Detection of Dichlorvos Residue in Cowpea Grains, Six Months after Application Using High Performance Liquid Chromatography

Abstract

In Kano State Nigeria, especially at the famous Dawanau grains market, dichlorvos (DDVP: 2, 2-dichlorovinyl dimethyl phosphate), which is a synthetic organophosphate insecticide is being widely used against stored insect pests of cowpea grains by traders and merchants alike. High Performance Liquid Chromatography (HPLC) screening using commercially available brand of such an organophosphate insecticide was carried out in a Chemistry Laboratory at Bayero University Kano in 2014. This was aimed at determining the presence or absence of the insecticide in the treated and untreated grains of cowpea before, day one and six months after application. The analysis was carried out using an Agilent 1260 Quadpump HPLC, equipped with diode array detector, autosampler and thermostetted column compartment. The result was processed using Agilent Chemstation software. Dichlorvos detection was achieved at 214 nm, while the overlaid chromatograms suggested the presence of DDVP: 2, 2-dichlorovinyl dimethyl phosphate in the test sample relative to the chromatogram of the standard commercial sample at a retention time of 2.163 and 2.283 minutes, respectively. The peak of the target compound was visibly not present in the control chromatogram at the stated retention time. In conclusion, detection of dichlorvos in grains six months after application highlights among others, the dangers and/or disadvantages associated with the use of the chemicals for the protection of stored cowpea grains against insect pests especially by the personnel lacking requisite knowledge on the appropriate ways of handling/application of such synthetic products for both human and environmental safety.