SIMULTANEOUS DETERMINATION OF VAMIDOTHION AND ITS OXIDATION METABOLITES IN POTATOES AND APPLES BY GAS-CHROMATOGRAPHY

A method for simultaneous determination of vamidothion (V0) and its ox idation metabolites vamidothion sulphoxide (V1) and vamidothion sulpho ne (V2) in potatoes and apples has been developed. Fifty grams of a sa mple was homogenized and extracted with acetone followed by evaporatio n to remove the acetone. To the residual aqueous solution, a 10% sodiu m chloride solution was added, and the coextractives were eliminated b y washing the aqueous solution with 10% ethyl acetate in hexane. Then, VO, VI, and V2 were extracted from the aqueous solution using dichlom methane. The organic layer was evaporated to dryness and filled up to 2 ml with ethyl acetate. Two microliters of the extract were injected into gas chromatograph-mass spectrometer set for selected ion monitori ng. The column used was a CBP-1 capillary column (0.2 mm inside diamet er x 15 m, 0.25 mum film thickness). Gas chromatographic conditions we re investigated in detail and only nonpolar capillary columns gave sat isfactory results. The retention time of undecomposed V1 has been repo rted for the first time. The recoveries for the fortified potatoes and apples were 93-109% for VO, 62-108% for VI, and 64-89% for V2, when t hey were fortified at levels of 0.01-5.0 ppm. Detection limits were 0. 01, 0.2, and 0.05 ppm for V0, V1, and V2, respectively.