An inter-laboratory evaluation of new multi-element reference materials for atmospheric particulate matter measurements

Eight institutes using 12 different instruments analyzed newly developed multi-element reference materials (RM) for atmospheric particulate matter (PM) measurements. These RM have the potential to fill a gap in the currently available quality assurance resources for element analysis of PM samples such as X-ray fluorescence and inductively-coupled plasma mass spectrometry. This study evaluates the performance of these new RM generated by the University of California, Davis. The methodological challenge was to determine the reference loadings on the RM. Gravimetry is the most robust method to determine the sample deposit mass but cannot be used for these RM because some solution components are volatile and result in unpredictable total mass loadings on the RM. Instead of using gravimetry, a single well-measured element, along with the assumption that the relative mass fractions in the solutions were maintained in the aerosol deposited on the filters, was used to determine the reference loadings on the RM. This assumption appears to be valid for most elements in the solutions; notable exceptions include volatile species such as chlorine and bromine. Results from the 12 different instruments in the inter-laboratory evaluation agreed very well with the reference loadings (adjusted R2 > 0.9 and slope between 0.7 and 1.3) for 17 of the 28 elements. In many cases, one or two instruments did not meet the performance criteria, which points to individual instrument calibration problems. For the 11 elements that did not perform as well, development work continues, and this intercomparison helped identify and fix a source of contamination in the system used to create the RM. Copyright © 2019 American Association for Aerosol Research

8家机构采用12台不同型号的仪器，对专为大气颗粒物（Particulate Matter，PM）检测开发的新型多元素标准参考物质（Reference Material，RM）开展了分析工作。此类标准参考物质有望填补当前PM样品元素分析领域质量保障资源的空白，适配的分析方法包括X射线荧光光谱法与电感耦合等离子体质谱法。本研究针对加利福尼亚大学戴维斯分校（University of California, Davis）制备的该新型标准参考物质的性能开展了评估。本次研究的方法学难点在于确定标准参考物质的参考负载量。重量分析法是测定样品沉积质量的最可靠方法，但由于部分溶液组分具有挥发性，会使标准参考物质上的总质量负载出现不可预测的波动，因此无法用于此类标准参考物质的检测。为此，研究团队未采用重量分析法，而是选取一种准确定量的元素，并结合“溶液中的相对质量分数可保留在沉积至滤膜的气溶胶中”这一假设，来推算标准参考物质的参考负载量。该假设对于溶液中的绝大多数元素均适用，但氯、溴等挥发性物种属于显著例外情况。在本次实验室间比对评估中，12台仪器针对28种元素中的17种所得的检测结果与参考负载量吻合度极高，校正决定系数（adjusted R²）均大于0.9，斜率介于0.7至1.3之间。在多数检测场景中，有1至2台仪器未能达到性能判定标准，这表明部分仪器存在校准问题。针对剩余11种表现未达标的元素，相关研发工作仍在推进；而本次实验室间比对也帮助团队发现并解决了标准参考物质制备系统中的一处污染源。© 2019 美国气溶胶研究协会（American Association for Aerosol Research）版权所有