三重四极杆电感耦合等离子体质谱法测定K417合金中痕量硒和镉

K417合金中痕量Se和Cd的存在会严重影响其机械性能以及耐用性,因此准确测定其含量至关重要。采用电感耦合等离子体质谱法(ICP-MS)测定时,存在如⁶⁴Ni¹⁶O⁺对⁸⁰Se⁺以及⁹⁵Mo¹⁶O⁺对¹¹¹Cd⁺等质谱干扰,从而影响测定结果。实验采用盐酸-硝酸-氢氟酸在沸水浴中加热溶解样品,在三重四极杆(MS/MS)充O₂反应模式下,先分别设置一级质量过滤器(Q1)的质荷比(m/z)为80和111;再在碰撞反应池(CCT)中通入反应活性较大的O₂,将⁸⁰Se⁺、⁹⁵Mo¹⁶O⁺、⁹⁴Zr¹⁶O¹H⁺等与O₂反应生成⁸⁰Se¹⁶O⁺、⁹⁵Mo¹⁶O¹⁶O⁺、⁹⁴Zr¹⁶O¹⁶O¹H⁺,而⁶⁴Ni¹⁶O⁺、¹¹¹Cd⁺等不与O₂反应;最后设置二级质量过滤器(Q2)的质荷比分别为96和111,利用质量转移法(Mass shift)和原位法(On mass)使⁸⁰Se¹⁶O⁺、¹¹¹Cd⁺通过并被检测,从而避免了质谱干扰。据此,建立了三重四极杆电感耦合等离子体质谱法(ICP-MS/MS)测定K417合金中Se和Cd的方法。对O₂流量进行了优化,分别选择O₂流量为0.3 mL/min时测定Se和0.9 mL/min时测定Cd,同时在内标溶液中加入6%(体积分数)的异丙醇作为基体改进剂以提高试验的灵敏度和稳定性。Se的线性范围为0.018~100.0 μg/L,Cd为0.001~5.0 μg/L,线性相关系数均为0.999;Se和Cd的检出限分别为0.018 μg/g和0.000 8 μg/g,定量限分别为0.058 μg/g和0.002 7 μg/g。按照实验方法对高温合金标准物质中Se和Cd进行测定,测定结果与认定值一致。对K417合金样品中Se和Cd进行测定,测定结果与辉光放电质谱法相一致,其相对标准偏差(RSD,n=6)分别为2.2%和14.9%。

Determination of trace selenium and cadmium in K417 alloy by triple quadrupole inductively coupled plasma mass spectrometry

The presence of trace selenium (Se) and cadmium (Cd) in K417 alloy can severely affect its mechanical property and durability. Therefore, the accurate determination of Se and Cd contents is of great significance. During the determination of Se and Cd by inductively coupled plasma mass spectrometry (ICP-MS), the interference of ⁶⁴Ni¹⁶O⁺ with ⁸⁰Se⁺ and ⁹⁵Mo¹⁶O⁺ with ¹¹¹Cd⁺ will influence on the determination results. In experiments, the sample was dissolved with hydrochloric acid-nitric acid-hydrofluoric acid in boiling water bath. The mass-to-charge ratio (m/z) of the first-order mass filter (Q1) was set as 80 and 111 at the reaction mode of triple quadrupole (MS/MS) filling with O₂. Then O₂ with high reactivity was injected into collision/reaction cell (CCT). ⁸⁰Se⁺, ⁹⁵Mo¹⁶O⁺ and ⁹⁴Zr¹⁶O¹H⁺ could react with O₂ to form ⁸⁰Se¹⁶O⁺, ⁹⁵Mo¹⁶O¹⁶O⁺ and ⁹⁴Zr¹⁶O¹⁶O¹H⁺, respectively. Meanwhile, ⁶⁴Ni¹⁶O⁺ and ¹¹¹Cd⁺ could not react with O₂. Finally, the m/z of the second-order mass filter (Q2) was set as 96 and 111, respectively. ⁸⁰Se¹⁶O⁺ and ¹¹¹Cd⁺ were passed and detected by the mass shift method and on mass method, which avoided the mass spectrum interference. Based on these results, a method for the determination of Se and Cd in K417 alloy by triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS/MS) was established. The flow rate of O₂ was optimized and selected at 0.3 mL/min for Se and 0.9 mL/min for Cd, respectively. Meanwhile, 6% (volume fraction) isopropanol was added into internal standard solution as the matrix modifier to enhance the experimental sensitivity and stability. The linear range was 0.018-100.0 μg/L for Se and 0.001-5.0 μg/L for Cd. The linear correlation coefficients were 0.999. The limit of detection for Se and Cd was 0.018 μg/g and 0.000 8 μg/g, and the limit of quantification was 0.058 μg/g and 0.002 7 μg/g, respectively. The contents of Se and Cd in certified reference material of high temperature alloy were determined according to the experimental method, and the found results were consistent with the certified values. The contents of Se and Cd in K417 alloy sample were determined, and the found results were basically consistent with those obtained by the glow discharge mass spectrometry (GD-MS). The relative standard deviation (RSDs, n=6) was 2.2% and 14.9%, respectively.