Identification and Quantification of Organophosphate and Carbamate Pesticide Residues in Tomatoes, Carrots, Sorrel and Spinachusing the Quechers Method and Detection by GC-MS

Abstract

The Concentrations of organ phosphorus and carbamate pesticide residues were analysed in spinach, tomatoes, carrots and sorrel grown at Dagachi farming areas along River Galma of Zaria in Kaduna State, Nigeria. Samples collection and preparationwere carried out using standard procedures. The concentrations of all the pesticides in the samples were analysed using quick easy cheap effective rugged and safe (QuEChERS) multi- residue extraction and clean up techniques, followed by gas chromatography – mass spectrometry (GC – MS) method of analysis. The most commonly detected organ phosphorus pesticide residues in the entire sample analysed are dichlorvos, mevinfos, diazinon, malathion, chlorpyrifos, ethion, isofenphos and azinphos-methyl. The detected carbamates are the carbaryl and carbofenthion. The linearity (r2 ≥ 0.9999) for the pesticides was good over the concentration range from 0.05 – 1.00 ppm. The results of the detected organ phosphorus in the samples show that, malathion presents the highest value in carrot with value of 0.522 mg/kg and lowest value of azinphos- methyl in both carrot and spinach with value of 0.006 mg/kg. Also, chlorpyrifos, 0.099 mg/kg, 0.274 mg/kg, 0.122 mg/kg in spinach, carrot, and sorrel respectively detected were also very high. Other detected organ phosphorus was within the MRLs in all the samples anaysed. However, other organ phosphorus pesticides were detected at a very low concentration. Carbaryl were detected in tomatoes, carrot and sorrel samples with a value of 0.003 mg/kg, 0.003 mg/kg and 0.002 mg/kg respectively. The concentrations of all the organophosphorus pesticides in the samples in this research work were observed to be at alarming levels, much higher than the maximum residue limits(MRLs) by the Codex 2009 (WHO and FAO). Therefore, to reduce this risk, sensitization of farmers to better pesticide safety practices and the need for continuous pesticide residue monitoring is highly recommended. Finally, there is a need for the relevant agency to strictly control the importation, sale, use and disposal of these toxic chemicals.