ROUTINE QUANTITATIVE RESIDUE DETERMINATIONS OF S-[(2-METHOXY-5-OXO-DELTA2-1,3,4-THIADIAZOLIN-4-YL)METHYL]O,O-DIMETHYL PHOSPHORODITHIOATE (SUPRACIDE) AND ITS OXYGEN ANALOG IN FORAGE CROPS

Methods applicable to routine determination of residues of unchanged Supracide, S-[(2-methoxy-5-oxo-Δ-1,3,4-thiadiazolin-4-yl) methyl] O,O-dimethyl phosphorodithioate, and its oxygen analog in forage crops are presented. The unchanged Supracide is determined by microcoulometric gas chromatography with a limit of detectability of 0.05 p.p.m. Extraction is done using petroleum ether and clean-up with aluminum oxide columns. The oxygen analog is detected on thin-layer chromatography plates by fly head cholinesterase inhibition, with a limit of detectability of 0.01 p.p.m. Extraction of the oxygen analog is done using acetone. No clean-up of this extract is needed before application to the thin-layer chromatography plate. Efficacy of the extraction method for weathered residues is discussed. The methods have been used to determine residues resulting from various levels of application of Supracide to forage crops. © 1969, American Chemical Society. All rights reserved.