电感耦合等离子体质谱法测定高纯碳化钨粉中18种痕量杂质元素

高纯碳化钨粉作为超细硬质合金生产的原料,其杂质元素含量的分析和控制十分重要。采用电感耦合等离子体质谱法(ICP-MS)测定高纯碳化钨粉时,需先将样品中碳完全氧化除去后再进样测定,否则不溶的游离碳会堵塞仪器进样系统,引起信号波动,严重干扰测定。实验采取将样品于600~800℃马弗炉中氧化的方式除去游离碳,然后再用氨水消解样品,在优化测定同位素和仪器工作参数的基础上,采用屏蔽炬冷焰技术测定钙、铁、铬、镁、铝、锰、钴、镍、铜,采用常规模式测定砷、铋、镉、钼、铅、锑、锡、钛、钒以消除质谱干扰,以钨基体匹配法绘制校准曲线克服基体效应,控制基体质量浓度为0.5mg/mL,实现了ICP-MS对高纯碳化钨粉中这18种元素的测定。在选定的工作条件下,各元素校准曲线的线性相关系数均大于0.9995,方法检出限在0.006~0.330μg/g之间。应用实验方法测定高纯碳化钨粉样品中18种杂质元素,锡测定值的相对标准偏差(RSD,n=11)为24%,除锡外其他元素的RSD(n=11)均小于10%,测定值与直流电弧原子发射光谱法(ARC-AES)结果基本吻合。因高纯碳化钨粉样品在马弗炉中氧化后主要成分为三氧化钨,因此采用实验方法对三氧化钨标准样品中18种杂质元素进行测定以验证方法正确度,结果表明,测定值与认定值基本一致。

Determination of eighteen trace impurities in high purity tungstencarbide powder by inductively coupled plasma mass spectrometry

High purity tungsten carbide powder was the raw material for the production of ultrafine cemented carbide. It was of great importance for analysis and control of its impurity elements contents. During the determination of impurity elements in high pure tungsten carbide powder by inductively coupled plasma mass spectrometry (ICP-MS), the carbon in sample should be completely oxidized and removed before determination. Or else the insoluble free carbon would cause the blocking of sampling system, leading to the fluctuation of signal intensity and serious interference of determination. The tungsten carbide powder sample was oxidized in muffle furnace at 600-800℃ to remove free carbon. Then the sample was digested with ammonium hydroxide. After the test isotopes and working parameters of instrument were optimized, the contents of calcium, iron, chromium, magnesium, aluminum, manganese, cobalt, nickel and copper were determined by shield torch cool plasma technology, and the contents of arsenic, bismuth, cadmium, molybdenum, lead, antimony, tin, titanium and vanadium were determined at normal mode to eliminate the mass spectral interference. The calibration curve was plotted by matrix matching method of tungsten to overcome the matrix effect. The matrix mass concentration was controlled at 0.5mg/mL. Consequently, a determination method of these eighteen elements in high-purity tungsten carbide powder by ICP-MS was realized. Under the selected working conditions, the linear correlation coefficients of calibration curves for all elements were higher than 0.9995. The detection limits of method were in range of 0.006-0.330μg/g. The experimental method was applied to the determination of eighteen impurities in high-purity tungsten carbide powder samples. The relative standard deviations (RSDs, n=11) were less than 10% except for tin (24%). The results were basically consistent with those obtained by direct-current arc atomic emission spectrometry (ARC-AES). Since the main composition of high-purity tungsten carbide powder sample after oxidization in muffle furnace was tungsten trioxide, eighteen impurities in certified reference material of tungsten trioxide were determined according to the experimental method to verify the trueness of method. The results showed that the determination results were consistent with the certified values.