DYNAMIC POLLUTED ATMOSPHERE GENERATOR AT LOW PPBV LEVELS FOR VALIDATING VOC SAMPLING METHODS

A reconstituted VOC atmosphere generator in the ppbv-pptv range is pre sented. Designed for dynamic mode operation, this generator continuous ly monitors the generated atmospheric concentration by UV spectrophoto metry using an optical tracer, styrene, which is a strong UV absorber. In the ppbv range, the tracer is detected using a multipath White cel l with signal recovery by a lock-in amplifier. The VOCs are injected i n the liquid phase. By diluting these compounds in the liquid phase, i t is also possible to generate atmospheres in the pptv range. The beha vior of the tracer reflects the behavior of all the other compounds in jected simultaneously. Generator operation and characteristics of the dynamic atmosphere were checked by chromatography. Among other applica tions, this apparatus can be used to investigate various sampling tech niques using known atmospheres. As an example of an application, perce ntage recovery of compounds in a complex atmosphere was studied on Ten ax GC and Carbotrap B.