Department of Occupational and Environmental Medicine, University of Milan and Fondazione IRCCS Ospedale Maggiore Policlinico, Mangiagalli e Regina Elena, Via S. Barnaba, 8-20122 Milan, Italy.
J Chromatogr B Analyt Technol Biomed Life Sci. 2010 Oct 1;878(27):2534-40. doi: 10.1016/j.jchromb.2009.11.045. Epub 2009 Dec 3.
Biological monitoring of low level exposure to pollutants is a very challenging analytical activity, and the quality of results is difficult to assess, especially when a certified reference material is unavailable. The aim of this work was to evaluate the reliability of the assays used to measure urinary benzene (Benz-U) and S-phenylmercapturic acid (SPMA), by applying an internal quality control protocol. Urine spot samples from 705 subjects who were either members of the general urban population, gasoline station attendants, or refinery plant workers were assayed for Benz-U and SPMA, using GC/MS and LC/MS/MS, with quantification limits of 15 ng/L and 0.10 μg/L. The median Benz-U concentration was 263 ng/L (60-2789 ng/L, 5th-95th percentile), and the median SPMA concentration was 0.19 μg/L (<0.1-2.5 μg/L, 5th-95th percentile). Linearity of both assays was good, but a less-than-proportional response was found for SPMA concentrations below 1 μg/L. Between-run precision and accuracy for Benz-U concentration determination were assessed using quality controls at 120 ng/L and 1000 ng/L and were 10.3% and 4.8%, and 104.8% and 98.9%, respectively; while the precision and accuracy for SPMA concentration determination at 0.3 μg/L, 2.5 μg/L, and 20 μg/L were 40.3%, 6.2%, and 6.2%, and 48.3%, 96.3%, and 98.8%, respectively. Precision, estimated using duplicates of unknown samples, was 13.4% for Benz-U and 26.5% for SPMA analyses. Control charts for the means of the slope of the linear calibration curve of Benz-U showed good stability of the means over a five-year period. For SPMA, a two-laboratory comparison revealed acceptable agreement between ln-transformed data pairs, with a slope of the linear regression of 0.863 (confidence interval 0.774-0.952), null intercept, and a Pearson's r value of 0.844. Reliable results were obtained for Benz-U analyses over the entire concentration range, and for high and medium SPMA levels. However, the determination of SPMA concentrations at levels close to the limit of quantification was less reliable.
生物监测低水平污染物暴露是一项极具挑战性的分析活动，其结果质量难以评估，尤其是在缺乏认证参考物质的情况下。本研究旨在通过应用内部质量控制方案，评估用于测量尿液中苯（Benz-U）和 S-苯巯基尿酸（SPMA）的检测方法的可靠性。使用 GC/MS 和 LC/MS/MS 对来自普通城市居民、加油站工作人员和炼油厂工人的 705 名个体的尿斑样本进行 Benz-U 和 SPMA 分析，定量限分别为 15ng/L 和 0.10μg/L。Benz-U 的中位数浓度为 263ng/L（60-2789ng/L，5-95 百分位数），SPMA 的中位数浓度为 0.19μg/L（<0.1-2.5μg/L，5-95 百分位数）。两种检测方法的线性均良好，但 SPMA 浓度低于 1μg/L 时呈非比例响应。使用 120ng/L 和 1000ng/L 的质控品评估 Benz-U 浓度测定的批间精密度和准确度，结果分别为 10.3%和 4.8%，104.8%和 98.9%；而 SPMA 浓度测定的批间精密度和准确度在 0.3μg/L、2.5μg/L 和 20μg/L 时分别为 40.3%、6.2%和 6.2%，48.3%、96.3%和 98.8%。使用未知样本的重复样本估计精密度，Benz-U 分析的精密度为 13.4%，SPMA 分析的精密度为 26.5%。Benz-U 线性校准曲线斜率均值的控制图显示，5 年内均值稳定性良好。对于 SPMA，两实验室比较显示 ln 转换数据对之间具有可接受的一致性，线性回归的斜率为 0.863（置信区间 0.774-0.952），零截距，Pearson's r 值为 0.844。Benz-U 分析在整个浓度范围内以及高浓度和中浓度 SPMA 水平均获得可靠结果。然而，在接近定量限的水平上测定 SPMA 浓度的可靠性较低。
