The presence of 87Rb causes isobaric interference of 87Sr for Multiple Collector-Inductively Coupled Plasma-Mass Spectrometric ( MC-ICPMS) measurements. 87Sr/86 Sr isotopic composition of rocks with Rb/Sr ≤0.0005 after chromatography separation can be effectively corrected by using a traditional Rb-interference calibration. However, the traditional calibration method is not valid for solutions with high Rb/Sr ratio which cannot completely remove isobaric interference of 87Rb to obtain an accurate 87Sr/86Sr ratio. The two curves of the 87Sr/86Sr isotope ratio and Rb/Sr element content ratio were obtained by two sets of experiments to calibrate Rb interference in this work. Based on theoretical analysis, a new calibration method is reported, including an isotope fractionation calibration. The method yields an accurate 87Sr/86Sr ratio for geology samples with Rb/Sr <0. 2 after chemical separation, and reduces requirements of chemical separation for isotope measurements by MC-ICPMS. However, the measurement accuracy for geological samples with Rb/Sr > 0. 2 after chemical separation wassignificantly lower due to mass fractionation and memory effect, which can not be calibrated to obtain an accurate Sr isotopic composition by any kind of calibration method.%在利用多接收电感耦合等离子体质谱( MC - ICPMS)进行Sr同位素研究中,87Rb对于87Sr干扰严重.岩石样品经化学分离后,若Rb/Sr≤0.0005,可以采用传统的Rb干扰扣除方法对87Sr/86 Sr测定值进行准确校正;但如果样品经化学分离后仍含有较高的Rb/Sr比,同量异位素的干扰不能完全消除,则无法准确校正87 Sr/86 Sr测定值,直接影响测试结果的准确度.本文针对Rb含量较高的地质样品设计两组实验,确定了87Sr/86Sr同位素比值与Rb/Sr元素含量比值的关系曲线,并在理论分析的基础上,提出包含同位素分馏校正在内的重叠干扰校正方法.通过实际地质样品验证,该校正方法在较高含量Rb元素共存(Rb/Sr＜ 0.2)的Sr纯化液中,能够较为准确地测量87Sr/86Sr同位素比值,降低了MC - ICPMS分析地质样品中Sr同位素时对化学分离步骤的要求.而对于Rb/Sr＞0.2的地质样品,因仪器分馏效应和记忆效应影响,测试精确度大大降低,无论采用何种校正方法均无法得到准确的Sr同位素组成.
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