Analysis of Method to Determine Pesticide Residues in Tea Using Gas Chromatography -Mass Spectrometry

Abstract

Sri Lanka is renowned for its high quality tea and is the 3rd biggest tea producing country globally. Diseases, insects, nematode .pest damages and weeds affect the crops at different stages of the plant and times of the year. Therefore Pesticides are used in tea plantation to increase efficiency, quality and productivity of the crop. A small amount of these pesticides can remain in the processed tea and caused acute or chronic toxicity to humans. To ensure that food safety is maintained, the residue level of the pesticides including their derivatives is tested. If the residue level of the pesticide is exceeded the maximum allowed residual limits,the tea consignment is rejected by the export market causing a great damage to the prevailing world famous name of the tea industry. Therefore analysis of method to determine pesticide residues level of tea is extremely important before they are been exported. Therefore we focused on four main pesticide residues (Carbofuran, Carbosulfan, Diazinon,Dimethoate) in tea and extract the residues into organic solvents (Dichloromethane, Acetone,Acetonitrile, Lightpetroleum). Then the extract was cleaned up using florisil and alumina columns. The cleaned extract was dried and redissolved in Hexane. The purified extract was analyzed by Gas chromatography-Mass spectrometry. The Diazinon extraction method was qualitatively satisfied for black tea, green tea and flavored tea .The recovery percentage in black tea was 68.15% .Minimum detection limit was .Olppm. Extraction method for Carbofuran, Carbosulfan and Dimethoate was qualitatively satisfied for high concentrations (over 50ppm) Therefore the extraction method used for Carbofuran, Carbosulfan and Dimethoate must be further develop qualitatively and quantitatively for low concentrations. A better extraction method or used method must be developed to minimize the loss during extraction of Diazinon.