ISO 6142-1:2015

Overview

ISO 6142-1:2015 - Gas analysis: Preparation of calibration gas mixtures - Part 1: Gravimetric method for Class I mixtures specifies a gravimetric (weighing) method for preparing high-accuracy calibration gas mixtures in cylinders. The standard establishes procedures to produce mixtures with traceable amount-of-substance fractions (amount fractions) and describes how to calculate and document the uncertainty of each component. It applies only to gaseous or fully vaporized components (introduced as gas or liquid) and covers both binary and multi-component mixtures, including natural-gas type mixtures. It is intended for Class I (individually verified) mixtures and excludes batch production of multiple mixtures in a single process and mixtures with unintended reactive components.

Key topics and requirements

• Gravimetric preparation: Determining masses added by weighing supply or receiving cylinders before and after addition.
• Traceability to SI: Conversion of masses to amounts of substance using chemical purity and atomic/molar masses.
• Uncertainty evaluation: Systematic calculation of uncertainty contributions from:
  • weighing process and balance performance
  • purity and quantified impurities of parent gases/liquids
  • mixture homogeneity and stability over intended shelf life
  • verification against independent reference mixtures
• Purity analysis: Requirement to assess and quantify impurities in each parent gas or liquid.
• Homogeneity and stability testing: Guidance on assessing within-cylinder homogeneity and time-dependent stability (decay rates) and including these in uncertainty budgets.
• Verification: Individual analytical verification of the final mixture composition for Class I mixtures.
• Practical precautions: Handling, weighing, filling guidance and rules to avoid condensation or reactions; Annexes cover liquid introduction, molar masses, examples and calculation derivations.

Applications and users

ISO 6142-1 is essential for organizations that require high-accuracy calibration gases and documented measurement uncertainty:

• Calibration gas manufacturers preparing Class I mixtures
• Accredited analytical/metrology laboratories issuing traceable reference gases
• Environmental monitoring and air quality labs (emissions, ambient monitoring)
• Petrochemical and natural gas instrumentation calibration
• Instrument manufacturers and QA/QC teams needing verified reference standards
• Accreditation bodies and quality managers implementing traceability and uncertainty procedures

Related standards

Relevant ISO documents referenced or complementary to ISO 6142-1:

• ISO 6141 (certificates for calibration gas mixtures)
• ISO 6143 (comparison methods for checking composition)
• ISO 7504, ISO 14912, ISO 16664, ISO 19229, ISO/TS 29041
• ISO/IEC Guide 98-3 (GUM: uncertainty of measurement)

Keywords: ISO 6142-1, gravimetric method, calibration gas mixtures, uncertainty, traceability, purity analysis, gas analysis, cylinder filling, amount-of-substance fraction.