铬（Cr）是目前正在接受美国环境保护局（USEPA）审查的成分之一，作为第6部分 年度监管审查流程。加利福尼亚州使用总铬作为筛查指标 合规性监测中的六价铬（Cr-6）。在这些领域有一个重要问题 是Cr和Cr-6测量的准确度。几家供应商已经开发了混合 引入反应气体以过滤干扰（如氩碳）的腔室 （弧）。在引入样品之前，惰性气体与感兴趣的元素发生反应 在ICPMS方法中，如200.8（例如Perkin Elmer Dynamic）中，将其转换为主四极 反应细胞（DRC）。DRC的使用显著提高了总Cr的准确性 测量并对报告的大量合规性数据提出疑问 不使用这种技术。 该研究分析了500多个地下水、瓶装水、饮用水和饮用水样本 美国环境保护局方法218.6测定的Cr-6原水和最后两种方法的总Cr为200.8 4年。这 允许直接评估Cr-6的典型百分比和 影响测量准确度的因素。已经证明，总铬 由于碳的干扰，ICPM可能会出现误报，即使样品 在分析之前，在酸化条件下保存，以去除CO2。然而，假阴性 虽然已经有很好的文件记录，但它们并没有被很好地理解。 在2001年和2002年，观察到一种现象，即许多样本似乎含有更多的蛋白质 Cr-6比总Cr高，这在物理上是不可能的。当时假设总Cr ICPMS的测量结果可能出现假阴性，这是由于 仪器对三价和六价铬的反应，因为添加过氧化氢增加 当通过ICPMS测量时，六价铬的回收率。Park等人（2004年）假设 负片是由于与样品中的铁相互作用，在低pH条件下选择性地去除铬 2002年，采用质量校正法进行了200.8倍的Cr测量 酸化后的碳，以消除ArC的假阳性。然而 碳的修正本质上是经验的，并非在所有碳范围内都是精确的。在里面 2003年，该研究开始使用DRC代替直接碳校正。2002年，近50%的 这些总Cr的测量值小于Cr-6浓度，其值高达 200%. 相比之下，在2003年，使用DRC模式，只有不到20%的样本具有明显的“过剩” Cr-6”，几乎所有这些都在ICPMS和IC测量的分析误差范围内。 对几个特定样本矩阵的研究也支持了准确性的提高 由于使用了刚果民主共和国。 然而，铁的存在可能是防止 准确分析Cr，使用DRC似乎可以克服大多数矩阵干扰 饮用水源。包括4个参考文献、表格、图表。

Chromium (Cr) is one of the constituents currently undergoing review by the U.S. Environmental Protection Agency (USEPA) as part of the 6 year regulatory review process. California uses total Cr as a screening measurement for hexavalent chromium (Cr-6) in compliance monitoring. One issue of importance in these areas is the accuracy of Cr and Cr-6 measurements. Several vendors have developed mixing chambers where reaction gasses are introduced to filter out interferences such as Argon-Carbon (ArC). The inert gas reacts with the element of interest prior to the introduction of the sample into the main quadrupole in ICPMS methods such as 200.8 (e.g. Perkin Elmer Dynamic Reaction Cell-DRC). Use of the DRC significantly improves accuracy of total Cr measurements and raises questions about much reported compliance data that was reported without using this technology. The study analyzed in excess of 500 samples of groundwater, bottled water, potable water, and raw surface water for both Cr-6 by USEPA Method 218.6 and total Cr by 200.8 for each of the last 4 years. This has allowed direct assessments of both the typical percentage of Cr-6 and an assessment of factors affecting the accuracy of measurements. It has been demonstrated that total Cr by ICPMS can be subject to false positives due to interference from carbon, even when samples are held under acidified conditions before analysis to remove CO2. However, false negatives are not as well understood, although they have been well documented. In 2001 and 2002, a phenomenon was observed whereby many samples appeared to have more Cr-6 than total Cr, a physical impossibility. At the time it was hypothesized that total Cr measurements by ICPMS were subject to a false negative as a result of possible differences in instrument response to trivalent and hexavalent Cr, because addition of peroxide increased recovery of hexavalent Cr when measured by ICPMS. Park et al (2004) postulated that false negatives are due to interaction with iron in samples, selectively removing Cr at low pH. In 2002, Cr measurements by 200.8 were made using a mass correction for carbon following acidification, in order to eliminate false positives from ArC. However, corrections for carbon are empirical by nature and not accurate over all ranges of carbon. In 2003 the study began using the DRC in lieu of direct carbon correction. In 2002, nearly 50% of these measurements of total Cr were less than the Cr-6 concentrations, with values as high as 200%. In contrast, in 2003, using DRC mode, less than 20% of samples had apparent "excess Cr-6" and almost all of these were within the analytical error of ICPMS and IC measurements. Studies on several specific sample matrices have also supported the improvements in accuracy due to use of the DRC. While the presence of iron may be a compounding factor in preventing accurate analysis of Cr, use of the DRC appears to overcome most matrix interferences in drinking water sources. Includes 4 references, table, figures.