Analysis of low-level 129I in brine using accelerator mass spectrometry
Analysis of low-level 129I in brine using accelerator mass spectrometry
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DOI：
10.1007/s10967-013-2915-y
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发表时间：
2014-01
影响因子：
1.6
通讯作者：
Ning Chen;X. Hou;Weijian Zhou;Yukun Fan;Qi Liu
中科院分区：
文献类型：
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作者：
Ning Chen;X. Hou;Weijian Zhou;Yukun Fan;Qi Liu
本文介绍了一种改进的溶剂萃取分离盐水样品中碘的方法。必须去除盐水样品中的油，以避免溶剂萃取过程中出现第三相，并提高碘的化学产率。残留在水相中的少量油首先通过相分离除去，所述相分离是基于它们的不溶性通过充分沉降，然后通过纤维素过滤器过滤，在所述过滤器上吸附并除去油。除油后碘的萃取回收率可达90%以上。在酸化前加入亚硫酸氢钠作为有效的还原剂，以避免样品中碘在pH 1-2下与碘酸盐反应生成I2而损失碘，然后调节pH值至1-2，将碘酸盐还原为碘化物，再将碘化物氧化为I2，用溶剂萃取法分离全部无机碘。作为前核时代的样品，卤水中的129 I/127 I比值通常比现在地表环境样品低两个数量级以上，因此在处理过程中防止仪器的交叉污染和记忆效应对获得可靠的结果至关重要，而程序空白的监控对129 I的分析质量至关重要。测定了卤水样品和碘试剂程序空白中的129 I/127 I同位素比值，（1.9-2.7）× 10 - 13和2.08 × 10 - 13，比西安环境样品低3-4个数量级，程序空白结果与过去3年的实验结果处于同一水平。这表明在我们的方法中没有观察到污染。
An improved solvent extraction procedure for iodine separation from brine samples has been applied at Xi’an Accelerator Mass Spectrometry (AMS) center. Oil in the brine sample has to be removed to avoid appearance of the third phase during solvent extraction and to improve the chemical yield of iodine. The small amount of oil remained in the water phase was first removed by phase separation through settling down sufficiently based on their immiscibility, and then by filtration through a cellulose filter, on which oil was absorbed and removed. After oil removed, extraction recovery of iodine could achieve more than 90 %. The sodium bisulfite as an effective reductant should be added before acidification to avoid loss of iodine by formation of I2in sample via reaction of iodate and iodide at pH 1–2, and then pH was adjusted to 1–2 to reduce the iodate to iodide followed by oxidation of iodide to I2and solvent extraction to separate all inorganic iodine. As a pre-nuclear era sample,129I/127I ratio in brine is normally more than two orders of magnitude lower than that in present surface environmental samples, so prevention of cross-contamination and memory effect in apparatus during processing procedure are very critical for obtaining reliable results, and monitoring the procedure blank is very important for analytical quality of129I. The129I/127I isotopic ratio in the brine samples and procedure blank of iodine reagents were measured to be (1.9–2.7) × 10−13and 2.08 × 10−13, respectively, 3–4 orders of magnitudes lower than that in environmental samples in Xi’an, and the result of procedure blank is in the same level as the previous experiments in past 3 years, indicating contamination is not observed in our method.