Overview
EN ISO 6145-11:2008 - Gas analysis: Preparation of calibration gas mixtures using dynamic volumetric methods - Part 11: Electrochemical generation specifies a method to prepare calibration gas mixtures by electrochemically generating a calibration component and introducing it into a complementary carrier (complementary gas) flow. The method is applicable to very low-volume-fraction ranges ((0.1 to 250) × 10^-6) and requires the relative expanded uncertainty of the calibration gas content, U (k = 2), to be ≤ 5%. This part of ISO 6145 is intended for calibration gas preparation where stability in cylinders is problematic (corrosive or very low concentration components).
Key Topics
- Principle of generation: Quantity of gas generated is proportional to electrical charge passed; linked to the Faraday constant (F = 96 485.3415 C·mol^-1 as given).
- Complementary gas flow: Preparation requires accurate volumetric control of the carrier gas flow; flow determination methods reference ISO 6145-1.
- Electrolytic cell and apparatus: Cell construction, current supply, flow control and design requirements to ensure efficient transfer of generated component to the gas stream. Clause 5 lists operational conditions and cell efficiency considerations.
- Uncertainty evaluation: Identification and treatment of uncertainty sources (complementary gas flow, generation current/charge, absorption in electrolyte, moisture, temperature, chemical purity, impurities).
- Applicable gases: Examples include O2, H2, HCN, H2S, Cl2, Br2, ClO2, NH3, NO, N2, CO2, PH3, AsH3 and O3 (as noted in the standard).
- Practical components: Examples and schematics provided in annexes (cell designs, electrical supply, decomposition voltages) and a commercial system example (Annex A).
Applications
- Who uses it: calibration gas producers, analytical laboratories, environmental and emissions monitoring labs, instrument manufacturers, process control engineers, and calibration service providers.
- When to use: preparing stable, low-concentration or corrosive calibration mixtures that are unsuitable for high-pressure cylinders; rapid on-demand generation of calibration standards.
- Integration: commonly combined with thermal mass-flow controllers and automated control/computerization for precise, reproducible electrochemical gas blending.
Related Standards
- ISO 6145-1 - Methods of calibration (dynamic volumetric methods)
- ISO 6143 - Comparison methods for checking composition of calibration gas mixtures
- ISO 6145-7 - Thermal mass-flow controllers
Keywords: EN ISO 6145-11:2008, electrochemical generation, calibration gas mixtures, gas analysis, dynamic volumetric methods, electrolytic cell, complementary gas flow, uncertainty.