Comparative profile of glyphosate residues in cowpea grains sold in the municipal and satellite towns of Abuja, Nigeria

The profile of glyphosate residues in cowpea grains sold in the Federal Capital Territory Abuja (FCT), Nigeria was assessed using high performance liquid chromatography.
Methods: Thirty-three cowpea grains samples of red and white morphotype were collected from some selected markets within the FCT, Abuja. Analytical methods on the pulverized cowpea grains included dispersive liquid-liquid microextraction using acetonitrile/water (55:45) as mobile phase, sample clean up and their quantification by HPLC/UV as described by AOAC - QuEChERS method.
Results: The percentage recoveries of the GLY pesticide standard were found to be acceptable at 90.01-101% with limits of detection pesticides standard were 0.011mgkg-1 and limits of quantification from 0.022 mgkg-1 and regression correlation coefficient (r2) of 0.987332.
The results showed that the mean concentration of glyphosate in the cowpea grains ranged from 0.11-44.32 ± 0.001 mgkg_1 with a mean glyphosate concentration of 6.280 mgkg-1 was detected. Six samples representing 18.18% of the samples collected violated WHO/FAO CODEX standard of 15.0 mgkg-1. Comparative studies between municipal and satellite markets revealed that GLY concentration residue was highest and lowest in K’WB (44.32 mg/kg) and K’IB (0.11 mg/kg) respectively while values recorded for Acceptable Daily Intake (ADI) for all the samples were within an acceptable limit of 0.1mgkg-1. Heath risk index values were <1 suggesting that the consumer populations were not at risk.
Conclusion: The high profile of glyphosate residue in cowpea grains from Karimu and Abaji Area Councils of the FCT is of great concern and needed to be further investigated.