ISO 19229:2019

Overview - ISO 19229:2019 (Gas analysis - Purity analysis and the treatment of purity data)

ISO 19229:2019 defines requirements for the purity analysis of materials (gases and liquids) used to prepare calibration gas mixtures and for the use of purity data when calculating the final composition of those mixtures. The standard focuses on consistent treatment of impurity data to support metrological traceability, reliable uncertainty budgets and accurate certification of calibration gases.

Key topics and technical requirements

• Identification of potential impurities: guidance on compiling impurities from literature, material information, production process and past experience.
• Classification of impurities: criteria for critical impurities (those that affect analytical verification or react with components) and significant impurities (those contributing >10% of the target uncertainty).
• Purity analysis approaches:
  • Traceable purity analysis - calibration of analysers with defined calibration gas mixtures; methods referenced include ISO 6143 and ISO 12963.
  • Indicative purity analysis - reduced rigor when full traceability is not needed; still documents limitations and uncertainties.
  • No purity analysis - procedures for estimating unmeasured but expected impurities when analysis is impractical.
• Analytical techniques and considerations: examples include GC-FID, GC-TCD, GC-DID, and laser spectroscopy; use of relative response factors (RRF), standard addition methods, purifier efficiency and limits of detection (typically analyzer LOD ≈ 1/10 of target impurity).
• Use of purity data in calculations: procedures to calculate amount-of-substance, mass and volume fractions of the most abundant component and how to propagate uncertainties.
• Coverage intervals and certificates: methods for setting coverage intervals and preparing certificates for calibration gas mixtures.
• Worked examples: practical examples provided in Annex A to illustrate calculations and uncertainty treatment.
• Referenced metrology guidance: ISO/IEC Guide 98-3 (GUM) for uncertainty evaluation.

Applications - who should use ISO 19229:2019

• Laboratories preparing or certifying calibration gas mixtures (gravimetric, volumetric, static or dynamic methods).
• National metrology institutes and calibration providers ensuring traceability of gas standards.
• Industrial gas suppliers, environmental and emissions testing labs, and instrument manufacturers that require robust purity data and uncertainty statements.
• Quality managers and metrologists responsible for analytical verification and certification of gas composition.

Related standards

• ISO 6141 - Contents of certificates for calibration gas mixtures
• ISO 6143 - Comparison methods for determining composition of calibration gas mixtures
• ISO 7504 - Gas analysis vocabulary
• ISO 12963 - Comparison methods for calibration of gas mixtures
• ISO 14912 - Conversion of gas mixture composition data
• ISO/IEC Guide 98-3 (GUM) - Uncertainty of measurement

Keywords: ISO 19229:2019, gas analysis, purity analysis, calibration gas mixtures, purity data, metrological traceability, impurities, gas chromatography, laser spectroscopy, uncertainty.