Characterization of 14C Terminal Residues in Rice Plants Treated with 14C Ring-Labeled Benthiocarb

HONG-MING CHENG AND DENG-FWU HWANG

Department of Marine Food Science, National Taiwan Ocean University Keelung, Taiwan, R.O.C

ABSTRACT

   The terminal 14C residues in rice treated with 14C ring-labeled benthiocarb were characterized. Rice was treated at 5 lb/acre, then grown to maturity. Straw and grain were harvested and analyzed for 14C. The total 14C in the straw and the grain was 2.0 and 0.3 ppm, respectively, calculated as benthiocarb. No (less than 0.01 ppm) parent compound or metabolites containing the intact thiocarbamate moiety were found in either the straw or the grain. Approximately 0.25 ppm 4-chlorobenzoic acid (0.41 ppm 14C calculated as benthiocarb) was isolated from straw as bound, conjugated and/or free metabolites. Two other major 14C metabolites (0.33 ppm), both containing carboxylic acid and the 4-chlorobenzylthio moieties in the molecules, were partially identified. Approximately 0.02 ppm 4-chlorobenzyl methyl sulfone was found in the grain.

Key words : Thiocarbamate herbicide, Degradation products of benthiocarb