Determination of Pesticide Residues in Organic and Conventional Exotic Vegetables

Pesticides are used to protect crops from diseases and pests. Their application in agriculture has been in existence since ancient times to date. They have also been used in growing vegetables especially exotic vegetables that are more prone to pests and diseases. There have been concerns over indiscriminate use of pesticides by farmers to grow vegetables especially for local markets since there are no guidelines on Maximum residue levels. This study was done to determine the concentration of cypermethrin and lambda-cyhalothrin pesticide residues in Collard (Brassica oleracea var. acephala) Tomatoes (Solanum lycopersicum) and swiss chard (Beta vulgaris subsp. cicla). The samples included both organic and conventional vegetables that use chemical pesticides. Experimental study design was used which involved laboratory analysis of the samples. Sample extraction was done using AOAC official method 2007.01 known as Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method. The method involves use of Acetonitrile, sodium chloride and anhydrous magnesium sulphate for extraction. Clean-up was done using dispersive-solid phase extraction method using Primary-Secondary Amine and anhydrous magnesium sulphate. Residues analysis was done using Reverse-phase High Performance Liquid chromatography. Peak areas of the curves were calculated using Motic Images plus 2.0 and data analysis was done using SPSS 22. Recovery rates of pesticide ranged from 87.78% to 97.93% for cypermethrin and 90.65% to 95.72% for lambda-cyhalothrin. The results indicated that organic vegetable samples had pesticide residues below detectable levels while conventional vegetable samples had levels ranging from 2.495mg/kg to 0.238mg/kg for cypermethrin and 0.352mg/kg to 0.119mg/kg for lambda-cyhalothrin. The residues of both pesticides were above the recommended, this is likely to cause negative health effects such as uncoordination, whole-body tremors and seizures. This indicates that conventional vegetable consumers are exposed to pesticide residues. Farmers should strictly adhere to good agricultural practice to reduce pesticide residues