脉冲增压毛细管分离富集ID-ICP-MS测定地质样品中微量锂的方法研究

采用一种脉冲增压毛细管柱 ,用于锂的分离富集。其原理类似于高效液相色谱 ,但使用钢瓶气为动力脉冲驱动液相在固定相中流动。使用粒度很细的固定相材料 ,惰性气体和液相脉冲交替通过固定相 ,使固定相的死体积减小到最低程度 ,从而获得很高的分离富集系数。试验了一种无机固定相材料和树脂材料用于锂的分离富集。结果表明 :无机材料能高效富集锂 ,但选择性较差、本底杂质较多 ;阳离子交换树脂分离效果好、本底低 ,能从镁、钙等大多数离子中很好地将锂分离 ,几乎没有拖尾现象 ,回收率达到 97% ,分离纯度高。分离后 ,用 ICP-MS测定锂同位素的比值 ,具有较高的测量精密度。用同位素稀释电感耦合等离子体质谱( ID-ICP-MS)测定地质样品中微量锂 ,结果相对标准偏差 sr<3%。方法检出限低 ,精密度高 ,分析速度快 ,是测定锂的较理想方法。

Pulse-pressurized Capillary Column for Separation and Preconcentration of Lithium and Determination of Trace Lithium in Geological Samples by ID-ICP-MS

A method called pulse-pressurized capillary column is used for preconcentration and separation of Li, followed by determination of trace Li in geological samples by ID-ICP-MS. The key points of the method are: stationary phase with micro size 200～400 mesh resin, capillary column with inside length of 50 mm and diameter of 1.5 mm, and mobile phase pulse-powered by pressurized argon gas. The dull volume of the column bed can be reduced to minimum and high preconcentration efficiency is able to be obtained. Elution volume is only 1.0 mL, but recovery over 97%. Both inorganic material and cation exchange resin are tested as stationary phase in this work. The results show that cation exchange resin is better than inorganic material for Li separation, even though both materials are of high preconcentration ability. The method is used to preconcentrate Li and separate matrix in geological samples, and contents of Li in those samples determined by ID-ICP-MS, giving precise of 3% and good accurate results.