Determination of acibenzolar-S-methyl and its degradation product in agricultural products by HPLC

A method was developed for analysis of acibenzolar-S-methyl (benzo[1,2,3]thiodiazole-7 carbothioic acid S-methyl ester, BTH) and its decomposition product, benzo[1,2,3]thiodiazole-7-carboxylic acid (BTC), in grains by HPLC and LC/MS. BTH and BTC were extracted from grains with 0.1 mol/L phosphate buffer (pH 8.0) and acetone. BTH was extracted from the acetone extract (adjusted to pH 7.5 similar to 8.5) with diethylether-n-hexane (1 : 1). The remaining acetone extract was adjusted to < pH 3, and BTC was extracted with diethylether-n-hexane (1:1). The BTH extract was cleaned up on Florisil column after having been defatted by n-hexane-acetonitrile partition. The BTC extract was directly cleaned up on a Florisil column. BTH and BTC were determined by HPLC with UV or LC/MS (Scan or SIM). Recoveries of both compounds from rice, wheat and corn spiked at the level of 0.1 mug/g were in the range of 76.8 similar to 86.7% (standard deviation was 0.3 similar to 2.7%). The limits of detection were 0.003 mug/g (BTH) and 0.008 mug/g (BTC) by HPLC/UV.