等离子体质谱法在地质样品铅同位素比测定上的应用

Studies in the Application of ICP-MS to the Determination of Lead Isotope Ratios in Geological Materials

本文研究了等离子体质谱法在地质样品铅同位素比测定上的应用。对仪器的质量歧视效应进行了观察和讨论,并对比了它的两种校正方法。溶样方法对某些样品的同位素比测定结果影响较大,应根据地质研究的要求选择溶样方法。铅同位素比的测量精度(RSD)一般为0.1-1%;与TIMS值的相对偏差为0.1-2%。分析一个样品的时间平均约8分钟。

Lead isotope ratios have been determined in large numbers of geological samples on an ICP mass spectrometer. An unstable instrumental mass discrimination Was observed and corrected by using NBS SRM 98 1 as an external stan- dard. An alternative method of correction using thallium as an internal standard has been tried and the preliminary data obtained are presented for comparison. Sample dissolution is important in determining the lead isotope ratios for some rock samples. Different procedures should therefore be used for different geological studies. Lead isotope ratios can be measured by ICP-MS at the rate of 5 sample solutions per 40-minutes with p ecisions of 0.1-1% RSD and relative deviations of 0.1-2% with respect to TIMS values.