Assessment of aflatoxin and pesticide residue in cowpea (Vigna unguiculata L. Walp.) from North Central Nigeria

Abstract

Cowpea is a major staple food crop which serves as a source of protein for many Nigerians. Its production and preservation involve the application of pesticides to ensure optimum yield and prevent storage losses. The study evaluated aflatoxin and pesticide residues present in Cowpea grains obtained from retailers in major markets in six States of North Central and the Federal Capital Territory Abuja, Nigeria. The quantitative detection of pesticide residue was conducted through the use of Gas chromatography fitted with Electron Capture Detector (GC-ECD). Aflatoxin (AfB₁, AfB₂, AfG₁ and AfG₂) analysis was conducted by the use of thin layer chromatography (TLC). Twenty-three pesticide residues including organochlorine insecticides, dichlorodiphenyltrichloroethane (DDT), dichlorodiphenyldichloroethylene (DDE), dichlorodiphenyldichloroethane (DDD), fungicide (Etridiazole, chloroneb), herbicide (Simazine, atrazine) were detected in cowpea samples. Dichlorodiphenyldichloroethylene (DDE) was present in 95% of the samples while endosulfan sulfate and endosulfan II were detected in 85% of the cowpea samples. Endrin aldehyde, DDT and DDD were the least detected. Pesticides residues in cowpea grains tested ranged from 72.67 mg kg^{- 1} in samples from Kogi State to 159.67 mg kg^-1 in samples from Plateau State which were above the allowable limits of 20 mg kg^-1. Aflatoxin was below detectable limits in all the cowpea samples analyzed. The high amount of pesticide residues in the cowpea samples poses health hazards to unsuspecting cowpea consumers.