The misuse of dichlorvos (DDVP), an organophosphorus insecticide, resu
lts in many instances of poisoning. This paper describes a new spray r
eagent for selective detection of dichlorvos in biological materials b
y thin-layer chromatography. Dichlorvos in presence of moisture breaks
down to dichloroacetaldehyde which in turn reacts with phenylhydrazin
e hydrochloride to give a yellowish red colour. In acidic media the co
lour is intensified and consequently the sensitivity of detection incr
eases. The reagent is selective for dichlorvos, other organophosphorus
insecticides failed to give a coloured spot. Moreover organochlorine,
carbamate and synthetic pyrethroid insecticides or even constituents
of visceral extracts (amino acids, peptides, proteins etc.) do not int
erfere. The limit of detection is ca 10 mug.