Study On The Matrix Of Testing Organophosphorus Pesticides Residue In Tea

Nowadays, the developed countries raise the tea export standards, which made the MRL of pesticide residues lower and lower. The developed countries set up technical barriers which based on food safety. It severely threaten the export tea market and made the food safe more importance. The organophosphorus pesticide is used widely in China. It's the effective way to control organophosphate pesticide residues and to protect the tea safety of import and export which based on. the development of the fast, reliable and sensitive organic phosphorus pesticide residues detection technology. A new fast, reliable and sensitive method for the determination of multiple pesticide residues in tea using GC was developed. The method consists with the analysis of pesticide residues in development. Accurate quantification and identification of susceptive analysis can be seriously affected due to matrix-induced enhancement or suppression effect that commonly encountered in gas chromatographic analysis of organophosphorus pesticides in tea.49 organophosphorus pesticides were extracted and cleaned up using acetone and Florisol from tea samples by matrix solid-phase dispersion extraction, detected by GC. The protectants improves the peak shape of some polar organophosphorus pesticides such as methamidophos, trichlorfon, alephate, omethoate etc. and compensate the matrix effect efficiently . It also enhanced the sensitivity and reducing the limit of detection successfully. Good linear and lower limits of detection were obtained , the linear range are between 0.01～1.00mg/L , correlation coefficients are better than 0.99, and the detection limits is between 0.0003～0.0096mg/kg.All compounds spiked in tea have mean recoveries of 75.7%～105.2%(0.32mg/kg level)and the relative standard deviation(RSD) values are between 0.2%～10.2%. The method has all parameters the test needs, which can monitor the organophosphorus pesticides in tea.It was demonstrated that applying protectants could provide a more accurate quantity in gas chromatography analysis, thus increase reliability of test. Effects of 3 compounds used as protectants on compensation for matrix effect are evaluated in tea matrix and comparison with matrix-matched standard are made. The matrix induced error for most pesticide has been shown to be avoided by adding A(20mg/mL) and C (10mg/ml) before injection, especially for methamidophos,acephate, trichlorfon, omethoate, dicrotophos, phosphamindon etc; beside it reduced the limit of detection.After researching for the matrix of 4 major components in tea, the result indicated that organophosphorus pesticides were impacted by the tea components in a certain degree. The majority of effects performed enhancing effects. Among the 4 major components of tea , Most organophosphorus pesticides show some extent matrix-induced response enhancement in the matrix of caffeine and theanine. Some organophosphorus pesticides show some extent matrix-induced response lower in the matrix of tea polyphenol. Among the 49 organophosphorus pesticides which researched , they depended different components of tea such as Dichlorphos, methamidophos, alephate, omethoate, phosphamindon, paraoxon etc., but some are stabile in different components of tea such as diazinon, monocrotophos, chlopynifo, pirimiphos-methyl, parathion, phosfolan etc. Most organophosphorus pesticides represented stronger matrix-induced response enhancement in the matrix of caffeine than in other 3 components. From this , the substance which caused the matrix-induced response enhancement was more content in caffeine .