利用DCTA和HIBA快速有效分离Rb-Sr、Sm-Nd的方法

介绍了一种新的Rb_Sr、Sm_Nd化学分离方法,以用于地质样品的同位素测试.方法选用AG50W×8阳离子交换树脂,并先后采用不同的淋洗剂进行分离提纯.首先用常规方法使用盐酸作为淋洗剂将Rb_Sr和REE分开并与其它大部分元素分离,然后使用DCTA和嘧啶的混合溶液(D.P.E.)作为淋洗剂分离Rb和Sr,使用HIBA作为淋洗剂在很小体积(0.6mL)的阳离子交换树脂中分离Sm和Nd.使用这样的分离方法可以有效的将一些干扰离子(如Mg、Ca、Ba)和Sr分离,同时使用该分离方法可以提高分离效率,缩短分离时间,减少试剂用量,降低实验过程空白.用该方法分离国际玄武岩标样BCR_2后的Sr同位素测试结果(87Sr/86Sr=0.705018±3)和Nd同位素测试结果(143Nd/144Nd=0.512616±9)与已经报道的测试结果基本一致,说明本次研究采用的新分离方法效果良好.

Separation Method of Rb-Sr, Sm-Nd Using DCTA and HIBA

Generally, Rb-Sr and Sm-Nd were separated from geological samples using H~ form cation-exchange chromatography after dissolution with a mixed acid consisting of HF, HClO-4, and HNO-3. In this case, large amounts of ion-exchange resin in a long column (e.g., 20 cm), necessitating large elution volume and long separation time are required. In this study, we have established a new method simultaneously separating Rb-Sr, Sm-Nd for isotopic analysis of geological samples by adopting resin of AG50W8 and different eluent reagents. Firstly, rare earth elements are separated from Rb-Sr in geological samples by using normal method of cation-exchange chromatography with eluent of HCl. Then Rb and Sr are separated and purified by using a mixed eluent of pyridinium and DCTA complex through small amounts of cation-exchange resin (l.0 mL). At the same time, Sm and Nd are separated and purified by using HIBA as an eluent through extremely small volumes of cation-exchange resin (0.6 mL). This method improved the separation efficiency and separated Sr from coexisting large amounts of Mg, Ca and Ba especially in carbonate samples much better than normal eluent of HCl. This method also greatly reduced the total elution volumes and thus lowered the procedural blankS. The method has made it possible to precisely determine the isotopic composition of Sr and Nd in low concentration samples, such as uttramafic rocks and sulfide samples. By using this separation method, analyses for the international basalt standard of BCR-2 yielded mean ()~(87)Sr/()~(86)Sr of 0.705 0183 and ()~(143)Nd/()~(144)Nd of 0.512 6169 which are consistent with those obtained by other separation methods.