A thermo extraction–UV/Vis spectrophotometric method for total iodine quantification in soils and sediments
A thermo extraction–UV/Vis spectrophotometric method for total iodine quantification in soils and sediments
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DOI：
10.1007/s00216-007-1621-4
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发表时间：
2007-10
影响因子：
4.3
通讯作者：
Benjamin Gilfedder;Frederik Althoff;M. Petri;Harald Biester
中科院分区：
文献类型：
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作者：
Benjamin Gilfedder;Frederik Althoff;M. Petri;Harald Biester
由于碘在酸性条件下的挥发性，土壤和沉积物中的碘是一种很难分析的元素。传统上，它是使用中子活化分析技术来量化的，不幸的是，这需要进入核反应堆。本文介绍了一种简单的固相碘分析方法，即在1000℃下热萃取固相碘，然后用紫外/可见光度法定量。样品在氧气中燃烧，并被困在Milli-Q水中。然后用As3+-Ce4+分光光度法定量，据此碘化物催化As3+氧化为As5+，Ce4+还原为Ce3+。对三种标准物质进行了分析，回收率为97-113%，相对标准偏差为5%。且检出限小于50 ng绝对碘，置信限为95%。当应用于部署在康斯坦茨湖的沉积物陷阱中的富含碳酸盐的样品时，我们发现碘含量非常低(0.8-2 mg kg−1)。尽管浓度较低，但该方法的精密度始终优于5%的RSD。然而，对于来自黑森林湖泊的有机和富碘沉积物(有机碳含量为20-30%)，该方法需要通过增加氧气流量和缩短燃烧时间进行轻微改进。采用改进后的方法，相对标准偏差小于5%。
Iodine in soils and sediments is a difficult element to analyze due to its volatility in acidic conditions. Traditionally it has been quantified using neutron activation analysis techniques, which, unfortunately, requires access to a nuclear reactor. We present here a simple method for solid-phase iodine analysis by thermo extraction at 1000°C and quantification by UV/Vis photometry. Samples are combusted in an oxygen stream and trapped in Milli-Q water. The extracts are then quantified by an As3+–Ce4+spectrometric method whereby iodide catalyzes the oxidation of As3+to As5+and reduction of Ce4+to Ce3+. Three standard reference materials were analyzed with excellent recoveries (97–113%) and RSDs (<5%). Moreover, the detection limit was less than 50 ng absolute iodine with a confidence limit of 95%. When applied to carbonate-rich samples from sediment traps deployed in Lake Constance we found very low iodine levels (0.8–2 mg kg−1). Despite the low concentrations, the precision of the method was consistently better than 5% RSD. However, the method needed to be slightly modified for organic and iodine-rich sediments (20–30% organic carbon) from a lake in the Black Forest by increasing the oxygen flow rate and decreasing the combustion time. Using the modified method we were able to achieve RSDs lower than 5%.