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Lessons from the NIST micronutrients quality assurance program for vitamin C, 1993 to 2015: sample stability, assay reproducibility, and use of controls to improve comparability
Analytical and Bioanalytical Chemistry ( IF 4.3 ) Pub Date : 2020-11-02 , DOI: 10.1007/s00216-020-03021-9
David L Duewer 1 , Jeanice Brown Thomas 2 , Katherine E Sharpless 3 , Sam A Margolis 4
Affiliation  

Vitamin C is a necessary micronutrient that is involved in many biological processes. In preserved human plasma and serum, vitamin C is most meaningfully analyzed as total ascorbic acid (TAA). From 1993 through 2015, the National Institute of Standards and Technology (NIST) coordinated 40 interlaboratory studies (ILS) devoted to improving the between-participant comparability of TAA measurements. The results from these ILS demonstrate that the concentration of TAA ([TAA]) is stable for at least 20 years in serum diluted 1 + 1 (volume fraction) with 10% mass concentration aqueous metaphosphoric acid (MPA) and stored at −80 °C. The between-participant relative reproducibility precision, expressed as a coefficient of variation (CV), improved from over 16% to under 9% over the course of the studies. Normalization of test samples (i.e., ex post-facto recalibrating the as-submitted results) using participant-prepared serum-free calibration solutions did not improve reproducibility. Normalization to one control sample having a similar serum-based matrix as the test samples improved the CV to 7%; normalization to two such controls reduced the CV to 4%. Multicenter studies that require the highest degree of measurement comparability among the participants should consider calibrating with materials that have a serum-based matrix as similar as possible to that of the samples of interest.



中文翻译:

NIST 维生素 C 微量营养素质量保证计划的经验教训,1993 年至 2015 年:样品稳定性、测定重现性和使用对照来提高可比性

维生素 C 是一种必需的微量营养素,参与许多生物过程。在保存的人血浆和血清中,维生素 C 作为总抗坏血酸 (TAA) 进行分析最有意义。从 1993 年到 2015 年,美国国家标准与技术研究院 (NIST) 协调了 40 项实验室间研究 (ILS),致力于提高 TAA 测量的参与者之间的可比性。这些 ILS 的结果表明,TAA ([TAA]) 的浓度在用 10% 质量浓度的偏磷酸 (MPA) 稀释 1 + 1(体积分数)并在 -80° 下储存的血清中至少可以稳定 20 年C。在研究过程中,参与者之间的相对再现性精度(以变异系数 (CV) 表示)从 16% 以上提高到 9% 以下。测试样本的归一化(即事后重新校准提交的结果)使用参与者准备的无血清校准溶液并没有提高可重复性。标准化为一个具有与测试样品相似的基于血清的基质的对照样品,将 CV 提高到 7%;标准化为两个这样的控制将 CV 降低到 4%。需要参与者之间最高程度的测量可比性的多中心研究应考虑使用具有与感兴趣样本尽可能相似的血清基质的材料进行校准。

更新日期:2020-11-03
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