Use of capillary gas chromatography with negative ion-chemical ionization mass spectrometry for the determination of perfluorocarbon tracers in the atmosphere

A sensitive and selective technique for the quantitative measurement of atm ospheric perfluorocarbon trace species at the sub part per quadrillion (10( -15)) levels is presented. The method utilizes advances in adsorbent enrich ment techniques coupled with benchtop capillary gas chromatography and nega tive ion-chemical ionization mass spectrometry. The development and enhance ment of sampling technology for tracer experiments is described, and the re sults from background measurements and a preliminary field experiment are p resented. The overall precision of the analytical method with respect to th e preferred tracer for these atmospheric transport studies, perfluoromethyl cyclohexane, was +/-1.7%. The background concentrations of perfluorodimethy lcyclobutane, perfluoromethyleyclopentane, and perfluoromethylcyclohexane a t a remote coastal location (Mace Head, Ireland, 53 degreesN, 10 degreesW) were found to be 2.5 (+/-0.4), 6.8 (+/-1.0), and 5.2fL.L-1 (+/-1.3), respec tively. Background concentrations within an urban conurbation (Bristol, U.K .) were slightly greater at 3.0 (+/-1.5), 8.1 (+/-1.8), and 6.3 fL L-1 (+/- 1.1), respectively.