Contamination of drinking water supplies by arsenic is a world-wide problem. Total arsenic measurements are commonly used to investigate and regulate arsenic in water, but it is well understood that arsenic occurs in several chemical forms, and these exhibit different toxicities. It is problematic to use laboratory-based speciation techniques to assess exposure as it has been suggested that the distribution of species is not stable during transport in some types of samples. A method was developed in this study for the on-site speciation of the most toxic dissolved arsenic species: As (III), As (V), monomethylarsonic acid (MMA) and dimethylarsenic acid (DMA). Development criteria included ease of use under field conditions, applicable at levels of concern for drinking water, and analytical performance.The approach is based on selective retention of arsenic species on specific ion-exchange chromatography cartridges followed by selective elution and quantification using graphite furnace atomic absorption spectroscopy. Water samples can be delivered to a set of three cartridges using either syringes or peristaltic pumps. Species distribution is stable at this point, and the cartridges can be transported to the laboratory for elution and quantitative analysis. A set of ten replicate spiked samples of each compound, having concentrations between 1 and 60 µg/L, were analyzed. Arsenic recoveries ranged from 78-112 % and relative standard deviations were generally below 10%. Resolution between species was shown to be outstanding, with the only limitation being that the capacity for As (V) was limited to approximately 50 µg/L. This could be easily remedied by changes in either cartridge design, or the extraction procedure. Recoveries were similar for two spiked hard groundwater samples indicating that dissolved minerals are not likely to be problematic. These results suggest that this methodology can be use for analysis of the four primary arsenic species of concern in drinking water supplies.

中文翻译：

---

水中砷形态的现场部署方法。

砷对饮用水供应的污染是一个世界性的问题。总砷测量通常用于调查和调节水中的砷，但众所周知，砷以多种化学形式存在，并且表现出不同的毒性。使用基于实验室的物种形成技术来评估暴露是有问题的，因为有人认为某些类型样品在运输过程中的物种分布不稳定。本研究开发了一种方法，用于现场分析毒性最强的溶解砷物质：As (III)、As (V)、单甲基砷酸 (MMA) 和二甲基砷酸 (DMA)。开发标准包括在现场条件下的易用性、适用于饮用水的关注水平以及分析性能。该方法基于在特定离子交换色谱柱上选择性保留砷物种，然后使用石墨炉原子吸收光谱进行选择性洗脱和定量。可以使用注射器或蠕动泵将水样输送到一组三个小柱中。此时物种分布稳定，可将小柱运至实验室进行洗脱和定量分析。分析了浓度在 1 到 60 µg/L 之间的每种化合物的 10 个重复加标样品。砷回收率范围为 78-112%，相对标准偏差通常低于 10%。物种之间的分辨率非常出色，唯一的限制是 As (V) 的容量限制在大约 50 µg/L。这可以通过更改墨盒设计或提取程序轻松解决。两个加标的硬地下水样品的回收率相似，表明溶解的矿物质不太可能有问题。这些结果表明，该方法可用于分析饮用水供应中的四种主要砷种类。