乙醚萃取分离-电感耦合等离子体质谱法测定岩石样品中铊

Determination of thallium in rock sample by inductively coupled plasma mass spectrometry with ether extraction separation

准确测定岩石样品中铊的含量,对于有效监控矿物开采和加工过程中的铊污染,具有重要意义。因岩石样品中铊含量很低,故一般在测定前需对铊进行分离富集以消除大量基体元素对铊测定的干扰。实验采用盐酸-硝酸-氢氟酸-高氯酸分解岩石样品,在样品溶液中加入氢溴酸使之与三价铊(Tl^3+)发生络合反应生成溴化铊,用乙醚萃取溴化铊,实现了铊与基体元素的分离。将乙醚萃取液于60 ℃电热板加热挥发以除去乙醚,再用加入硝酸加热消解的方式除去残余乙醚,加硝酸和沸水浸取,以5.0 ng/mL 185Re为内标,205Tl^+为测定对象,采用电感耦合等离子体质谱法(ICP-MS)进行测定,实现了对岩石样品中铊的测定。实验表明,铊质量浓度在5.00~40.00 ng/mL范围内与铊信号强度和内标元素信号强度的比值呈线性关系,相关系数为0.999 8,方法检出限为0.004 9 ng/mL。将实验方法应用于岩石实际样品,测定结果的相对标准偏差(RSD,n =6)均小于5%,加标回收率为96%~103%。采用实验方法测定岩石标准物质中铊,测定值与认定值基本一致。

The accurate determination of thallium content in rock samples was of great significance for the monitoring of thallium pollution in mineral mining and processing. Since the content of thallium in rock sample was usually very low, the separation and enrichment of thallium should be conducted before determination of thallium to eliminate the interference of many matrix elements. The rock sample was decomposed with hydrochloric acid-nitric acid-hydrofluoric acid-perchloric acid. The hydrobromic acid was added into sample solution to react with Tl^3+ to form thallium bromide complex. The thallium bromide complex was then extracted with ether, realizing the separation of thallium from matrix elements. The ether extract liquor was heated on electric hot plate at 60 ℃ to remove ether by volatilization. The residual ether was further removed by digestion with heating and addition of nitric acid. After leaching with nitric acid and hot water, the content of thallium was determined by inductively coupled plasma mass spectrometry (ICP-MS) with 5.0 ng/mL 185 Re as internal standard and 205 Tl^+ as determination object. Thus, the determination method of thallium in rock sample was realized. The experimental results showed that the mass concentration of thallium in the range of 5.00-40.00 ng/mL was linear to the ratio of signal intensity to thallium and internal standard. The correlation coefficient was 0.999 8. The detection limit of method was 0.004 9 ng/mL. The proposed method was applied for the analysis of rock actual samples. The relative standard deviations (RSD, n =6) of determination results were all less than 5%. The spiked recoveries were between 96% and 103%. The content of thallium in certified reference material of rock was determined, and the found results were basically consistent with the certified values.