气相色谱法测定黄瓜中丙溴磷农药残留量的测量不确定度评定

为评定检测方法NY/T 761-2008处理的黄瓜中丙溴磷农药残留检测结果的测量不确定度,找出对测量不确定度影响大的因素,规范实验操作,提高检测结果的准确性,本文通过外部加标,建立数学模型,从量器使用、标准工作液配制、重复性测量等各个分量进行评定。结果表明,丙溴磷残留量0.45 mg/kg,其扩展标准不确定度0.04 mg/kg,对测量不确定度有显著贡献的有三个方面:标准物质纯度的相对标准不确定度2%;使用6次移液器产生的相对标准不确定度2.661%;标准曲线拟合的相对标准不确定度1.615%。因此,在检测中,建议购买纯度在98.6%以上的标准溶液,做好贮存和期间核查;在配制标准工作液时,减少使用移液器的频次或使用更精密的量器且定期做好校准;按时做好测量仪器的检定和期间核查。

Measurement Uncertainty of Determination of Profenofos (PFF) Residues in Cucumber Evaluated by Gas Chromatography (GC)

To evaluate the measurement uncertainty of the analysis results of PFF pesticide residues in cucumber extracted by NY/T 761-2008, find out the factors that have great influence on the measurement uncertainty, the experimental operation was standardized and the accuracy of the detection results was improved. A mathematical model was established through external reference material addition to evaluate the measurement uncertainty from the used of equipment, the prepared standard working fluid, and the repeatability measurement. The results showed that residual amount of PFF was 0.45 mg/kg, and the expanded standard uncertainty was 0.04 mg/kg. There were three aspects that contributed significantly to the measurement uncertainty:The relative standard uncertainty of the purity of the reference material was 2%, the relative standard uncertainty was 2.661% that pipettes was used for six times, and the relative standard uncertainty of the fitting of the standard curve was 1.615%. Therefore, in the detection, it was recommended to purchase reference material with purity of more than 98.6%, do well in storage and period verification, reduce frequency of using pipette, and use more precise measuring device when standard working fluid was prepared. Calibration of measuring device should do regularly, and the testing instruments should be verify during the test period.