New thin-layer chromatographic method for detection of synthetic pyrethroids containing a nitrile group

A new chromogenic reagent was developed for the detection of synthetic pyrethroids containing a hydrolysable nitrile group i.e., fenvalerate, cypermethrin and fenpropathrin. These synthetic pyrethroids, on alkaline hydrolysis, yield a cyanohydrin derivative which gives HCN and a corresponding aldehyde. This liberated HCN reduces 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyltetrazolium chloride (INT) to formazan, a pink product, in the presence of phenazonium methosulfate (PMS). The organochlorine, organophosphorus and carbamate do not interfere in the determination. The limit of detection is about 1 mu g.