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Double-spike data reduction in the presence of isotopic anomalies
Journal of Analytical Atomic Spectrometry ( IF 3.1 ) Pub Date : 2017-08-08 00:00:00 , DOI: 10.1039/c7ja00187h
Justin Y. Hu 1, 2, 3, 4, 5 , Nicolas Dauphas 1, 2, 3, 4, 5
Affiliation  

The double-spike technique is one of the most robust and commonly used methods for high precision isotopic mass fractionation analyses by either TIMS or MC-ICPMS. It involves measuring the isotopic compositions of the pure sample, as well as a mixture of the sample and a double-spike made of an artificial mixture of isotopes. If isotopic variations follow the laws of mass-dependent fractionation, one does not need to measure the pure sample and a single measurement of the sample–spike mixture is sufficient. This approach is invalid, however, if the isotopic composition of the sample is not related to that of the standard by mass fractionation because nucleosynthetic anomalies are present, the sample is affected by cosmogenic effects, or one or several of its isotopes are produced by the decay of a radioactive parent. Extraterrestrial materials, in particular, often display isotopic anomalies of nucleosynthetic origin that can be troublemakers in double-spike data reduction if not properly accounted for. In the present publication, we derive an analytical equation to calculate the correction that needs to be applied to the isotopic composition if one erroneously assumes that samples and standards are related by the laws of mass dependent fractionation when in reality isotopic anomalies are present (by anomaly, we mean any departure from mass-dependent fractionation). This formula is applied to previous Mo, Ti and Cr isotopic analyses and demonstrated to yield an accurate correction. The newly derived formula also provides a straightforward means of propagating errors arising from the presence of anomalies in the isotopic composition calculated by the double-spike technique.

中文翻译:

同位素异常时双峰数据减少

两次加标技术是通过TIMS或MC-ICPMS进行高精度同位素质量分数分析的最可靠且最常用的方法之一。它涉及测量纯净样品以及样品和由同位素人工混合物制成的双尖峰的混合物的同位素组成。如果同位素变化遵循质量依赖的分级定律,则无需测量纯样品,并且仅测量样品-掺料混合物就足够了。但是,如果由于存在核合成异常而使样品的同位素组成与质量分馏的标准同位素组成无关,则该方法无效,则样品会受到宇宙成因作用的影响,或者其同位素中的一种或几种是由同位素产生的。放射性母体的衰变。地外物质,特别是,经常显示出核合成来源的同位素异常,如果没有适当考虑的话,可能会成为减少双尖峰数据的麻烦制造者。在本出版物中,如果一个人错误地假设样品和标准品存在质量同位素分离定律,而实际上存在同位素异常(通过异常),则我们导出一个分析方程式,以计算需要应用于同位素组成的校正量。 ,则表示不依赖于质量相关的分离。该公式已应用于先前的Mo,Ti和Cr同位素分析,并被证明可以进行准确的校正。新推导的公式还提供了一种传播误差的简单方法,该误差是由双峰技术计算出的同位素组成中存在异常所引起的。通常会显示出核合成来源的同位素异常,如果没有适当考虑的话,可能会成为减少双峰值数据的麻烦制造者。在本出版物中,如果一个人错误地假设样品和标准品存在质量同位素分离定律,而实际上存在同位素异常(通过异常),则我们导出一个分析方程式,以计算需要应用于同位素组成的校正量。 ,则表示不依赖于质量相关的分离。该公式已应用于先前的Mo,Ti和Cr同位素分析,并被证明可以进行准确的校正。新推导的公式还提供了一种传播误差的简单方法,该误差是由双峰技术计算出的同位素组成中存在异常所引起的。通常会显示出核合成来源的同位素异常,如果没有适当考虑的话,可能会成为减少双峰值数据的麻烦制造者。在本出版物中,如果一个人错误地假设样品和标准品存在质量同位素分离定律,而实际上存在同位素异常(通过异常),则我们导出一个分析方程式,以计算需要应用于同位素组成的校正量。 ,则表示不依赖于质量相关的分离。该公式已应用于先前的Mo,Ti和Cr同位素分析,并被证明可以进行准确的校正。新推导的公式还提供了一种传播误差的简单方法,该误差是由双峰技术计算出的同位素组成中存在异常所引起的。
更新日期:2017-09-04
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