Standard Operating Procedures (SOPs) for Air Sampling in Stainless Steel Canisters for Non-Methane Hydrocarbons Analysis
This document gives guidance for sampling of atmospheric volatile non-methane hydrocarbons (NMHCs) in whole air using electro-polished stainless steel canisters in the WMO GAW network. The described procedures are appropriate for alkanes, alkenes, alkynes, and aromatic compounds with two to six carbon atoms (C2 to C6). NMHCs with more than six carbon atoms tend to be adsorbed on the canister surfaces and may only be partially recovered. The procedures are valid for analyzing volatile alkane, alkyl and isoprene mole fractions in continental background air with mole fractions at pmol/mol levels as well as for ambient air in and around urban areas in the range of µmol/mol. With caution, also mole fractions of alkenes and aromatics may be reported but at µmol/mol level only. These compounds tend to form artefacts in stainless steel canisters. Thus air sample storage time is recommended to be as short as possible before analysis. Hence, under conditions of normal usage for sampling ambient air, most NMHCs can be recovered from canisters near their original concentrations after storage times of up to thirty days (US-EPA, 1999). According to monitoring requirements, the sampling time may vary from seconds to several hours. From the canister samples the target compounds are then typically analysed by gas chromatography using flame ionisation detection and/or mass spectroscopy.
Collection(s) and Series: GAW Report- No. 204
Format: Digital (Free)