Thin layer chromatography of parathion as paraoxon with cholinesterase inhibition detection.

A simple, sensitive, and rapid method is described for the quantitative estimation of ng amounts of parathion (0,0-diethyl 0-p-nitrophenyl phosphorothioate) as paraoxon (0,0-diethyl 0-p-nitrophenyl phosphate) on thin layer chromatograms. Samples tested included cauliflower and paddy grain. Paraoxon is detected by inhibition, using p-nitrobenzenediazonium fluoroborate as the chromogenic reagent. This chromogenic reagent is more sensitive than Fast Blue B or indoxyl acetate; 0.1 ng may be detected and amounts from 5 to 50 ng may be estimated. The method is a viable alternative to GC analysis for parathion.