USE OF GAS-LIQUID-CHROMATOGRAPHY WITH ELECTRON-CAPTURE AND THERMIONIC-SENSITIVE DETECTION FOR THE QUANTITATION AND IDENTIFICATION OF PESTICIDE-RESIDUES

A gas chromatographic methodology that exploits combination of differe nt columns and different detectors for testing residues of over 150 pe sticides is proposed. Two gas-liquid chromatographs were set up each w ith two capillary columns of different polarities, DB-5 and DB-1701. E ach column was connected to a precolumn with deactivated silica which was in turn connected to the injector, Each column was coupled to an e lectron-capture detector in one instrument and a thermionic-sensitive detector in the other. Standard solutions containing each pesticide, w ith ethion used as a reference peak to calculate the relative retentio n time (RRT), were injected into each gas chromatograph. RRT values fo r each column-detector combination are reported, Two columns of differ ent polarities allowed identification and separation of most of the pe sticides studied. Qualitative confirmations achieved by comparing the RRT values obtained by columns of different polarities on the same det ectors as well as on different detectors are discussed. The instrument al configuration and the analytical conditions used may be a useful to ol for the determination and confirmation of the great number of pesti cides residues that may be extracted by multiresidue methods.