DETERMINATION OF VOLATILE ORGANIC-COMPOUNDS IN AIR USING A DEHUMIDIFIED AND VENTILATED DIFFUSIVE SAMPLER, THERMAL-DESORPTION AND GAS-CHROMATOGRAPHY WITH FLAME IONIZATION DETECTION

A portable dehumidified and ventilated diffusive sampler (DVDS) incorp orating three diffusive tubes and a domestic battery-driven fan dryer was developed to solve the problems of high humidity and stagnant air for environmental monitoring of volatile organic compounds (VOCs), Usi ng Tenax GR as adsorbent, thermal desorption and cryogenic on-column f ocusing prior to capillary GC analysis with flame ionization detection , the 10 most common aromatic and halogenated VOCs were determined wit h the DVDS, giving linear working ranges 3.2 mu g m(-3)-770 mg m(-3) f or 1 h sampling, sampling rates of 0.64-0.98 ml h(-1) and RSD of 4-6%. The good repeatability is due to the use of a small-diameter diffusiv e tube (0.32 mm id) and reproducible ventilation in the DVDS. The opti mized analytical parameters are temperature 10-40 degrees C, relative humidity 0-100%, sampling time 15-480 min and storage for up to 21 day s. Quality assurance procedures were developed for the calibration and preparation of the DVDS. The reliability of the method was establishe d by parallel determinations at a given field station using both the D VDS and the active sampling method.