Overview
ISO 8186:1989 specifies a gas chromatographic method for determining the mass concentration of carbon monoxide (CO) in ambient air. The procedure is designed for low-level measurements (two principal ranges: 0–1 mg/m3 and 0–25 mg/m3), but can be applied to concentrations up to 1 000 mg/m3 at 25 °C and 101.3 kPa. With careful operation, concentrations below 1 mg/m3 are attainable. The method uses gas chromatography (GC) with a flame ionization detector (FID) after catalytic conversion of CO to methane.
Key topics and technical requirements
- Principle: Separation of CO from other air constituents on a chromatographic column, catalytic reduction of CO to methane, detection by FID.
- Converter: Nickel-based catalyst (prepared from nickel nitrate on diatomaceous earth). Typical conversion temperature ~260 °C; initial conditioning/activation steps may use higher temperatures. Converter efficiency must be verified.
- Detector and carrier: FID with hydrogen as carrier and reducing gas; air, nitrogen or helium may be used for burner optimization. Gases used must meet purity limits to avoid false signals.
- Sampling system: Discrete-sample automatic switching using a sampling loop (approx. 4 cm3) and pump (~100 cm3/min). Column back-flushing is required between injections to avoid retention of water or slow-eluting components. Up to ~10 discrete samples per hour are possible depending on timing.
- Calibration and quality control: Use certified calibration gas mixtures (CO in air or nitrogen; methane in air for converter efficiency). At least four calibration points (including zero) are required across the selected measurement range. Converter efficiency is confirmed by comparing peak areas from methane and CO standards.
- Operational cautions: Maintain heated transfer lines (above ~100 °C) to prevent water condensation; control moisture and hydrocarbon contents in gases; follow safety precautions handling flammable gases (H2, CH4).
Applications and users
ISO 8186:1989 is intended for:
- Ambient air quality monitoring where accurate low-level CO measurement is required
- Research and air pollution studies assessing CO concentrations from various sources
- Environmental laboratories, regulatory agencies, and monitoring networks requiring traceable GC/FID CO analysis
- Instrument manufacturers and calibration gas suppliers implementing or supporting GC-based CO measurement systems
Related standards
- ISO 6143 - Gas analysis: determination of composition of calibration gas mixtures (comparison methods)
- ISO 6144 - Gas analysis: preparation of calibration gas mixtures (static volumetric methods)
- Prepared by ISO/TC 146 (Air quality)
Keywords: ISO 8186:1989, ambient air, carbon monoxide measurement, gas chromatographic method, GC-FID, converter, calibration, air quality monitoring.
