Margolis Sam A, Angelo Jacob B
National Institute of Standards and Technology, Gaithersburg, MD 20899-8392, USA.
Anal Bioanal Chem. 2002 Oct;374(3):505-12. doi: 10.1007/s00216-002-1493-6. Epub 2002 Sep 10.
The precision and bias of the coulometric Karl Fischer ASTM method D1533-00 have been assessed in a collaborative ASTM round robin program for a group of 34 laboratories. The test materials used in this study included water saturated 1-octanol (WSO), water saturated 1-butanol (WSB), and a series of new and used transformer oil samples. Fundamental systematic biases have been demonstrated in the accuracy of the measurement of water in the WSO, WSB, and transformer oil samples. The systematic bias in the measurement of the WSO and WSB standards indicates that for some laboratories either the instruments were not accurate or the quantity of the standard was not measured accurately. A second type of systematic bias consisted of measurement errors associated with the selection of the Karl Fischer solvent that was used with each instrument, and this was superimposed upon the error in the measurement of the water in the standards. Using the statistical calculation method ASTM D 6300 the repeatability and reproducibility for water in transformer oil were found to be 7 mg/kg and 14 mg/kg respectively. The method detection limit of water was 8 mg/kg oil. The method bias was estimated based on the National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 2890, WSO, since no suitable reference material for water in transformer oil was available for this study.
在一项由美国材料与试验协会（ASTM）组织的、有34个实验室参与的协作循环试验项目中，对电量卡尔费休法（ASTM方法D1533 - 00）的精密度和偏差进行了评估。本研究中使用的测试材料包括水饱和的1 - 辛醇（WSO）、水饱和的1 - 丁醇（WSB）以及一系列新的和使用过的变压器油样品。在WSO、WSB和变压器油样品水分测量的准确性方面已证明存在基本的系统偏差。WSO和WSB标准测量中的系统偏差表明，对于一些实验室来说，要么仪器不准确，要么标准品的量没有准确测量。第二种系统偏差包括与每台仪器所使用的卡尔费休溶剂选择相关的测量误差，并且这种误差叠加在标准品水分测量的误差之上。使用ASTM D 6300统计计算方法，发现变压器油中水分的重复性和再现性分别为7 mg/kg和14 mg/kg。该方法对水的检测限为8 mg/kg油。由于本研究没有适用于变压器油中水的参考物质，因此基于美国国家标准与技术研究院（NIST）标准参考物质（SRM）2890，即WSO，来估计该方法的偏差。
