Overview - ISO 13084:2018 (ToF‑SIMS mass calibration)
ISO 13084:2018 specifies a practical, instrument‑agnostic method to optimize and calibrate the mass scale of time‑of‑flight (ToF) secondary ion mass spectrometers (SIMS) for general analytical use. The standard targets improved mass accuracy for molecular and surface chemical analysis by specifying sample preparation, spectral acquisition, peak measurement and iterative optimization steps that together yield reproducible, high‑accuracy mass calibration.
Key topics and technical requirements
- Scope: Applicable only to ToF‑SIMS instruments; not restricted to specific instrument designs.
- Reference sample: Use a thin (≈10–100 nm) polycarbonate (PC) film on a conducting substrate (e.g., silicon) prepared from PC in THF (spin casting recommended).
- Optimization set: The method uses a defined set of 19 CxHy (hydrocarbon) peaks from PC spectra to optimize instrument parameters before final calibration.
- Acquisition guidance: Select acquisition conditions giving a maximum mass ≥ 800 u and ensure sufficient counts (recommend >10 000 counts in a representative CxHyO peak) without detector saturation or exceeding recommended ion fluence.
- Peak measurement: Fit peaks using an asymmetric Gaussian model and use intensities above 50% of peak maximum to determine peak centres for accurate mass measurement.
- Performance targets: The introduction notes that modern analysis often requires relative mass accuracy far better than typical interlaboratory results; the procedure reduces mass calibration errors and limits extrapolation errors for large molecules.
- Documentation and uncertainty: Includes calibration procedures, iterative optimization of instrumental parameters, and informative annexes on calibration uncertainty and an internal addition method.
Applications and who uses this standard
ISO 13084:2018 is intended for:
- SIMS instrument operators and laboratory analysts performing surface chemical analysis of organics and inorganics.
- Analytical and surface chemistry laboratories seeking reproducible, traceable ToF‑SIMS mass calibration.
- Quality assurance teams and accreditation bodies that require documented calibration procedures and uncertainty assessment.
- Instrument manufacturers and service engineers who provide recommended operating/maintenance procedures and software for peak fitting and calibration.
Practical benefits include improved mass accuracy for molecular identification, reduced interlaboratory variability, and better confidence when distinguishing ions with near‑isobaric masses.
Related standards and references
- ISO 23830 (acquisition best practices for high‑quality SIMS spectra) is referenced for spectral repeatability and constancy.
- Prepared by ISO/TC 201 (Surface chemical analysis) - consult national bodies or ISO for implementation details.
Keywords: ISO 13084:2018, ToF‑SIMS, mass calibration, mass accuracy, polycarbonate reference, asymmetric Gaussian peak fitting, calibration uncertainty.