氨水共沉淀法在锶同位素分析中的应用  

Application of Ammonia Solution Coprecipitation Method in Strontium Isotope Analysis

作　　者：刘文刚 魏双 张晓伟[2] 张健 周红英 LIU Wen-Gang;WEI Shuang;ZHANG Xiao-Wei;ZHANG Jian;ZHOU Hong-Ying(Tianjin Center,China Geological Survey(North China Center of Geoscience Innovation),Tianjin 300170,China;State Key Laboratory of Electroanalytical Chemistry,Changchun Institute of Applied Chemistry,Chinese Academy of Sciences,Changchun 130022,China)

机构地区：[1]中国地质调查局天津地质调查中心(华北地质科技创新中心),天津300170 [2]中国科学院长春应用化学研究所,电分析化学国家重点实验室,长春130022

出　　处：《分析化学》2025年第1期115-123,共9页Chinese Journal of Analytical Chemistry

基　　金：国家自然科学基金项目(Nos.42103033,22104137)资助。

摘　　要：在锶(Sr)同位素分析流程中,Sr的分离纯化对高精度Sr同位素比值的获取至关重要。本研究利用氨水作为沉淀剂,通过共沉淀法对地质样品中的Sr进行初步分离纯化,再结合阳离子交换树脂,可快速有效地获取高纯Sr组分。利用典型高Rb/Sr比值(质量比)标准物质JR-2,对氨水共沉淀实验条件进行优化。结果表明,使用3 mL 1 mol/L氨水作为沉淀剂,在120℃反应1 h,可有效去除90%以上的Rb、Na和K,Sr的回收率>95%。为了验证本分离流程的稳定性和适用范围,采用不同岩性和Rb/Sr比值的标准物质(JR-2、BCR-2、AGV-2、BHVO-2、GSP-2和W-2a)进行了实验验证,结果显示,通过氨水共沉淀反应,Rb、Na和K的去除率均>90%,Sr的回收率>95%。为了进一步验证本方法对高Rb/Sr比值样品的适用性,在流纹岩标准物质JR-2中添加Rb,调整其Rb/Sr比值至500。结果表明,本分离流程仍能有效实现Rb和Sr的分离,结合热电离质谱仪(TIMS)成功获得了高精度Sr同位素分析结果。氨水作为沉淀剂具有成本低廉、流程空白低、流程简单和适用范围广等优点,氨水共沉淀法和阳离子交换树脂相结合可以快速实现地质样品中Sr的纯化,尤其为高Rb/Sr比值样品的高精度Sr同位素分析提供了一种新的分离思路,具有广阔的应用前景。In the process of strontium(Sr)isotope analysis,the separation and purification of Sr are crucial for obtaining high-precision Sr isotope ratios.In this work,ammonia solution was used as a precipitating agent to initially separate and purify Sr from geological samples through coprecipitation,followed by the combination with cation-exchange resin to quickly and effectively obtain high-purity Sr components.The experimental conditions of ammonia coprecipitation reaction were optimized using typical high Rb/Sr ratio(mass ratio)standard sample JR-2.The results showed that using 3 mL of ammonia(1 mol/L)as the precipitating agent,at 120℃for 1 h,could effectively remove more than 90%of Rb,Na and K,with Sr recovery exceeding 95%.To verify the stability and applicability of this separation process,geological standard samples(JR-2,BCR-2,AGV-2,BHVO-2,GSP-2,W-2a)with different rock types and Rb/Sr ratios were practically validated.The results demonstrated that the coprecipitation process with ammonia solution removed more than 90%of Rb,Na and K,with Sr recovery greater than 95%.To further assess the applicability of this method for samples with high Rb/Sr ratios,Rb was added to the rhyolite standard material JR-2,adjusting its Rb/Sr ratio to 500.The results showed that this separation process could still effectively achieve the separation of Rb and Sr,and high-precision Sr isotope analysis results were successfully obtained by combining thermal ionization mass spectrometer(TIMS).Ammonia solution,as a precipitating agent,offered advantages such as low cost,low procedural blanks,simplicity,and a wide range of applicability.Therefore,the combination of ammonia solution coprecipitation and cation-exchange resin enabled rapid Sr purification from geological samples,providing a novel separation approach for high-precision Sr isotope analysis of samples with high Rb/Sr ratios,with broad application prospects.

关 键 词：氨水沉淀剂 阳离子交换树脂 地质样品 锶同位素分析 

分 类 号：O657.63[理学—分析化学] TQ132.33[理学—化学]