Peculiarities in the gas-liquid chromatographic analysis of fenamiphos sulphone

Abstract

Toxic residues of fenamiphos (ethyl 4-methyl-m-tolyl isopropylphosphoramidate) are present in plants as two metabolites, fenamiphos sulphoxide and fenamiphos sulphone, which are determined together as the sulphone after oxidation of the sulphoxide. Different gas-liquid chromatographic columns however, produced different chromatograms. From chromatograms produced by samples fortified with fenamiphos sulphoxide and fenamiphos sulphone that were injected on to Carbowax 20M and Reoplex 400 columns, it seemed as if the oxidation step was unsuccessful because two peaks appeared on the chromatogram corresponding to the retention times of the sulphoxide and the sulphone. When the same samples were injected on to a DC 200 column, only sulphone peaks appeared on the chromatogram.