Evaluation of the reliability of diffusive sampling in environmental monitoring

Diffusive sampling has long been available as an alternative to active samp ling in occupational hygiene to determine the concentrations of toxic volat ile organic compounds in workplace air. Diffusive sampling has many advanta ges including increased sampling time, simplicity and lower unit sample cos t. On the other hand, its application in environmental monitoring is ambigu ous, because the reliability of this technique under environmental conditio ns is subject to much controversy. The main question is whether the simple uptake model of diffusive sampling can be applied under environmental condi tions. In this paper, the applicability of the simplified uptake model of diffusiv e sampling for benzene, toluene, ethylbenzene and m,p-xylene (BTEX compound s) was studied in the environment. It was found that a critical exposure do se should be exceeded to obtain consistent and reliable analytical data and to ensure that the simplified uptake theory is useful. It was concluded th at the main source of uncertainty in environmental applications of diffusiv e sampling was the use of uptake rates determined in the laboratory. Althou gh the uptake rates seem to be stabilised when the critical exposure limit is exceeded, their determination requires field comparison with a standard reference method. (C) 2000 Elsevier Science B.V. All rights reserved.