电感耦合等离子体质谱法测量铼和锇同位素比值的质量分馏校正

The Correction of Mass Fractionation in the Measurement of Rhenium and Osmium Isotope Ratios by ICP-MS

用Re标准溶液测定出X Series-7电感耦合等离子体质谱(ICP-MS)检测器的死时间为43ns。由于Re和Ir的对数分馏系数线性相关,可以用Ir对Re进行在线分馏校正。利用配制的Re同位素比值标准溶液检验该方法,大多数校正值对标准值的相对偏差在±0.1%以下。ICP-MS测量时,Os的分馏系数与中位质量数成正比,采用由迭代方法得到的样品和稀释剂混合物的同位素比值(192Os/188Os)mix作为标准化值对其他Os同位素比值进行分馏校正。用已知Os同位素比值的标准溶液对该方法进行检验,结果表明,经校正后,大多数校正值与标准值的相对偏差在±0.3%以下。上述Re-Os同位素分馏校正方法将改善用ICP-MS进行Re-Os定年时的精密度和准确度。

The dead-time of the detector of inductively coupled plasma-mass spectrometry （ICP-MS） is 43 ns obtained by measuring Re standard solution. Since there is a liner correlation between isotopic fractionation factors of Re and Ir, Ir can be used to correct Re isotope fractionation. The test by measuring Re standard solution suggests that the relative deviations between corrected and standard values are, in most cases, less than ±0.1%. The isotopic fractionation factors of Os are proportional with the middle-mass of the isotopic pairs in the ICP-MS measurement. In this study, the Os isotope ratio of the mixture of the sample and spike Os （^192Os/^188OS）mix, obtained by iteration method is used as the normalization value to correct the isotope fractionation of other isotope ratios of Os. The test by measuring known Os isotopic solution suggests that the relative deviations between corrected and the reference values are less than ±0.3% in most cases. The correction method for Re-Os isotope fractionation presented by this paper will improve the precision and accuracy of the Re-Os dating by using ICP-MS.