用于多接收器等离子质谱Mg同位素测定的分离方法研究  

Separation of Mg for isotope determination by MC-ICP-MS

作　　者：李世珍[1] 朱祥坤[1] 何学贤[1] 杨淳[1] 赵新苗[2] 唐索寒[1] 

机构地区：[1]中国地质科学院地质所国土资源部同位素重点实验室,北京100037 [2]中国科学院地质与地球物理研究所,北京100029

出　　处：《岩石矿物学杂志》2008年第5期449-456,共8页Acta Petrologica et Mineralogica

基　　金：国家自然科学基金重点资助项目(40331005);国家自然科学基金资助项目(40473039;40673047)

摘　　要：利用多接收器等离子体质谱仪(MC-ICP-MS)进行同位素组成的准确测定,必须首先对待测样品中元素进行分离纯化。目前,用于分离Mg的主要方法为阳离子树脂交换方法。然而,利用阳离子树脂不能有效除去Mg接收液中的Fe、Al,而溶液中Fe、Al会明显干扰样品中Mg同位素组成的测定。本研究结合离子交换法和共沉淀法,探讨了针对不同种类样品的Mg分离纯化方法,分离提取了实际样品中Mg并进行了同位素组成的测定。实验结果显示:①对于m(Fe)/m(Mg)≤0.1、m(Al)/m(Mg)≤0.2、m(Na)/m(Mg)≤1的样品,经过AG50 W-X12树脂一次交换分离,即可用于Mg同位素组成的测定;②对于m(Fe)/m(Mg)≤0.1、m(Al)/m(Mg)≤0.2、m(Na)/m(Mg)>1的样品,利用AG50 W-X12树脂二次交换分离,可以满足MC-ICP-MS对Mg同位素测定的要求;③对于含有m(Fe)/m(Mg)>0.1、m(Al)/m(Mg)>0.2、m(Na)/m(Mg)≤1的样品,可先利用稀释50倍的稀氨水沉淀除去样品中的Fe、Al后,再经过AG50 W-X12树脂一次交换分离,可以满足MC-ICP-MS对Mg同位素测定的要求;④对于含有m(Fe)/m(Mg)>0.1、m(Al)/m(Mg)>0.2、m(Na)/m(Mg)>1的样品,可先利用稀释50倍的稀氨水滴定沉淀除去样品中的Fe、Al后,再经过AG50 W-X12树脂二次交换分离,可以满足MC-ICP-MS对Mg同位素测定的要求;⑤运用所建立方法对海水和地幔样品进行了Mg的分离和同位素组成的测定,其中,青岛附近海水的同位素组成为:δ25MgDSM3=-0.43‰,δ26MgDSM3=-0.84‰;葫芦岛附近海水的同位素组成为:δ25MgDSM3=-0.44‰,δ26MgDSM3=-0.85‰。Accurate determination of Mg isotopes using MC-ICP-MS requires anadequate separation of dements from bulk samples. Cation exchange chromatography has been used to separate Mg from the matrix elements. However, the removal of Fe and Al from Mg solution is not effective, and Fe and Al do affect the accurate determination of Mg isotope by MC-ICP-MS. Methods for different kinds of samples were investigated based on exchange chromatography using AG50W-X12 and coprecipitation of Fe and Al using diluted NH3·H2O, and Mg isotope composition of natural sample was determined after purification. The results show that ①It is enough to separate Mg from the bulk samples using the resin column one time when rn （Fe）/m （Mg）≤0.1,m（A1）/m（Mg）≤0.2 and m（Na）/m（Mg）≤l in solution;②It is enough to separate Mg from the bulk samples using the resin column two times when rn （Fe）/m （Mg） 40.1, m （A1）/m （Mg）≤0.2 and m （Na）/m （Mg）〉1 in solution; ③It is essential to obtain Mg solution using coprecipitation of Fe and Al by NH3·H2O and separation of Mg by cation exchange chromatography one time when m （Fe）/m （Mg） 〉0.1, m（Al）/m（Mg）〉0.2 and m（Na）/m（Mg）≤l in solution;④ It is essential to obtain Mg solution using coprecipitation of Feand Al by NH3· H2O and separation of Mg by cation exchange chromatography two times when m （Fe）/m （Mg） 〉 0.1, m（Al）/m（Mg）〉0.2 and m（Na）/m（Mg）〉1 in solution; ⑤ The Mg isotopic compositions of the sea water around Qingdao City are δ^25MgDSM3 = -0.43‰ and δ26MgDSM3 =-0.84‰; The Mg isotopic compositions of the sea water around HLD are δ^25MgDSM3 =-0.44‰ and δ26MgDSM3 =-0.85‰.

关 键 词：MC-ICP-MS Mg同位素组成 分离纯化 共沉淀方法 

分 类 号：P597.2[天文地球—地球化学]