated standards framework to characterize complex drug delivery systems, optimize manufacturing processes, and troubleshoot product performance issues. For example, the development of controlled-release formulations often requires precise understanding of surface composition and interfacial chemistry between drug particles and polymer matrices. Similarly, the performance of transdermal patches, implantable devices, and inhalation products depends critically on surface properties that can be systematically characterized using techniques standardized through ISO 18115-1 and related documents. This methodological rigor supported by standardized vocabulary is essential for generating reliable data that supports regulatory submissions and quality-by-design initiatives in pharmaceutical development.

In surface spectroscopy research, the reliability of data is paramount. Benchmarking instrument performance through rigorous calibration and verifying resolution is a foundational practice that ensures the accuracy, reproducibility, and comparability of experimental results across different laboratories and studies. This practice is framed within the broader context of ISO 18115-1, which provides the general terms and definitions used in surface chemical analysis. This standard establishes a common language, which is critical for unambiguous communication and quality assurance in scientific research and drug development. Without standardized procedures and definitions, spectral data can be influenced by variations in experimental parameters, making cross-study comparisons difficult and potentially misleading [45]. This application note provides detailed protocols for benchmarking key performance aspects of surface spectroscopy instruments, aligning with standardized terminology to promote data integrity in research and development.

Standard Definitions and Their Importance

Key Terms from ISO 18115-1

Adherence to standardized terminology, as outlined in ISO 18115-1, is the first step in ensuring consistent understanding and implementation of benchmarking protocols. While the specific definitions from ISO 18115-1 are not detailed in the search results, the overarching need for standardization is strongly supported. For instance, a study on Surface Enhanced Raman Spectroscopy (SERS) highlights that variations in experimental parameters such as substrate type, laser wavelength, and sample processing can greatly influence spectral patterns, making results from different research groups difficult to compare [45]. This underscores the critical role of standard definitions in achieving reproducible and comparable results.

The Critical Role of Calibration

Calibration is the process of comparing a measurement device against a reference standard to determine its accuracy and ensure it provides reliable results [46]. In the context of a quality management system, it ensures that all inspection and test equipment used for product, service, and process monitoring is controlled and calibrated against nationally traceable standards at specified intervals [47]. For surface spectroscopy, this is vital because even tiny changes in instrument performance can lead to the misinterpretation of spectral data regarding chemical composition and active sites.

The consequences of poor calibration are significant. Out-of-tolerance (OOT) instruments can lead to unreliable products, customer dissatisfaction, increased warranty costs, and unnecessary rework [46]. Furthermore, in safety-critical fields like medical device development, micro-deviations can result in product failure, injury, or death [48]. Regular calibration is therefore not merely a technical exercise but a strategic practice that impacts product quality, operational efficiency, and regulatory compliance [46] [48].

Quantitative Benchmarks for Instrument Performance

Establishing quantitative benchmarks is essential for objectively assessing instrument status. The following parameters are crucial for benchmarking surface spectroscopy instruments.

Table 1: Key Quantitative Benchmarks for Instrument Performance

Performance Parameter	Definition	Standard/Benchmark	Impact on Data Quality
Calibration Interval	The specified time or usage period between calibrations.	Determined by the instrument owner based on manufacturer recommendations, required accuracy, and OOT history [46].	Prevents data drift, ensures ongoing accuracy and traceability.
Test Uncertainty Ratio (TUR)	The ratio of the accuracy of the instrument under test to the accuracy of the reference standard [46].	A typical commercial calibration uses a reference standard at least four times more accurate than the instrument under test [46].	Defines the confidence level in the calibration process itself.
Spatial Resolution	The ability to distinguish between two adjacent features on a surface.	Advanced surface spectroscopy techniques aim for sub-nanometer resolution to distinguish individual active sites [49].	Determines the level of detail and specificity in surface mapping.
Temporal Resolution	The speed at which measurements can be taken.	Critical for capturing dynamic processes; many catalytic events occur on femtosecond to picosecond timescales [49].	Enables the study of dynamic surface reactions and active site behavior.

Experimental Protocols for Calibration and Benchmarking

General Calibration Workflow for Quality Management

A robust calibration process is a multi-step procedure that integrates into an organization's Quality Management System (QMS). The following workflow outlines the key stages, which are applicable to a wide range of measurement equipment, including surface spectroscopy instruments.

Title: General Calibration Workflow

Protocol Steps:

• Identify Equipment and Determine Requirements: Create and maintain a controlled equipment log of all instruments requiring calibration. For each instrument, define the required measurements, tolerances, and calibration interval based on manufacturer guidelines, usage, and required accuracy [47] [46] [48].
• Control the Operational Environment: The environment where calibration is performed must be controlled. Factors like temperature, humidity, and cleanliness can significantly impact calibration results and must be monitored regularly to prevent discrepancies [50] [46].
• Execute Calibration: Calibration must be performed by competent personnel using reference standards traceable to national or international standards (e.g., NIST). The process involves comparing the instrument's reading to the standard and documenting the "as found" data [50] [46] [48].
• Record Results and Analyze Conformance: Maintain full calibration records, including calibration certificates. Compare the results against the defined tolerances. If the instrument is out-of-tolerance (OOT), initiate a non-conformance report and investigate the potential consequences on recent measurements [46] [48].
• Take Corrective Actions and Release: For OOT instruments, take corrective actions which may include adjustment ("optimization"), repair, re-testing of affected products, or even product recall. After adjustment, "as left" data is recorded. The instrument is then labeled with its calibration status and next due date before being returned to service [46] [48].

Protocol for Benchmarking Spectral Reproducibility in SERS

The following protocol is adapted from a direct comparison study of SERS protocols for human serum analysis, illustrating a specific application of benchmarking in surface spectroscopy [45].

Aim: To evaluate and benchmark the performance of a Surface Enhanced Raman Spectroscopy (SERS) instrument and methodology by assessing the repeatability of spectral outputs using different preparation protocols.

Principle: Different sample preparation protocols can significantly influence spectral intensity and repeatability. Benchmarking involves running the same sample through different validated protocols to quantify variability and identify the most robust method [45].

Table 2: Research Reagent Solutions for SERS Benchmarking

Reagent/Material	Function in the Experiment
Human Serum Sample	The complex biological matrix under investigation.
Silver Nanoparticles (Ag NPs)	The SERS-active substrate that enhances the Raman signal.
Deproteinization Agents	Chemicals used to remove proteins, reducing sample complexity and matrix effects.
Reference Standard	A standard solution for verifying the instrument's spectral wavelength and intensity accuracy.

Methodology:

• Sample Preparation: Prepare aliquots of the same human serum sample according to five different SERS protocols. This includes two commonly used literature protocols and three "in-house" protocols. Key variables to test include:
  • Substrate Type: Use the same batch of Ag nanoparticles for all tests to control for this variable.
  • Nanoparticle Concentration: Vary the ratio of serum to nanoparticle suspension.
  • Incubation/Deproteinization: Include protocols with and without deproteinization steps.
  • Laser Power: Use consistent laser power across measurements for comparability [45].
• Data Acquisition: Acquire SERS spectra for each sample preparation protocol. Ensure all instrumental parameters (laser wavelength, acquisition time, etc.) are identical for all runs, except for the variable being tested.
• Data Analysis:
  • Spectral Intensity Comparison: Compare the overall spectral intensity obtained from each protocol.
  • Repeatability Assessment: Calculate the standard deviation or coefficient of variation for multiple replicates (n≥5) for each protocol. Protocols with lower variability are more repeatable.
  • Pattern Recognition: Perform a Principal Component Analysis (PCA) on the spectral dataset. Protocols that show tight clustering in the PCA scores plot (e.g., Protocol 1 and 3 from the cited study) are considered to have the least variability and highest repeatability [45].

The Scientist's Toolkit: Essential Materials for Surface Analysis

The following table details key reagents and materials essential for conducting rigorous surface analysis and calibration, as derived from the cited protocols.

Table 3: Essential Reagents and Materials for Surface Spectroscopy

Item	Function	Example Use Case
Traceable Reference Standards	Calibrate instruments against national/international standards to ensure measurement traceability [50] [46].	Verifying the accuracy of wavelength and intensity readings in Raman or XPS spectrometers.
SERS-Active Substrates	Enhance the Raman signal by several orders of magnitude for sensitive detection [45] [49].	Enabling the detection of trace amounts of active species in biofluids or on catalyst surfaces.
Calibration Management Software	Streamline the calibration process via automated scheduling, real-time tracking, and record-keeping [46].	Managing a database of equipment, calibration due dates, and certificates for audit compliance.
Multimodal Spectroscopy Setups	Combine complementary methods (XPS, FTIR, Raman) to overcome the limitations of individual techniques [49].	Providing a comprehensive understanding of surface composition, structure, and active sites.

Benchmarking instrument performance through standardized calibration and resolution checks is a non-negotiable practice in high-quality surface spectroscopy research. By adhering to standard definitions like those in ISO 18115-1 and implementing the detailed protocols outlined in this application note, researchers and drug development professionals can ensure their data is accurate, reproducible, and comparable. This rigorous approach not only fulfills quality standards like ISO 9001 and ISO 13485 but also builds a foundation of trust in scientific findings, ultimately accelerating innovation and ensuring safety in critical applications.

Conclusion

The adoption of ISO 18115-1:2023 is not merely an academic exercise but a fundamental requirement for robust and reproducible science in surface chemical analysis. By providing a common language, this standard bridges communication gaps between researchers, enables valid comparison of data across different laboratories and instruments, and directly supports quality assurance in biomedical research and drug development. The recent updates, which include terms for emerging techniques like atom probe tomography and near-ambient pressure XPS, ensure the standard remains relevant. As surface analysis continues to evolve, particularly in complex biological interfaces, the consistent application of this vocabulary will be crucial for accelerating innovation, ensuring regulatory compliance, and building a reliable knowledge base for future clinical applications.

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