岩石样品中硼同位素组成测定

Determination of Boron Isotopic Composition of Rock Samples

基于热电离质谱测试技术,开展岩石样品中硼的分离纯化及其同位素组成测试研究。建立了一种用氢氟酸溶解岩石样品、阴离子交换树脂对硼进行分离和纯化、热电离质谱法测试硼同位素的方法。讨论了温度和时间对样品消解的影响,考察了分离效果和硼的回收率,采用硼同位素标准物质、岩石成分分析标准物质和天然岩石样品进行了方法准确度验证。结果表明:岩石样品最佳消解条件是在60℃下超声6 h后再加热3 h。即使在甘露醇的保护下,也需控制消解温度,当遇到难溶样品时可以适当增加样品的消解时间。阴离子交换树脂法可有效对硼进行分离纯化,所有干扰元素均能与硼分离彻底,全流程回收率在95%以上,分离过程中硼的分馏效应可以忽略。对GSR-1花岗岩标准样品硼同位素测试得到的δ11B值为-13.1±0.4‰(n=10)与文献值在误差范围内是一致的,不同种类岩石样品重复分析结果标准偏差优于0.6‰。说明建立的岩石样品硼同位素测试方法过程简单,易于操作,能够满足地质研究的需要。

Based on the technique of thermoionization mass spectrometry,the separation of boron from rock samples and its isotopic composition have been studied in this paper.A method was developed for the separation and purification of boron by anion exchange resin and the determination of boron isotope by thermoelectric ionization mass spectrometry.The effects of digestion temperature and time of sample digestion were discussed,the separation effect and the recovery of boron were investigated,and the accuracy of the method was verified by using boron isotope reference material,GSR⁃1 rock composition analysis reference material and natural rock samples.The results showed that the optimal digestion condition of rock samples was ultrasonic at 60℃for 6 h and then heating for 3 h.Even under the protection of mannitol,it is necessary to control the digestion temperature,and the digestion time of the sample can be appropriately increased when the sample is insoluble.The anion exchange resin method can effectively separate and purify boron,all interfering elements can be completely separated from boron,the recovery rate of the whole process is more than 95%,and the fractionation effect of boron can be ignored in the separation process.Theδ11B value obtained by boron isotope test of GSR⁃1 granite standard sample is⁃13.1±0.4‰(n=10),which is consistent with the literature value within the error range,and the standard deviation of repeated analysis results of different kinds of rock samples is better than 0.6‰.This method is simple,easy to operate and can meet the needs of geological research.