A new method for thioarsenate preservation in iron-rich waters by solid phase extraction.
A new method for thioarsenate preservation in iron-rich waters by solid phase extraction.
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DOI：
10.1016/j.watres.2016.07.008
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发表时间：
2016-10
期刊：
影响因子：
12.8
通讯作者：
M. Ullrich;V. Misiari;B. Planer-Friedrich
中科院分区：
文献类型：
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作者：
M. Ullrich;V. Misiari;B. Planer-Friedrich
为了保存用于砷形态分析的富铁样品，通常添加无机酸或EDTA以防止铁的氧化和沉淀。然而，当存在硫化物并且可能形成硫代砷酸盐（[HAsVS-IInO 4-n]2-，n = 1-4）时，由于硫化砷沉淀或人为形态变化，这些方法不适用。本文研究了一种在硫化物存在下通过固相萃取（SPE）分离阴离子砷和阳离子铁的新方法。将含有亚砷酸盐、砷酸盐、单硫代砷酸盐和三硫代砷酸盐的合成溶液通过阴离子交换树脂AG 2-X8，之后将树脂洗涤、洗脱，并通过IC-ICP-MS分析每个步骤的形态。发现砷酸盐、单硫代砷酸盐和三硫代砷酸盐在树脂上的保留率分别为96.8 ± 0.2%、98.8 ± 0.2%和99.6 ± 0.3%。分别阳离子铁（90 μM Fe（II））未保留（0.4 ± 0.2%）。不带电荷的亚砷酸盐在不存在硫化物的情况下通过树脂，而47.3%的亚砷酸盐通过结合到有机树脂结构的硫醇基团以10倍硫化物过量保留。用3 × 15 mL 0.5 M水杨酸盐洗脱（包括浸泡时间）可定量回收所有保留物质。用来自捷克矿泉的富含铁的天然沃茨水测试树脂上保留物质的稳定性。砷酸盐、一硫代砷酸盐、二硫代砷酸盐和三硫代砷酸盐成功地与铁分离，并在6 d后回收。因此，SPE提出了一个可行的答案，在铁和硫化物的存在下保存砷的问题。
In order to preserve iron-rich samples for arsenic speciation analysis, mineral acids or EDTA are typically added to prevent oxidation and precipitation of iron. However, when sulfide is present, and thioarsenates ([HAsVS−IInO4−n]2−, n = 1–4) can form, these methods are unsuitable due to arsenic sulfide precipitation or artifact speciation changes. Here, a new method based on separating the anionic arsenic species from cationic iron in the presence of sulfide via solid phase extraction (SPE) has been investigated. Synthetic solutions containing arsenite, arsenate, monothioarsenate, and trithioarsenate were passed through the anion-exchange resin AG2-X8, after which the resin was washed, eluted, and speciation of each step analyzed by IC-ICP-MS. Retention on the resin of 96.8 ± 0.2%, 98.8 ± 0.2%, and 99.6 ± 0.3% was found for arsenate, monothioarsenate, and trithioarsenate, respectively. Cationic iron (90 μM Fe(II)) was not retained (0.4 ± 0.2%). Uncharged arsenite passed through the resin in the absence of sulfide, while 47.3% of arsenite were retained at tenfold sulfide excess via thiol groups binding to the organic resin structure. Elution with 3 × 15 mL of 0.5 M salicylate, including a soak time, resulted in quantitative recovery of all retained species. Stability of the retained species on the resin was tested with iron-rich, natural waters from a Czech mineral spring. Arsenate, monothioarsenate, dithioarsenate, and trithioarsenate were successfully separated from iron and recovered after 6 d. Thus, SPE presents a viable answer to the problem of preserving arsenic in the presence of both iron and sulfide.