THIN-LAYER CHROMATOGRAPHIC-SEPARATION AND IDENTIFICATION OF CARBOFURAN AND 2 CARBAMATE METABOLITES AND THEIR DINITROPHENYL ETHERS

Residues of carbofuran [insecticide] and its 2 carbamate metabolites in fortified fresh water, a sandy loam soil and plant tissue were extracted with HCI, partitioned into methylene chloride and cleaned up on deactivated Florisil. Aliquots of extracts were chromatographed on silica gel G and GF plates and carbofuran, 3-hydroxycarbofuran and 3-ketocarbofuran were hydrolyzed into their 7-phenols with KOH spray. Spots were visualized with p-nitrobenzenediazonium fluoroborate or 2,6-dibromobenzoquinone-4-chloroimine. The characteristic color of spots before and after spraying with KOH or with either chromogenic reagent in ordinary light and under UV light helped in identification and differentiation of the compounds. As low as 0.05 ppm in water and 0.2 ppm in soil or strawberry, lettuce, carrots, peas and potatoes was detected. 3-Hydroxycarbofuran in the remaining extracts was converted into 3-ethoxycarbofuran and the compounds were converted into their dinitrophenols and chromatographed on silica gel GF. Good seperation of compounds was obtained but the limit of detection was 0.1 ppm in water and 0.3 ppm in soil and plant tissue. The procedures were applicable to field-treated rutabaga samples and useful in identity confirmation.