Mass discrimination correction in multiple-collector plasma source mass spectrometry: an example using Cu and Zn isotopes
Mass discrimination correction in multiple-collector plasma source mass spectrometry: an example using Cu and Zn isotopes
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DOI：
10.1039/b315853e
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发表时间：
2004-01-01
影响因子：
3.4
通讯作者：
Vance, D
中科院分区：
文献类型：
--
作者：
Archer, C;Vance, D
多接收器磁区 ICP-MS 提供了使用分析物以外的元素（掺杂剂）的参考同位素比率来应用仪器质量辨别校正的可能性。许多注意力集中在使用这种方法进行铊掺杂剂的铅同位素分析上，并且该技术也已应用于铜锌同位素分析。掺杂方法最成功的应用已经在掺杂剂和分析物同位素比率之间建立了经验质量偏差关系，但这通常必须在单个分析过程中完成。群体歧视的会话内变化不足通常会导致对这些关系的约束不佳。此外，对于 Tl-Pb 系统，样品和标准是否表现出相同的关系存在一些疑问。在这里，我们表明，对于 Cu-Zn 系统，对先前方法的两项改进可以实现未知物的精确同位素比。首先，向混合 Cu-Zn 标准溶液中添加 Sr 会产生质量偏差的极大变化，从而更好地限制分析物和掺杂剂之间的经验质量偏差关系。其次，我们表明，不充分的化学反应，特别是基质 Fe 和 Ti 的低效去除，严重影响了样品的 Cu-Zn 同位素分析，但通过清洁的化学反应，具有复杂基质的样品显然会产生与标准相似的 Cu 和 Zn 同位素之间的质量辨别关系。我们还记录了以前未报道的 Cu-Zn 同位素分析方面：(1) Cu-Zn 质量偏差关系主要取决于溶液的 Cu/Zn 比率； (2) 对于具有去溶剂化膜的引入系统，标准品的行为变化很大，可能是由于溶液中 Cu 氧化态的变化，并且可以通过使标准品通过用于纯化样品的离子交换程序来克服这一问题。最后，我们记录了化学分离和质谱技术，这些技术允许对比以前实现的小数量级的样品进行同位素分析，并报告 95% 置信水平下 delta(66)Zn = 0.20 +/- 0.09% (n = 12) 和 delta(65)Cu = 0.07 +/- 0.08% (n = 6) 的 BCR-1 玄武岩标准值。
Multiple-collector magnetic sector ICP-MS affords the possibility of applying instrumental mass discrimination corrections using a reference isotope ratio of an element (dopant) other than the analyte. Much attention has focused on the use of this approach for lead isotope analysis using a thallium dopant and the technique has also been applied to copper-zinc isotope analysis. The most successful applications of the doping approach have established empirical mass bias relationships between dopant and analyte isotope ratios but this often has to be done for single analytical sessions. Insufficient intra-session variation in mass discrimination often leads to poor constraints on these relationships. Moreover, with the Tl-Pb system there is some doubt over whether samples and standards exhibit the same relationship. Here we show that for the Cu-Zn system, two improvements on previous approaches lead to precise and accurate isotope ratios for unknowns. Firstly, addition of Sr to mixed Cu-Zn standard solutions generates extreme variation in mass bias so that empirical mass bias relationships between analyte and dopant are much better constrained. Secondly, we show that inadequate chemistry, specifically the inefficient removal of matrix Fe and Ti, seriously compromises the Cu-Zn isotope analysis of samples but that with clean chemistry, samples with complex matrices demonstrably yield similar mass discrimination relationships between Cu and Zn isotopes to standards. We also document previously unreported aspects of Cu-Zn isotope analysis: (1) that Cu - Zn mass bias relationships depend critically on the Cu/Zn ratio of the solution; (2) that for an introduction system with a desolvating membrane, the behaviour of standards is highly variable, perhaps due to variations in the oxidation state of Cu in the solution, and that this can be overcome by the passage of standards through the ion exchange procedure used to purify samples. Finally, we document chemical separation and mass spectrometric techniques that permit the isotopic analysis of order of magnitude smaller samples than previously achieved and report values for BCR-1 basalt standard of delta(66)Zn = 0.20 +/- 0.09% (n = 12) and delta(65)Cu = 0.07 +/- 0.08% (n = 6) at the 95% confidence level.