Analysis of insecticide residues in cabbage (Brassica oleracea var. Capitata) from three major markets in Kumasi

Cabbage from 3 major markets (Abinchi, Bantama and Sofoline) in Kumasi were screened for organochlorine, organophosphate and pyrethroid insecticide residues. Ninety cabbage heads - 30 from each market – were randomly sampled and analysed at the Pesticide Residues Laboratories of the Ghana Standards Authority, Accra. The analysis was carried out using Multiple Reaction Monitoring by Gas Chromatography-Pulsed Flame Photometric Detector (GC-PFPD), Gas Chromatography-Electron Capture Detector (GC-ECD) and Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) method to detect residues. The limit of detection (LOD) of organochlorine was set at 0.005 mg/kg and that of organophosphate and pyrethroid was set at 0.01 mg/kg. We observed that no organochlorine was present in any of the samples. Only Diazinon was present in the samples from Abinchi and Bantama but at a level (0.003 ± 0.006 mg/kg) below the maximum residue limit (MRL) of 0.01 mg/kg for cabbage. However, there was a multi-residue contamination in samples from the Sofoline market with Diazinon (0.057 ± 0.098 mg/kg), Cypermethrin (0.007 ± 0.012 mg/kg), Fenvalerate (0.010 ± 0.017 mg/kg) and Lambda-cyhalothrin (0.003 ± 0.006 mg/kg). With these, only the Diazinon was found to exceed its established MRL (0.01 mg/kg) and so is more likely to pose danger to consumers health.