COMPARISON OF A PULSED ELECTRON-CAPTURE DETECTOR AND A FOURIER-TRANSFORM ION MOBILITY DETECTOR AFTER CAPILLARY SUPERCRITICAL FLUID CHROMATOGRAPHY

A commercial electron capture detector and an ion mobility detector were interfaced to a supercritical fluid chromatograph (SFC). The ion mobility detector (IMD) was operated in the negative ion collection mode wherein analyte molecules of high electron affinity form negatively charged ions in the detector, producing an ECD-like response. Responses of the two detectors were compared using pressure programmed SFC with carbon dioxide as the mobile phase. A mixture of nine chlorinated pesticides (Lindane, DDT, DDE, BHC, Endrin, Heptachlor, Endosulfan, Dieldrin and Chloropicrin); a mixture of six polycyclic aromatic hydrocarbons (naphthalene, acenaphthalene, dimethylnaphthalene, pyrene, phenanthrene, and fluoranthene); two polychlorinated biphenyls (Aroclor 1248 and Aroclor 1260), and a bean extract containing the chlorinated fungicide Captan were chromatographed as test compounds. In all cases pressure programming of the carbon dioxide mobile phase resulted in an increasing baseline signal as pressure increased with the ECD while a stable baseline was observed with the IMD. These investigations demonstrated the potential of negative mode IMD as a useful alternative for the sensitive and selective SFC detection of compounds amenable to electron capture detection.