改进的法拉第杯结构及其在富稀土元素磷灰石激光原位Sr同位素分析中的应用  

An Improved Faraday Cup Configuration and Its Applying in Sr Isotopic Analysis of Rich-REE Apatite by LA-MC-ICP-MS

作　　者：童喜润[1,2] 李小丹[1,2] 邱啸飞[1,2] 蔺洁[3] 卢山松[1,2] Tong Xirun;Li Xiaodan;Qiu Xiaofei;Lin Jie;Lu Shansong(Wuhan Center of China Geological Survey,Wuhan 430205,China;Research Center for Petrogenesis and Mineralization of Granitoid Rocks,Wuhan 430205,China;State Key Laboratory of Geological Processes and Mineral Resources,School of Earth Sciences,China University of Geosciences,Wuhan 430074,China)

机构地区：[1]中国地质调查局武汉地质调查中心,湖北武汉430205 [2]中国地质调查局花岗岩成岩成矿地质研究中心,湖北武汉430205 [3]中国地质大学地球科学学院,地质过程与矿产资源国家重点实验室,湖北武汉430074

出　　处：《地球科学》2024年第11期3904-3916,共13页Earth Science

基　　金：国家自然科学基金项目(No.42272229);中国地质调查局花岗岩成岩成矿地质研究中心开放基金项目(Nos.PMGR202017,PM202302);中国地质调查局武汉地质调查中心“潜龙计划”青年拔尖人才项目(No.QL2022-02).

摘　　要：稀土元素二价离子(REE^(2+))干扰校正是激光原位Sr同位素分析的难点.本研究将一种改进的MC-ICP-MS法拉第杯结构(能同步接收REE^(2+))与常规的干扰信号扣除法(RPSM)相结合,创新性实现了REE^(2+)干扰的准确校正.系统评估了改进的法拉第杯结构(IFCC)对REE^(2+)信号同步性以及比值(r:166,168,170Er^(2+)/167Er^(2+)和170,172,174,^(176)Yb^(2+)/173Yb^(2+))的影响.在IFCC上没有观察到REE^(2+)信号之间的脱耦现象,表明IFCC适合与RPSM结合用于REE^(2+)干扰校正;REE^(2+)信号比值(r)与Er和Yb的天然同位素丰度比值(R:^(166,168,170)Er/^(167)Er和^(170,172,174,176)Yb/^(173)Yb)近似相等(r/R≈1),指示在一定条件下可以使用R和测量的167Er^(2+)和173Yb^(2+)信号准确计算出^(166,168,170)Er^(2+)和^(170,172,174,176)Yb^(2+)信号强度,进而实现REE^(2+)干扰校正.加标溶液的Sr同位素SN-MC-ICP-MS分析结果表明,与IFCC结合,常规的干扰信号扣除法(RPSM,使用R做干扰校正系数)可有效校正Sr/Er≥3样品中的REE^(2+)干扰,而增强的干扰信号扣除法(EPSM,使用测量的REE^(2+)信号比值做干扰校正系数)可有效校正Sr/Er≥1样品中的REE^(2+)干扰.应用IFCC,使用LA-MC-ICP-MS对两个富稀土元素磷灰石标准物质Durango(Sr/Er=7.4)和UWA-1(Sr/Er=2.8)进行了Sr同位素组成分析,^(87)Sr/^(86)Sr的测定值分别为0.70627±0.00014(2SD,n=19)和0.70476±0.00019(2SD,n=20),与报道的TIMS或MC-ICP-MS测定值在误差范围内一致,证实了该方法的可靠性.It is still difficult to accurately correct the interferences of REE^(2+)in Sr isotopic analysis by LA-MC-ICP-MS.In this study,we corrected the interferences of REE^(2+)by RPSM(Routine Peak Stripping Method)combining use of an improved cup configuration of MC-ICP-MS allowing for synchronic detection of REE^(2+)signals.The effectiveness of IFCC(Improved Faraday Cup Configuration)was evaluated with respect to both the synchrony and the ratios of REE^(2+)signals.With IFCC,no decoupling of REE^(2+)signals was observed.This finding indicates that IFCC is well suited for RPSM to correct the interferences of REE^(2+).The ratios of REE^(2+)signals(r:^(166,168,170)Er^(2+)/^(167)Er^(2+)和^(170,172,174,176)Yb^(2+)/^(173)Yb^(2+))are approximately equal to(r/R≈1)the natural isotopic abundant ratios of Er an Yb(R:^(166,168,170Er/167)Er和^(170,172,174,176)Yb/^(173)Yb).This property cause IFCC to be well suited to correct interferences of REE^(2+)with the R and the measured signals of 167Er^(2+)and 173Yb^(2+).We also determined the Sr isotopic compositions of the Er and Yb-spiked 0.1μg/g NBS987 Sr solutions by SNMC-ICP-MS with IFCC,and the results attest that the interferences of REE^(2+)in the solutions with Sr/Er≥3 can be corrected using the RPSM(R as the interference correction factor),and those in the solutions with Sr/Er≥1 can be corrected using the EPSM(Enhanced Peak Stripping Method,measured r as the interference correction factor).Sr isotopic compositions of two rich-REE reference materials(Durango with Sr/Er=7.4,and UWA-1 with Sr/Er=2.8)were determined by LA-MC-ICP-MS with IFCC,and the determined 87Sr/86Sr of the two reference materials are 0.70627±0.00014(2SD,n=19)and 0.70476±0.00019(2SD,n=20),respectively,both of which agree with previously published values(determined by TIMS or MC-ICP-MS)within uncertainties.

关 键 词：SR 同位素 LA-MC-ICP-MS 稀土元素二价离子 磷灰石 地球化学. 

分 类 号：P597[天文地球—地球化学]