A rapid GC method of monitoring Mesurol (4-(methylthio)-3,5-xylyl-N-methyl carbamate) and its sulfoxide and sulfone metabolites and their persistence in lowbush blueberries

A facile analytical procedure was developed for determining Mesurol (4-(methylthio)-3,5-xylyl-N-methyl carbamate) and its oxidation products in blueberries. It involved blending with acetone, partition with chloroform and derivatization with trifluoroacetic anhydride and quantitation by gas chromatography/flame photometric detector (GC/FPD). The method showed good recoveries for Mesurol and its sulfoxide at the 0.1 ppm level and Mesurol sulfone at the 0.3 ppm level with a 25 g sample. It was applied to monitor levels of the insecticide and its oxidation products on field-treated blueberries. The sensitivity of the method may be increased 5-fold by the inclusion of a clean-up step. The optimal conditions for the detection of Mesurol TFA by the modified Bendix sulphur/phosphorus emission detector operating in the sulphur mode required an oxygen/hydrogen ratio of 0.38, for a column flow of 60 ml/min. The minimum detectable amounts of the TFA derivatives of Mesurol, its sulfoxide and sulfone were calculated as 1.3, 2.3 and 5.8 X 10(-11) g/sec, respectively.