cen:proj:78115

Ambient air — Standard method for the measurement of organic ozone precursor concentrations — Part 2: Pumped sampling followed by thermal desorption and gas chromatography cen:proj:78115

Scope

This document gives general guidance for the time-weighted average monitoring of organic ozone precursor vapours (VOCs) in air by pumped sampling onto sorbent tubes followed by off-line analysis using thermal desorption and capillary gas chromatography. This document is valid for the measurement of organic ozone precursor vapours ranging in volatility from C3 to C14 hydrocarbons in a concentration range of approximately 0,5 μg/m3 to 50 μg/m3. Air samples are typically collected over periods ranging from a few hours to 7 days. Airborne concentrations of less volatile compounds can also be measured using this document provided appropriate sorbents are used in the samplers. The upper limit of the useful range is set by the sorptive capacity (the safe sampling volume) of the sorbent and by the linear dynamic range of the gas chromatograph column and detector or by the sample splitting capacity of the analytical instrumentation used. The lower limit of the useful range depends on the noise level of the detector and on blank levels of interfering artefacts on the sorbent and in the analytical system. Artefacts are typically low ng or sub ng for sample tubes packed with graphitised carbon sorbents or carbonised molecular sieves, but higher levels of organic compounds have been noted in tubes packed with other sorbents, e. g. porous polymers. The detection limit will be approximately 1/10 of the lower concentration range. This document provides general guidance for the sampling of organic ozone precursor vapours using either a single sampler, which is changed manually after every exposure period, or a multi-tube sampler capable of storing and exposing multiple samples sequentially without user intervention.

Related legislation

Legislation related to this standard