A spray reagent for the detection of pyrethroid insecticides containing a nitrile group by thin-layer chromatography is described. These insecticides on alkaline hydrolysis yield cyanide ion, which in turn reacts with copper(II) acetate and o-tolidine in an acetic acid medium to give a blue colour. Organochlorine, organophosphorus and carbamate insecticides do not interfere. The limit of detection is about 1 microgram.

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The misuse of sulphur-containing organophosphorus insecticides results in many instances of poisoning. This paper describes a spray reagent for their detection in biological materials by thin-layer chromatography. Sulphur-containing organophosphorus insecticides react with acidified potassium iodate liberating free iodine, which in turn reacts with starch solution to give a blue colour. In alkaline media the colour is intensified and consequently the sensitivity of detection increases. There is no interference from other organochloro insecticides or even carbamate insecticides or from the constituents of visceral extracts (amino acids, peptides, proteins, etc). The limit of detection is ca. 1 pg. Keywords : Thin -layer chroma tog rap h y; potassium iodate; sulp h u r-con taining organophosphorus insecticides; b io log ica I mate ria I Paper A7185