Sensitive gas-liquid chromatographic method for asulam residues in peaches

The current analytical method for determining residues of the herbicide asulam (methyl (4-amino-benzenesulfonyl) carbamate) is the nonspecific colorimetric procedure based on the coupling reaction of N-1-naphthylethylenediamine with the diazotized amine. A new analytical method for determining the residues of this herbicide and its 2 known major metabolites, acetylasulam and sulfanilamide, in peaches has been developed and evaluated using gas chromatography with an N-P detector. The method is based on the hydrolytic conversion of the parent compound and the known metabolites to the common product sulfanilamide which is then analyzed by gas-liquid chromatography as its per N-methylated derivative. The identity of the derivative has been confirmed by chemical ionization mass spectrometry. The method was tested by using fortified crop extracts and also be analyzing crop treated by post-emergent application of the method is 5 ng and the detection limit in the crop is 0.1 ppm. Recoveries ranged from 70 to 80% from peaches at fortification levels of 1, 5, and 10 ppm. At a fortification level of 0.1 ppm the recovery is 50-60%.