Quantitative determination of carbaryl in apples, lettuce, and water by densitometry of thin layer chromatograms

A method for the quantitative determination of carbaryl insecticide by in situ densitometry was developed. After separation on silica gel thin layer plates, carbaryl residues were detected by using p-nitrobenzenediazonium fluoborate reagent and quantitated by scanning the resultant blue spots with a fiber optics densitometer and comparing them with standards. The method was applied to water fortified with carbaryl at 8 ppb and apples and lettuce fortified at 0.10 ppm; all recoveries were greater than 89%. The 2 crop extracts were cleaned up by using the AOAC thin layer chromatographic method for visual estimation of carbaryl. Related carbamate insecticides were detected by using the same reagent, and the potential for quantitation was demonstrated.