DETERMINATION OF CHLOROPHENOXY AND OTHER ACIDIC HERBICIDE RESIDUES IN-GROUND WATER BY CAPILLARY GAS-CHROMATOGRAPHY OF THEIR ALKYL ESTERS FORMED BY RAPID DERIVATIZATION USING VARIOUS CHLOROFORMATES

A simple method for the determination of several chlorophenoxy acid and other acidic herbicides as methyl, ethyl and butyl esters by means of capillary gas chromatography is described. Derivatization with chloroformates (methyl, ethyl or butyl chloroformate) to give the corresponding methyl, ethyl or butyl esters of the pesticides tested can easily be achieved. Fifteen chlorophenoxy acid and seven other acidic herbicides can easily be deter-mined by gas chromatography with electron-capture or mass spectrometric detection at the relevant residue levels of 100 ng/l in water samples. Recoveries were determined with spiked tap and ground water samples at 50, 100 and 200 ng/l using solid-phase extraction with RP-18 material. Nineteen out of the 22 herbicides could be found with a recovery of more than 75% and the remaining three herbicides could be extracted with a recovery of more than 50%. Tentative confirmation can be achieved by simply esterifying two aliquots of the sample extracts with two different chloroformates.