Stacey P R, Wright M D
Health and Safety Laboratory, Broad Lane, Sheffield, UK S3 7HQ.
J Environ Monit. 2001 Aug;3(4):425-31. doi: 10.1039/b101351n.
The Workplace Analysis Scheme for Proficiency (WASP) is a proficiency testing scheme for the analysis of occupational hygiene and environmental air samples and is operated in the UK by the Health and Safety Laboratory. Since 1997, WASP has offered samples of benzene, toluene and m-xylene, at environmental levels on Tenax, and has about 35 laboratories participating, mostly from industry, local government and consultancy organisations in the UK. The results reported cover the first 10 rounds of the environmental analytes (1997-1999) and demonstrate the important role of proficiency testing in assessing the quality of laboratory performance. Estimates are obtained for within-laboratory precision and the total variability at each analyte level. The estimates of within-laboratory precision suggest that laboratories have more difficulty analysing toluene and m-xylene than benzene. Linear relationships for the reproducibility relative standard deviation (RSDT) with loading level are evident for the analytes at occupational levels. At environmental levels, the relationship between loading level and reproducibility is much less well defined. The standard deviation for the proficiency testing assessment for all three analytes at the environmental level is 14%, as derived from the benzene data. Expanded uncertainty estimates (k = 1.96), for the analysis of samples since the scheme started, are obtained from the average total variance, and are 27% for benzene, 39% for toluene and 36% for m-xylene. Although the linear trend of performance against round number was not significant at the 95% level of confidence (p = 0.23 for benzene, p = 0.3 for toluene and p = 0.32 for m-xylene), there was a general improvement in RSDT from 26-34% to about 8-13% 10 rounds later. Currently, for a laboratory to meet one of the data quality objectives in the Ambient Air Directive (indicative measurement of benzene, expanded uncertainty +/- 30% or less), it would have to achieve a level of analytical performance to satisfy the category 1 (best performance) limit of better than +/- 8.8%. In the last proficiency testing round, discussed in this paper, only 58% of laboratories obtained performance scores that indicated that they were able to consistently achieve this level of performance.
工作场所熟练度分析方案（WASP）是一项用于职业卫生和环境空气样本分析的熟练度测试方案，由英国健康与安全实验室负责运营。自1997年以来，WASP提供了环境水平下Tenax管上苯、甲苯和间二甲苯的样本，约有35个实验室参与，其中大部分来自英国的工业、地方政府和咨询机构。报告的结果涵盖了环境分析物的前10轮测试（1997 - 1999年），并证明了熟练度测试在评估实验室性能质量方面的重要作用。获得了各分析物水平下实验室内部精密度和总变异性的估计值。实验室内部精密度的估计表明，与苯相比，实验室在分析甲苯和间二甲苯时遇到的困难更大。职业水平下分析物的再现性相对标准偏差（RSDT）与负载水平之间存在明显的线性关系。在环境水平下，负载水平与再现性之间的关系则不太明确。根据苯的数据得出，环境水平下所有三种分析物的熟练度测试评估标准偏差为14%。自该方案启动以来，根据平均总方差获得了样本分析的扩展不确定度估计值（k = 1.96），苯为27%，甲苯为39%，间二甲苯为36%。尽管在95%置信水平下，性能随轮次的线性趋势不显著（苯的p = 0.23，甲苯的p = 0.3，间二甲苯的p = 0.32），但10轮后RSDT总体上从26 - 34%提高到了约8 - 13%。目前，对于一个实验室来说，要满足《环境空气指令》中的一项数据质量目标（苯的指示性测量，扩展不确定度±30%或更低），其分析性能水平必须达到优于±8.8%的1类（最佳性能）限值。在本文讨论的最后一轮熟练度测试中，只有58%的实验室获得的性能分数表明它们能够始终如一地达到这一性能水平。
