高氯酸-氟化氢铵-硝酸密闭消解电感耦合等离子体质谱法测定页岩中稀土元素

通过对页岩中稀土元素(REE)含量特征及稀土分布模式的探讨,可以了解页岩矿区的沉积环境特征及物质来源信息,因此有必要建立稀土元素准确定量分析方法。页岩样品组成复杂、有机质含量高,样品的完全消解是准确测定其稀土含量的基础。在采用X射线衍射法对样品进行组成分析的基础上,利用氟化氢铵在加热过程中可分解产生氢氟酸的特性,采用高氯酸、氟化氢铵、硝酸密闭消解样品,以电感耦合等离子体质谱法(ICP-MS)进行测定,实现了对页岩中稀土元素的测定。在上述优化的实验条件下对稀土混合标准溶液系列进行测定,结果表明,各稀土元素质量浓度在1~100ng/mL范围内线性良好,线性相关系数均大于0.9996,方法检出限为0.002~0.473μg/g。将实验方法应用于页岩标准物质中稀土元素的测定,测定值与认定值吻合,相对误差的绝对值不大于6.77%。采用实验方法对页岩实际样品进行测定,测得结果的相对标准偏差(RSD,n=6)均低于10%。将实验方法与密闭高温高压溶样ICP-MS进行对照分析,二者结果基本一致。

Determination of rare earth elements in shale by inductively coupledplasma mass spectrometry with perchloric acid-ammoniumbifluoride-nitric acid closed digestion

The discussion of content characteristic and distribution pattern of rare earth elements (REEs) in shale was helpful to understand the information of shale area such as the sedimentary environment characteristic and matter source. Therefore, it was necessary to establish the accurate and quantitative analysis method of REEs. The shale samples usually had complicated composition and high-content organic matters, so the complete digestion of sample was the foundation to accurately determine the content of REEs. The composition of sample was analyzed by X-ray diffraction. Based on the property that hydrofluoric acid could be produced during heating of ammonium bifluoride, the sample was digested in closed system by perchloric acid, ammonium bifluoride and nitric acid. Then the sample solution was determined by inductively coupled plasma mass spectrometry (ICP-MS). Consequently, the determination of REEs in shale were realized. The mixed standard solution series of REEs were determined under the optimized experimental conditions. The results showed that the linearity was good for each REEs with mass concentration in range of 1-100ng/mL. The linear correlation coefficients were all higher than 0.9996. The detection limits were between 0.002μg/g and 0.473μg/g. The proposed method was applied for the determination of REEs in certified reference material of shale. The results were consistent with the certified values, and the absolute values of relative errors were not than 6.77%. The shale actual sample was determined according to the experimental method, and the relative standard deviations (RSD, n=6) of determination results were all less than 10%. The experimental method was compared with ICP-MS after sample dissolution in closed high-temperature and high-pressure system. The determination results were consistent.