The Research And Control Of Matrix Effects To Detect The Residues Of Organophosphorus Pesticides In Tea By Gas Chromatography

Tea is a characteristic of agricultural products with the resources advantage and the cultural deposits in the traditional consumption of china,and tea is agricultural exports with much competitive power in the international market.But the pesticide residues exceeding in tea seriously restricted the export in China.Currently,organophosphorus pesticide is the most widely to use and consume in China,about 70% of them has been revealed highest toxicity,some are even forbidden to apply.In this case,the exact qualitative and quantitative analysis of pesticide residues has become the important technical guarantee to regulate the pesticide use.Gas chromatography is one of the main analytic equipment to detect the organophosphorus residues of pesticide in the tea,but most of organophosphorus pesticides measured by gas chromatography showed matrix effect at different degrees,which influence the quantitative accuracy.Nowadays,the domestic research on the matrix effect has been focus on fruits and vegetables,but very little on tea.Therefore,this paper is aimed to study quantitative detection of 12 kinds of organophosphorus pesticides in different tea matrix by gas chromatography,and discuss the calibration matrix matching method to weaken or eliminate the matrix effect.The main work and results are as follows:1.It is compared five kinds of tea matrix for the determination of 12 organophosphorus pesticides at varied pesticides concentration(0.05,0.10,0.20,0.50 ?g/mL).It is found that five kinds of tea matrix of 12 organophosphorus pesticides have different degrees of enhanced or wakened matrix effect,and the extent of matrix effect is associated with the types of tea and pesticides,there was a correlation between concentrations of pesticides and matrix effect.Moreover,different kinds of organophosphorus pesticides in the same tea matrix exist different degrees of matrix effect,and the same kind of organophosphorus pesticides in the different tea also exists different degrees of enhanced or wakened matrix effect,for the same kind of pesticide there is a significant difference among different concentrations.2.Standard solution mixed of 12 organophosphorus pesticide is added to the five kinds of tea as blank samples to prepare recycling samples with the theory concentration at 0.05?0.10?0.50 mg/kg respectively,the analysis of gas chromatography was operated after extraction and purification of samples.Then,adjust the results with standard curve of pure solvent and blank matrix solvent respectively,and compare above corrected results to explore the matrix effect on the determination of three concentrations of 12 organophosphorus pesticides in the tea,which provided experimental evidence for the classification of tea matrix and selection of representative matrix.Test results show that the matrix effect has a great influence with determination of organophosphorus pesticide residues,and the influence extent has a lot to do with the kinds of samples,The corrected method with matrix standard solution is better than solvent standard curve to calculate the linear correlation coefficient and the recovery rate of organophosphorus.This method can eliminate the matrix effect positively and make the test fit the requirement of pesticide residues analysis.It is also a simple,relatively convenient way to significantly improve the accuracy of pesticide residues analysis and meet the needs of routine laboratory detection.Finally,this paper provides evidence to classify the matrix of tea and select the most representative matrix in the same category for organophosphorus pesticide residue analysis.In routine analysis,green tea and oolong tea can be allocated in the same category,oolong tea blank sample matrix can be chosen as the calibration standard solution.Black tea,pu'er tea and baked tea can be allocated in the same category,black tea blank sample matrix can be chosen as the calibration standard solution.For the samples with interference and excess of pesticide residues,quantitative calibration is chosen to manipulate using the standard matrix solution prepared with the same blank matrix.