Analysis of some carbamate and urea herbicides in foods by gas-liquid chromatography after alkylation.

The quantitative analysis of a number of carbamate and urea herbicides in selected foods was examined. The compounds were extracted from the crops with ethanol which was subsequently partitioned between water and chloroform. The organic extract was evaporated to dryness and alkylated with sodium hydride-methyl iodide. The products were extracted with hexane and directly analyzed by gas chromatography. Detection of the derivatives was accomplished with a Coulson electrolytic conductivity detector in the nitrogen mode. No column cleanup was required for any of the samples down to the 0.01 ppm level. Detection limits were about 0.005 ppm. Recoveries were usually 60-100% depending upon the herbicide. Confirmation of the chlorine-containing herbicides was carried out with the Coulson in the chloride (reductive) mode.