电感耦合等离子体质谱(ICP-MS)法测定高钨基体样品中稀土元素的含量

Determination of Rare Earth Elements in High Tungsten-bearingSamples by Inductively Coupled Plasma Mass Spectrometry(ICP-MS)

准确测定钨矿和钨酸盐晶体等高钨基体样品中稀土元素的含量有助于开展矿床地球化学特征研究及钨酸盐激光晶体材料的制备和性质研究。在采用电感耦合等离子体质谱(ICP-MS)法测定高钨基体样品时,为了考察高钨及高含量阳离子等基体组成对分析结果的影响,针对Na_(2)WO_(4)、CaWO_(4)、NaY(WO_(4))_(2)、MnWO_(4)和(Fe,Mn)WO_(4)等高钨基体样品,采用硝酸和氢氟酸高压密闭消解,加入稀土元素并用2%HNO_(3)溶液稀释定容配制成稀土元素浓度为1 ng/g的基体匹配标准溶液;同时,直接用2%HNO_(3)溶液配制稀土元素浓度相同的非基体匹配标准溶液以对比两种基体溶液中稀土元素的相对灵敏度系数(RSCs)差异。结果显示,基体匹配溶液与2%HNO_(3)溶液中稀土元素的RSCs相对偏差小于15%,表明基体效应的影响可以忽略不计。进而,为了准确测定常见高钨基体样品中稀土元素的含量,建立了基于ICP-MS的高钨基体样品中稀土元素准确定量分析方法,方法线性关系好(R^(2)>0.9997),检出限低(0.5~27.9 pg/g),准确度理想(相对误差-6.2%~10.7%)。用来测定钨酸钙单晶实际样品中稀土元素的含量,并将其与基体匹配法的测定结果进行比对,结果显示,两者大部分元素相对偏差为0.80%~12.8%,说明所建立的分析方法可靠,能用于定量测定高钨基体样品中稀土元素的含量。

Accurate determination of rare earth elements(REEs)in high tungsten-bearing samples is significant for geochemistry research and synthesis of high-performance tungstate laser crystals.In order to investigate the influence of matrix compositions including high tungsten and high content of cations,on the results obtained by the inductively coupled plasma-mass spectrometry(ICP-MS),several high tungsten-bearing samples such as Na_(2) WO_(4),CaWO_(4),NaY(WO_(4))2,MnWO_(4) and(Fe,Mn)WO_(4) were digested by HNO_(3) and HF,were doped with REEs and diluted by 2%HNO_(3) solution.It was treated as the matrix-matched solutions,and the relative sensitivity coefficients(RSCs)of REEs in which were compared with those in the non-matrix-matched solutions(i.e.,2%HNO_(3) only doped with REEs).No obvious difference of RSCs was found among these solutions with relative deviation less than 15%,which indicated that the influence of matrix effects induced by high tungsten and high content of cations in high tungsten-bearing samples was negligible.Then,a methodology for accurate determination of REE contents by ICP-MS was developed with good liner relationship(R^(2)>0.9997),low detection limit(0.5-27.9 pg/g)and desirable accuracy(relative error:-6.2%-10.7%).It was further used to determine the REE contents in the real CaWO_(4) single crystals.The results were close to those determined by matrix-matched ICP-MS with relative deviation of 0.80%-12.8%.It demonstrates that the proposed method can be used to accurately determine REE contents in the high tungsten-bearing samples.