AUTOMATED GAS-CHROMATOGRAPH MASS-SPECTROMETER FOR ROUTINE ATMOSPHERIC FIELD-MEASUREMENTS OF THE CFC REPLACEMENT COMPOUNDS, THE HYDROFLUOROCARBONS AND HYDROCHLOROFLUOROCARBONS

An automated gas chromatograph/mass spectrometer is described for the routine field monitoring of the CFC replacement compounds, the hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs). Detection limits of 0.5 pptv are achieved by concentration of a 2-L air sample onto a three-stage adsorbent-filled microtrap. The microtrap is cooled to subambient temperatures (-50 degrees C) using Peltier thermoelectric devices, without a post-desorption cryofocussing step, thereby eliminating the need for liquid cryogens. The enriched air sample is thermally desorbed by direct ohmic heating of the microtrap, and compounds are separated on a 100-m, 5-mu m-thick film high-resolution capillary column. Individual hydrohalocarbons are determined by selected ion masses for quantitation. The instrument is designed to operate automatically at a remote atmospheric research station providing similar to 2-h replicate air and calibration analyses.