Dynamic Polluted Atmosphere Generator at Low ppbv Levels for Validating VOC Sampling Methods
Résumé
A reconstituted VOC atmosphere generator in the ppbv-pptv range is presented. Designed for dynamic mode operation, this generator continuously monitors the generated atmospheric concentration by UV spectrophotometry using an optical tracer, styrene, which is a strong UV absorber. In the ppbv range, the tracer is detected using a multipath White cell with signal recovery by a lock-in amplifier. The VOCs are injected in the liquid phase. By diluting these compounds in the liquid phase, it is also possible to generate atmospheres in the pptv range. The behavior of the tracer reflects the behavior of all the other compounds injected simultaneously. Generator operation and characteristics of the dynamic atmosphere were checked by chromatography. Among other applications, this apparatus can be used to investigate various sampling techniques using known atmospheres. As an example of an application, percentage recovery of compounds in a complex atmosphere was studied on Tenax GC and Carbotrap B.