A multiclass, multiresidue analytical method for pesticides in water

A procedure is reported for the multiclass, multiresidue analysis of pesticides in water. Compounds are extracted from water with methylene chloride, and the extract is concentrated by an evaporative technique utilizing reduced pressure and low temperature. Compounds are segregated into groups using a column of partially deactivated silica gel and sequential elution with four different solvent systems. Carbamate residues, converted to their 2,4-dinitrophenyl ether derivatives, are gas chromatographed via electron capture detection as are the parent compounds of the organohalogen compounds. Organophosphorus compounds are determined by gas chromatography using a flame photometric detector. Recovery studies were conducted on 42 halogenated compounds, 38 organophosphorus compounds, and 7 carbamates. Fifty-eight of 87 compounds tested produced recoveries in excess of 80%; another 13 compounds yielded recoveries exceeding 60%, while the recoveries on the remaining 16 compounds fell below 60%.