Fast determination of demeton-S-methylsulfoxide (Metasystox R) in blood plasma

An HPLC method for the detection of demeton-S-methyl-sulfoxide (Metasystox R) in human plasma was developed. DSMSO was extracted by passing the acidified plasma sample through an Extrelut 3 column and eluted from the column with dichloromethane. An aliquot of the extract was injected onto the HPLC nitrile reversed-phase column. The mobile phase was a solution of 3% acetonitrile in 0.01M phosphoric acid. The eluent was monitored at 215 nm. With this method, plasma concentrations between 0.5 and 50 mg/L were determined. Within this range, the concentration-response relation was linear (r = 0.9991). The within-run and between-run coefficients of variation were concentration dependent, with maximal values less than 10%. The analysis took about 45 minutes.