Determination of Tetrachloroterephthalic Acid Residues in Tea by Esterification-Gas Chromatography-Mass Spectrometry
To develop a novel method for quantitative analysis of tetrachloroterephthalic acid residues in tea by gas chromatography-mass spectrometry based on esterification of aryl carboxylic acid with alkyl halide.Samples were extracted with acetonitrile,then the extracts were derivated by ethyl iodide and purified by QuEChERS method.The filtrate was evaporated to dryness by nitrogen evaporator and the residues were diluted with ethyl acetate,which was used for gas chromatography-mass spectrometry analysis,and quantified by external standard method.The results indicate that the linear relationship between values of peak area and mass concentration of tetrachloroterephthalic acid was good in the concentration range of 5.0～50.0 ng·mL-1 with the correlation coefficient above 0.999.The limit of detection was 0.000 05 mg·kg-1,and the limit of quantification was 0.000 15 mg·kg-1.At spiked levels of 0.01 mg·kg-1,0.05 mg·kg-1,0.10 mg·kg-1,the average recoveries of spiked samples ranged from 75.3%to 90.2%,with relative standard deviations between 2.5%and 8.7%.This method is easy,and of high recovery rate and good repeatability,and it can be used for the determination of tetrachloroterephthalic acid residues in tea.
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