Spectrophotometric and TLC detection reagent for the insecticides dichlorvos (DDVP) and diptrex (Trichlorfon), and their metabolites, in biological tissues

Abstract

Summary A new reagent has been developed for spectrophotometric quantification and thin-layer chromatographic (TLC) detection of the insecticides dichlorvos (DDVP) and diptrex (Trichlorfon), after extraction from biological tissues, blood, and commercial formulations. The reagent is prepared from strong alkali, for example 10% sodium hydroxide, and 0.5% aqueous sodium sulfide solution. The color system obeys the Beer–Lambert law at λ = 401 nm in the concentration range 2–100 μg mL–1. TLC plates coated with a 0.25-mm layer of silica gel G were loaded with microgram quantities of dichlorvos and diptrex standards (from solution) and ethereal extracts of biological samples, for example stomach–intestine, liver–spleen–kidney, and blood. The plate was developed with hexane–acetone, 8 + 2, as mobile phase, dried in air, and sprayed with the reagent. Red spots of dichlorvos and diptrex were obtained at R F 0.26 and 0.42 respectively. The sensitivity of the reagent is ~20 μg for both dichlorvos and diptrex. The reagent is based on the well-known ‘Ogston Reaction’ in which dichloroacetaldehyde produced by alkaline hydrolysis of dichlorvos and diptrex reacts with sodium sulfide giving yellow spots which turn wine red after some time. Dichloroacetaldehyde is reported to be the major metabolite of dichlorvos and diptrex. Other carbamate, organophosphorus, organochlorine, and synthetic pyrethroid insecticides and other components of biological tissue extracts do not interface with the reagent.