Ambient air - Method for the determination of the concentration of nitrogen dioxide by diffusive sampling
This European Standard specifies a method for the sampling and analysis of NO2 in ambient air using diffusive sampling followed by extraction and analysis by colorimetry or ion chromatography (IC). It can be used for the NO2 measurement in a concentration range of approximately 3 µg/m³ to 130 µg/m3. A sample is typically collected for a period of 1 to 4 weeks , with exposure periods depending on the design of the samplers and the concentration levels of NO2.
Several sorbents can be used for trapping NO2 in ambient air using a diffusive sampler. This standard specifies the application of triethanolamine as the reagent.
Nitrous acid and peroxyacetyl nitrate are the major chemical interferences of sorption by triethanolamine. However, in ambient air monitoring over long sampling times, both contaminants are generally present at low concentrations relative to NO2. Moreover, these species can also interfere with the measurement of NO2 when applying the EU reference method for NO2 monitoring based on chemiluminescence (see ).
This standard describes the application of a tube-type sampler with either a cylindrical or a slightly conical tube. Its typical uptake rate is about 1 cm3/min. Only for this sampler type sufficient evidence of validation has been found in a literature survey .
The relative expanded uncertainty of NO2 measurements performed using these tube-type diffusive samplers can potentially be lower than 25 % for individual measurements. When aggregating results to form annual average values, the relative expanded uncertainty can be further reduced to levels below 15 % due to the reduction of random effects on uncertainty .