Precise determination of cadmium isotope fractionation in seawater by double spike MC-ICPMS
Precise determination of cadmium isotope fractionation in seawater by double spike MC-ICPMS
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DOI：
10.1016/j.gca.2006.10.005
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发表时间：
2007-02-01
影响因子：
5
通讯作者：
Rehkaemper, M.
中科院分区：
文献类型：
--
作者：
Ripperger, S.;Rehkaemper, M.
提出了一种精确测定海水中Cd稳定同位素组成的新方法。该方法利用Cd-110-Cd-111双峰，通过柱层析和多收集器电感耦合等离子体质谱进行同位素分析，从海水中分离Cd。作为副产品，它还能产生精确的镉浓度数据。对三种纯Cd参考物质和三种海水样品的重复分析得出的再现性约为+/- 1.0至+/- 1.6 epsilon Cd-114/110 (2 SD)，基于每次消耗约8 ng天然Cd的测量结果（epsilon Cd-114/110是样品的Cd-114/Cd-110同位素比值与标准的偏差，单位为万分之一）。这表明新的双尖峰技术在获取有限尺寸样品的精确数据方面优于已发表的Cd同位素分析方法。另外的实验表明，低至1-5 ng的海水Cd可以分析，精度约为+/- 2至+/- 6 epsilon Cd-114/110 （2 SD）。通过实验确定了海水同位素数据的准确性，其中在无Cd的海水基质中掺杂少量同位素特征良好的Cd。对几个样品的纯化Cd部分进行了重复的质量扫描，进一步证明了没有明显的光谱干扰。从三个海水样品中获得的同位素数据首次揭示了海洋环境中Cd同位素的小而可分解的分馏。北太平洋富镉中间水的同位素组成为epsilon Cd-141/110 = 3.2 +/- 1.0。而大西洋和北冰洋上层水体cd -贫海水的同位素组成分别为epsilon Cd-114/10 = 6.4 +/- 1.1和6.6 +/- 1.6。这些观测结果与同位素效应是由于浮游植物在吸收溶解海水Cd过程中发生的生物分馏作用的解释一致。(c) 2006爱思唯尔公司版权所有。
A new technique has been developed for the accurate and precise determination of the stable Cd isotope composition of seawater. The method utilizes a Cd-110-Cd-111 double spike, and it involves separation of Cd from seawater by column chromatography and isotopic analyses by multiple collector inductively coupled plasma mass spectrometry. As a by-product, it also generates precise Cd concentration data. Repeated analyses of three pure Cd reference materials and three seawater samples yielded reproducibilities of about +/- 1.0 to +/- 1.6 epsilon Cd-114/110 (2 SD), based on measurements that each consumed about similar to 8 ng of natural Cd. (epsilon Cd-114/110 is the deviation of the Cd-114/Cd-110 isotope ratio of a sample from the standard in parts per 10,000). This demonstrates that the new double spike technique is superior to published methods of Cd isotope analyses, with regard to the acquisition of precise data for samples of limited size. Additional experiments showed that as little as 1-5 ng of seawater Cd could be analyzed with a precision of about +/- 2 to +/- 6 epsilon Cd-114/110 (2 SD). The accuracy of the seawater isotope data was ascertained by experiments in which a Cd-free seawater matrix was doped with small quantities of isotopically well-characterized Cd. Repeated mass scans that were carried out on purified Cd fractions of several samples furthermore demonstrated the absence of significant spectral interferences. The isotope data that were acquired for the three seawater samples reveal, for the first time, small but resolvable Cd isotope fractionations in the marine environment. Cadmium-rich intermediate water from the North Pacific was found to have an isotope composition of epsilon Cd-141/110 = 3.2 +/- 1.0. In contrast, Cd-depleted seawater from the upper water column of the Atlantic and Arctic Oceans displayed isotope compositions of epsilon Cd-114/10 = 6.4 +/- 1.1 and 6.6 +/- 1.6, respectively. These observations are in accord with the interpretation that the isotope effects are due to the biological fractionation that occurs during the uptake of dissolved seawater Cd by phytoplankton. (c) 2006 Elsevier Inc. All rights reserved.