电感耦合等离子体串联质谱法测定高纯钼中痕量镉

Determination of trace cadmium in high-purity molybdenum by inductively coupled plasma tandem mass spectrometry

高纯钼中痕量镉因受到钼氧、钼氮等多原子离子的严重干扰,即使采用高分辨质谱仪也无法准确分析。为了有效消除干扰,采用串联质谱的反应池技术,选取111Cd为分析同位素,分别在H2和NH3模式下讨论了1000μg/mL Mo标准溶液和1000μg/mL Mo-1.000ng/mL Cd混合标准溶液的信号强度以及背景等效浓度(BEC)的变化趋势,并优化了气体流速;最终选择0.4mL/min的NH3做反应气,此时1 000μg/mL Mo标准溶液中Cd的背景等效浓度约为0.8ng/L,表明钼氧、钼氮等多原子离子对Cd的干扰可被有效地消除。在选定的仪器测试条件下,校准曲线的线性相关系数大于0.999 9,方法检出限为2.7ng/g,加标回收率为93%~105%。采用所建立的电感耦合等离子体串联质谱(ICP-MS/MS)测定高纯钼中痕量镉的方法分析高纯钼样品,测得结果的相对标准偏差(RSD,n=5)为0.50%~4.2%。

The determination of trace cadmium in high-purity molybdenum is severely affected by multi-atomic ions such as molybdenum-oxygen and molybdenum-nitrogen,so it difficult to accurately analyze it even using high-resolution mass spectrometer.In order to effectively eliminate the interference,the reaction cell technique of tandem mass spectrometry was employed.111 Cd was selected as the analytical isotope.The variation trends of signal strength of 1 000μg/mL Mo standard solution and 1 000μg/mL Mo-1.000 ng/mL Cd mixed standard solution as well as background equivalent concentration（BEC）were discussed under H2 mode and NH3 mode,respectively.The flow rate of gas was also optimized.Finally 0.4 mL/min of NH3 was selected as the reaction gas.At this time,the BEC of Cd in 1000μg/mL Mo standard solution was about0.8 ng/L,indicating that the interference of multi-atomic ions such as molybdenum-oxygen and molybdenum-nitrogen could be effectively eliminated.Under the selected instrumental conditions,the linear correlation coefficient of calibration curve was higher than 0.999 9,the detection limit of method was 2.7 ng/g,and the recoveries were between 93%and 105%.The determination method of trace cadmium in high-purity molybdenum by inductively coupled plasma tandem mass spectrometry was established.The proposed method was applied for the analysis of high-purity molybdenum samples.The relative standard deviations（RSD,n=5）of measured results were between 0.50%and 4.2%.