双稀释剂法在非传统稳定同位素测定中的应用——以钼同位素为例
The Application of Double Spike in Non-Traditional Stable Isotopes —A Case Study on Mo Isotopes
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摘要: 仪器的质量分馏校正是提高同位素分析数据精度的关键。"同位素双稀释剂"的测定方法可实现严格的仪器质量分馏校正。文章以Mo同位素为例,详细介绍了同位素双稀释剂法的原理、计算方法以及应用多接收器等离子体质谱仪(MC-ICP-MS)进行Mo同位素组成高精度分析的方法。双稀释剂和标准样品的100Mo/97Mo使用Pd溶液的104Pd/102Pd标定,其他Mo同位素比值通过100Mo/97Mo标定。对100Mo/95Mo、98Mo/95Mo和97Mo/95Mo三组Mo同位素比值建立3个非线性方程,组成一个非线性方程组,在认为仪器质量分馏和自然分馏都符合指数法则的前提下,通过Taylor公式将非线性方程组转换成线性方程组,使用牛顿迭代法计算出样品的Mo同位素组成。在使用MC-ICP-MS分析过程中,每组数据采集20个数据点,最终的δ100Mo/95Mo、δ98Mo/95Mo和δ97Mo/95Mo是这20组数据得到的20组δ100Mo/95Mo、δ98Mo/95Mo和δ97Mo/95Mo的平均值。
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关键词:
- 双稀释剂 /
- 钼同位素 /
- 多接收器等离子体质谱仪 /
- Taylor公式 /
- 牛顿迭代法
Abstract: The key to increasing the accuracy of isotope measurement is the proper mass fractionation of instrumental mass discrimination calibrated by double spike. This paper took Mo isotopes as an example to introduce the principle, illustrate the calculation method of high-precision measurement isotope composition with double spike, and demonstrate the analytical method with multi-collector inductively coupled plasma-mass spectrometer(MC-ICP-MS). The 100Mo/97Mo of double spike and standard were calibrated by 104Pd/102Pd of Pd standard solution, and other ratios of double spike and standard were calibrated by 100Mo/97Mo. On the premise of that the instrument fractionation and the nature fractionation follow an exponential law, a system of nonlinear equations was converted to a system of linear equations using the Taylor formula, and the fractionation factor of the sample was calculated by the Newton iterative method. δ100Mo/95Mo, δ98Mo/95Mo and δ97Mo/95Mo were measured 20 times and averaged when analyzing with MC-ICP-MS.-
Key words:
- double /
- spike /
- Mo /
- isotope /
- multi-collector
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