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 different columns and different detectors for testing residues of over 150 pesticides is proposed. Two gas-liquid chromatographs were set up each with two capillary columns of different polarities, DB-5 and DB-1701. Each column was connected to a precolumn with deactivated silica which was in turn connected to the injector, Each column was coupled to an electron-capture detector in one instrument and a thermionic-sensitive detector in the other. Standard solutions containing each pesticide, with ethion used as a reference peak to calculate the relative retention time (RRT), were injected into each gas chromatograph. RRT values for each column-detector combination are reported, Two columns of different polarities allowed identification and separation of most of the pesticides studied. Qualitative confirmations achieved by comparing the RRT values obtained by columns of different polarities on the same detectors as well as on different detectors are discussed. The instrumental configuration and the analytical conditions used may be a useful tool for the determination and confirmation of the great number of pesticides residues that may be extracted by multiresidue methods.