Studies On Simple Chemical Testing Methods Of Pyreturoid Pesticide Residues In Tea

Nowadays, pesticides, especially pyrethroid pesticide, are widely used in tea production. However, it could largely enrich in tea and do hurm to people directly. The main available methods of pesticide residues detection are gas chromatography assay and high performance liquid chromatography analysis. Due to the inconvenience, they could not be popularly applied in tea producing area. As a result, it is necessary to develop a useful method to detect the pesticide residues accurately. Our studies showed that one method based on the chemical constituents of tea could detect the pyrethroid pesticides fleetly. The main results are as follows:To extract the pesticide residues in tea efficiently, acetonitrile was used as solvent to distill the pesticide residues under the ultrasonic for 15 min after drying the tea leaf rapidly at 110℃.TLC (Thin Layer Chromatography) analysis which could detect the deltamethrin residues qualitatively as well as semi-quantitatively was performed without strict purification processes.The pyrethroid pesticide residues in tea could produce CN ions by alkali degradation. According to the Color Reaction of Prussian Blue with CN ions, the pyrethroid residues could be determined directly.The pyrethroid pesticide residues could also be accurately determined by the Color Reaction of DNPH(dinitrophenylhydrazine) with aldehydes and ketones, following a series processes of extraction, purification and the degradation of alkali. Otherwise, the Color Reaction of Isonicotinic acid with pyrazolone combined with a specific pre-treatment method were applied to detect the cyano pyrethroid residues.The hydrolysis of cyano pyrethroid could produced CN ions then turn into HCN which was collected for detection.