基于气相色谱质谱法测定茶叶中哒螨灵等9种农药残留量的测量不确定度评定

李俊; 蔡滔; 代虹镜; 苏美丞; 祝愿; 王震

doi:10.13386/j.issn1002-0306.2021090073

基于气相色谱质谱法测定茶叶中哒螨灵等9种农药残留量的测量不确定度评定

Evaluation of Measurement Uncertainty for the Determination of Pyridaben and Other Nine Pesticide Residues in Tea by Gas Chromatography-Mass Spectrometry

摘要

摘要: 目的：评定气相色谱质谱法测定茶叶中哒螨灵等9种农药含量的不确定度。方法：本研究基于气相色谱质谱法，结合内标定量，采用两个不同检测方法对茶叶中哒螨灵等9种农药的残留进行了不确定度的详细评定，对标准物质的配制、样品称量、样品提取、净化、测量等实验过程引入的不确定度进行评定和分析。结果：分析评定合成不确定度过程，可知不确定度贡献主要来自标准曲线拟合（不确定度1.45%~7.93%）、样品添加回收率（方法1不确定度2.64%~3.54%，方法2不确定度1.62%~5.89%）和标准溶液配制（不确定度2.46%），对实验结果的影响较大，其次是样品测量重复性，在极低测量浓度时（不确定度为0.5%~2.56%），影响最为明显。结论：选择合适的前处理方法，严格控制样品前处理各步骤，使用合适的标准曲线浓度点范围，在定量软件中调整标准曲线浓度点的权重，能够获得更好的拟合结果，测量结果如出现阳性检出时，样品需要复测3次以上计算平均值才能得到较可靠的结果。

Abstract: Objective: To evaluate the uncertainty of determination of nine pesticides in tea by gas chromatography and mass spectrometry (GC-MS). Methods: The uncertainties of nine pesticide residues in tea were evaluated by GC-MS combined with internal standard quantitative method. Five evaluation components, including pesticide standards preparation, sample weighing, extraction, purification and detection were studied. Results: The main uncertainty in the determination of pesticides came from the fitting process of standard curve (u_rel(R)=1.45%~7.93%), sample recovery (u_rel(Q)^a=2.64%~3.54%, u_rel(Q)^b=1.62%~5.89%) and standard solution preparation (u_rel=2.46%), then the repetition of the sample measurement (u_rel(A)=0.5%~2.56%), especially at the extremely low concentration. Conclusion: For the reliable results, it is important to choose the accurate sample preparation, the concentration range of standard curve. And when the results indicates positive, reassays should be done in triplicate.