Behavior of N-methylcarbamate pesticides during refinement processing of edible oils

Abstract

The following N-methylcarbamate pesticides, aldicarb, aldicarb sulfoxide, aldicarb sulfone, oxamyl, methomyl, thiodicarb, propoxur, carbofuran, carbosulfan, benfuracarb, bendiocarb, carbaryl, fenobcarb and furathiocarb, were added to soybean oil, each at 5 mg/kg(5 ppm), followed by degumming, alkali refining, bleaching and deodorization for oil refinement. Residual pesticide content in each case was determined immediately after refining. DEGUMMING: Aldicarb, aldicarb sulfoxide, aldicarb sulfone, oxamyl, thiodicarb, carbosulfan, benfuracarb were each found to decrease by as much as 70% by H(3)PO(4) treatment, this being less than 26% noted for the other pesticides. With hot water treatment, the decrease in any one pesticide was less than 52%. ALKALI REFINING: The rate of decrease varied with the pesticide, ranging from 8% to 100%. 200%NaOH were effectively brought about pesticide removal, compared to 125%NaOH. BLEACHING: Aldicarb, aldicarb sulfoxide, aldicarb sulfone, oxamyl, methomyl, thiodicarb, carbosulfan, benfuracarb, bendiocarb and furathiocarb each decreased by more than 80% with activated clay containing activated charcoal. Carbaryl decreased remarkably by this clay. Pesticide removal in all cases was at less than 30%. DEODORIZATION: 40% Furathiocarb, 14% carbosulfan, 11% benfuracarb and 3% carbofuran could still be detected subsequent to deodorization at 260 degrees C while all other pesticide amounts were too small to permit quantitative detection. Degumming with H(3)PO(4) and bleaching with activated clay caused the conversion of carbosulfan and benfuracarb into carbofuran. Carbofuran and furathiocarb may thus possibly still remain in the oil following the above 4 refinement processes.