SIMULTANEOUS DUAL-COLUMN, DUAL-DETECTOR GAS-CHROMATOGRAPHIC DETERMINATION OF CHLORINATED PESTICIDES AND POLYCHLORINATED-BIPHENYLS IN ENVIRONMENTAL-SAMPLES

The lack of confirmation of Identified analytes In environmental gas chromatography (GC) that uses the traditional one-column, one-detector systems (e.g., GC-electron capture detection with a nonpolar column) often raises questions as to the validity of the data. To avoid misidentification of chlorinated pesticides and polychlorinated biphenyls (PCB), we conducted simultaneous dual-column, dual-detector GC analysis. Within one GC instrument, injected sample extracts were spilt In two and each portion passed through a capillary column of different polarity. A traditional nonpolar column, DB-5, was connected to an electron capture detector for initial identification of analytes; a more polar column, DB-17, was used with the halogen-specific electrolytic conductivity detector for confirmation analysis. GC column retention characteristics were determined for a large set of environmentally important pesticides and PCB congeners for the DB-5 and DB-17 analytical columns. The dual-column, dual-detector system was then evaluated on a large number of environmental samples of different matrix types. Results indicated that a substantial number of analytes, especially pesticides, may be incorrectly identified In environmental samples with one-column, one-detector systems. Use of a simultaneous dual-column, dual-detector system, substantially decreases the risk of false-positive Identifications without significantly Increasing the cost or time of analysis. © 1990, American Chemical Society. All rights reserved.