气相色谱法测定粮食中4种有机磷农药残留量的不确定度评定

目的 对气相色谱法测定粮食中乐果、杀螟硫磷、对硫磷、马拉硫磷农药残留量的方法进行不确定度评估。方法 依据JJF 1059.1-2012《测量不确定度评定与表示》和JJF 1135-2005《化学分析测量不确定度评定》中有关规定, 建立了用气相色谱法测定粮食中4种有机磷农药残留量的不确定度评估数学模型, 对测定中的不确定度来源进行分析和评估。结果 当粮食中乐果、杀螟硫磷、对硫磷、马拉硫磷的残留量分别为0.10、0.19、0.095、0.093 mg/kg时, 扩展不确定度分别为: 0.01、0.01、0.010、0.006 mg/kg, 4种有机磷残留量分别表示为: (0.10±0.01) mg/kg (k=2)、(0.19±0.02) (k=2)、(0.095±0.006) mg/kg (k=2)、(0.093±0.007) mg/kg (k=2)。 结论 实验过程中的不确定度主要来源于标准物质配制和样品稀释过程, 本评估方法可为气相色谱法检测多组分农药残留量的不确定度评估提供依据。

Uncertainty evaluation of determination of 4 kinds of organophosphorus pesticide residues in grain by gas chromatography

Objective To evaluate the uncertainty of determination of 4 kinds of organophosphorus pesticide including dimethoate, fenitrothion, parathion and malathion in grain by gas chromatography. Methods According to JJF 1059.1-2012 Evaluation and expression of uncertainty in measurement and JJF 1135-2005 Evaluation of uncertainty in chemical analysis measurement, the mathematical model for the evaluation of uncertainty of 4 organophosphorus pesticide residues in grain by gas chromatography was established. Then the main sources of uncertainty were analyzed and evaluated. Results When the residues of dimethoate, fenitrothion, parathion and malathion in grain were 0.10, 0.19, 0.095 and 0.093 mg/kg, the expansion uncertainty were 0.02, 0.04, 0.019 and 0.018 mg/kg, respectively. The 4 kinds of organophosphorus residues were expressed as (0.10±0.01) mg/kg (k=2), (0.19±0.01) mg/kg (k=2), (0.095±0.010) mg/kg (k=2), (0.093±0.006) mg/kg (k=2). Conclusion The uncertainty in the experimental process mainly comes from the preparation of standard substances and sample dilution process. This evaluation method can provide the basis for the uncertainty evaluation of the detection of multi-component pesticide residues by gas chromatography.