盐湖卤水中锶的二次离子交换分离及锶的同位素质谱法测定

SEPARATION OF STRONTIUM BY DUBLE ION-EXCHANGE AND THE DETERMINATION OF ISOTOPIC COMPOSITION OF STRONTIUM IN BRINE WATER SAMPLES BY MASS SPECTROMETRY

介绍了用国产树脂对盐湖卤水中锶的二次离子交换分离方法。从含有大量的Na,Mg及Ca的卤水体系中,用该方法分离出的锶能够满足同位素质谱分析,不产生同位素分馏效应。将本法用于盐湖卤水中锶同位素丰度比测定,其结果是满意的。

A double ion-exchange procedure is used to separate Sr in brine water in China. The sparat-ed Sr can be prepared for isotopic analysis with good results by mass spectrometry.Traditional, ion-exchange technique has been successfully used to separate Sr in geologic samples. The objective is to separate and purify enough Sr for several isotopic analysis. However using only single ion-exchange to prepare Sr for isotopic analysis in some sample with a great quantity of Na, Mg and Ca such as brine water is perhaps the most difficult task.A double ion-exchange procedure is described here. First, strong acid-resins (form H+, Shanghai No.1) were packed in quartz tube (0.8×25cm) for the first ion-exchange column, some in quartz tube (0.6×18cm), then changed into NH4+ form by passing 1mol/L NH4AC through the second ion-exchange column. Second, 1-5ml sample was allowed to pass through the first column, all of the Na, Mg and most of the Ca can be separated in 100ml with 1.8mol/L HC1 eluant at a flow rate of 0.8ml/min. Then 40ml 3mol/L HCl eluant containing some Ca and all Sr was collected, the eluant was dried to evaporate any trace of HC1. Third, 1ml 1: 1 HNO3 was added to dissolve the residue, then let it pass through the second column, the Ca can be separated completly in 130 ml with 0.75mpl/L NH4AC eluant, then use 4mol/L NF4AC 40ml to eluate all Sr, dry it again, and add 0.5ml 1:1 NHO3 to dissolve the sample. This step is to ensure routine mass spectrometry runs.In our experience, mass spectrometry runs can be made for samples with Ca/Sr ratios as high as 15:1 without adversely affecting instrumental performance. The single ion-exchange has worked successfully when the total size of Ca, Na, Mg is below 100mg and Sr content reaches 20μg in the samples. From the results we concluded that there is no isotopic fraction-ation after double ion-exchange procedure. Using this method a very good Sr isctopic results in brine water is obtained on VG-354 mass spectrometry.