Joint Research Centre, Institute for Reference Materials and Measurements, European Commission, 2440, Geel, Belgium.
Anal Bioanal Chem. 2010 Jan;396(1):503-10. doi: 10.1007/s00216-009-3198-6. Epub 2009 Oct 12.
A proficiency test to assess the capabilities of laboratories to determine melamine in a milk powder and a baking mix, representing starch-containing foods like bread and biscuits, was carried out in January 2009. The need for such an interlaboratory comparison arose from a health scare in China about melamine-tainted powdered milk in the second half of 2008. Laboratories in 31 countries, including Australia, China, India, Japan, New Zealand and the USA, and 21 of the 27 Member States of the European Union participated and reported back 114 results for the milk powder and 112 for the baking mix test materials. The reported results were compared to reference values determined by exact-matching double isotope dilution mass spectrometry. The so-determined assigned values were 10.0 +/- 0.6 mg/kg melamine in the milk powder and 3.18 +/- 0.17 mg/kg melamine in the baking mix. A coverage factor k of 2 was applied to calculate the expanded uncertainties. Three quarters of all reported results for both materials had associated z scores which were satisfactory (z <or= |2|). Of the reported results, 90% was accompanied by a measurement uncertainty statement, and the majority of the measurement uncertainty ranges were reasonable. A number of laboratories were found to underestimate their measurement uncertainties. Methods that involved the use of stable-isotope-labelled melamine were shown to be clearly advantageous with regard to the accuracy of the results. However, no significant influence by other method parameters could be identified.
2009 年 1 月进行了一项能力验证测试，以评估各实验室测定奶粉和烘焙混合物（如面包和饼干等含淀粉食品）中三聚氰胺的能力。之所以需要开展这项实验室间比对，是因为 2008 年下半年中国发生了受三聚氰胺污染的毒奶粉事件。来自澳大利亚、中国、印度、日本、新西兰和美国等 31 个国家以及欧盟 27 个成员国中的 21 个成员国的实验室参与了此次测试，并报告了 114 个奶粉测试材料和 112 个烘焙混合物测试材料的结果。报告的结果与通过精确匹配双同位素稀释质谱法确定的参考值进行了比较。由此确定的赋值为奶粉中三聚氰胺含量为 10.0 +/- 0.6 mg/kg，烘焙混合物中三聚氰胺含量为 3.18 +/- 0.17 mg/kg。应用覆盖因子 k = 2 计算扩展不确定度。两种材料的所有报告结果中，有四分之三的 z 分数都令人满意（z <or= |2|）。在报告的结果中，有 90%附有测量不确定度声明，并且大部分测量不确定度范围都合理。发现一些实验室低估了它们的测量不确定度。使用稳定同位素标记的三聚氰胺的方法在结果准确性方面显然具有优势。但是，没有发现其他方法参数有显著影响。
