碳酸盐岩样品中镍和钪的电感耦合等离子体质谱分析与干扰校正方法

Inductively Coupled Plasma-Mass Spectrometric Analysis of Nickel and Scandium in Carbonate Rock Samples and Interference Correction Methods

电感耦合等离子体质谱法(ICP-MS)已在碳酸盐岩微量元素测试中得到了广泛应用。然而,采用ICP-MS分析碳酸盐岩中含量较低的Ni(1.6~50.5μg/g)和Sc(0.3~6μg/g)时,信号值会受到高含量CaO(可高达56%)和MgO(可高达21%)的显著干扰,使测试值远高于真实值,从而无法获得准确的待测元素含量。为解决这一问题,本文通过实验探寻测试中的主要干扰因素,再据此确定相应的校正方法。首先,利用Ca和Mg的单标系列对碳酸盐岩ICP-MS测试中的高含量Ca、Mg对Ni、Sc的干扰分别进行研究,发现高含量Mg对Ni和Sc的测试存在基体效应的非质谱干扰;而高含量Ca则形成氧化物、氢氧化物及多原子离子对Ni和Sc形成质谱干扰,并且这一干扰程度与溶液中Ca含量呈良好的线性关系。然后,进一步选择碳酸盐岩国家一级标准物质作为校正载体以消除Mg的基体效应,同时根据样品溶液中CaO含量与Ni、Sc受干扰程度呈现的良好线性关系,提出了扣除拟合干扰的校正方法。相对于前人仅利用单标对实际样品进行干扰校正而言,本方法采用国家一级标准物质作为校正载体,克服了基体效应的干扰。并经GBW07108等五个碳酸盐岩国家一级标准物质验证,测定值与认定值相符,相对标准偏差(RSD,n=10)小于5.5%。将未知碳酸盐岩样品的校正结果与电感耦合等离子体发射光谱法(ICP-OES)及X射线荧光光谱法(XRF)测试结果进行对比,相对偏差均小于15%。该校正方法简单易行,测定结果准确可靠。

BACKGROUND:Inductively coupled plasma-mass spectrometry(ICP-MS)has been widely used in the determination of trace elements in carbonate rocks.Due to the low Ni(1.6-50.5μg/g)and Sc(0.3-6μg/g)in carbonate rocks,the signal values are obviously interfered by high CaO(up to 56%)and MgO(up to 21%)during ICP-MS determination,resulting in the test value much higher than the true value.OBJECTIVES:To solve the problem of non-mass spectrum interference and mass spectrum interference of Ni and Sc during ICP-MS analysis of carbonate rocks and use appropriate correction method.METHODS:The single standard series of Ca and Mg and national first-level reference materials of carbonate rocks were used to study the interference of high content of Ca and Mg on Ni and Sc in the carbonate during ICP-MS analysis.Testing of the single standard series was aim to explore ways of interference on Ni and Sc by high content of Ca and Mg in solution.The national first-level reference material of carbonate rock was further selected as the calibration carrier to eliminate the matrix effect of Mg.At the same time,according to the good linear relationship between the content of CaO in the sample solution and the interference degree of Ni and Sc,the interference equations of CaO and△Ni and△Sc were fitted respectively,and used for interference deduction of Ni and Sc in several national first-level reference materials and unknown samples of carbonate rocks.The accurate test values of Ni and Sc in carbonate rocks by ICP-MS were obtained.RESULTS:It was found that the high content of Mg had a non-mass spectrometric interference matrix effect on the analysis of Ni and Sc.High content of Ca forms oxides,hydroxides and polyatomic ions,resulting in mass spectrometric interference on Ni and Sc.The degree of interference had a good linear relationship with the Ca content in the solution.Compared with a single standard to perform interference correction on actual samples,this method used national first-level standard materials as the calibration carrier,which overcomed the interference of matrix effects.Verified by GBW07108 and other five national primary standard materials of carbonate rocks,test values agreed with the standard values,with a relative standard deviation(RSD,n=10)of less than 5.5%.Correction results of the unknown carbonate samples were compared with the results of the inductively coupled plasma-optical emission spectroscopy(ICP-OES)and the X-ray fluorescence spectrometer(XRF),respectively,the relative deviation was less than 15%.CONCLUSIONS:The correction method proposed in this paper has solved the mass spectral interference and non-mass spectral interference in ICP-MS analysis of Ni and Sc in carbonate rocks.The method is simple and feasible,and the results are accurate and reliable.