An integrated gas chromatographic method towards the simultaneous determination of phosphoric and amino acid group containing pesticides

Ampropylfos, glyphosate, glufosinate and bialaphos are water soluble pestic ides that contain phosphoric and amino acid groups in their molecules. Thei r polar nature and high water solubility make extraction difficult and limi t the options for using the various derivatization techniques often employe d for gas chromatographic analysis. A multiresidue method is proposed that allows the simultaneous determination of six analytes (pesticides and some of their metabolites) in environmental waters down to sub-mu g L-1 levels. A mixture of trifluoroacetic anhydride and trifluoroethanol converts them i n a single-step reaction to derivatives that are sufficiently volatile for gas chromatographic analysis. Electron capture and mass-selective detection are used for quantitation purposes, and their analytical characteristics a re presented. Under the chromatographic conditions employed, acceptable sep aration is attained for the derivatized analytes, with both glufosinate and bialaphos emerging as double peaks. Recoveries of spiked environmental wat er samples range from 88 to 106%. The mean relative standard deviation of t he method does not exceed 3.0%, whereas, depending on the detection system, the limits of detection for the analytes are in the range of 0.09-65 mu g L-1, the upper value being the bialaphos detection limit.