低温加热挥发三氯氢硅-电感耦合等离子体质谱法测定三氯氢硅中痕量砷

Determination of trace arsenic in trichlorosilane by inductively coupled plasma mass spectrometry after trichlorosilane volatilization via low temperature heating

采用电感耦合等离子体质谱法(ICP-MS)常规模式测定三氯氢硅中砷时,40 Ar35 Cl+会对75 As+的信号产生严重干扰,同时若直接进行测定,大量硅基体的存在不仅会有基体效应,也会造成对采样锥、截取锥和进样系统的堵塞,这些都给ICP-MS测定三氯氢硅中痕量砷带来了难题。实验利用石墨氮气挥三氯氢硅装置在50~90℃下对液体三氯氢硅样品进行挥发处理,以体积比为1∶1∶1∶8的氢氟酸-硝酸-过氧化氢-水为混合浸取液体对挥发后的样品残渣进行浸取,解决了因大量硅基体存在而引起的问题。同时,实验采用氢气-氦气混合碰撞/反应池模式,控制混合碰撞/反应气流速为6.0mL/min,消除了40 Ar35 Cl+对75 As+的干扰,最终实现了ICP-MS对三氯氢硅中痕量砷的测定。在优化的仪器条件下,测定砷标准系列溶液,以砷信号强度值与质量浓度进行线性回归,相关系数在0.999 0以上,方法的检出限为0.01ng/g。将实验方法应用于三氯氢硅样品中砷的测定,结果的相对标准偏差(RSD,n=11)在0.71%~7.1%之间,加标回收率为87%~105%之间。分别用微量移液器准确移取1.00、15.00μL砷标准储备溶液加入到超纯三氯氢硅中,配制成砷质量分数分别为2.00、30.00ng/g的2个三氯氢硅模拟样品,按照实验方法分别对这2个模拟样品中砷进行测定,测定值与理论值基本一致,相对误差的绝对值不大于1%。

During the determination of arsenic in trichlorosilane by inductively coupled plasma mass spectrometry（ICP-MS）in normal mode,the signal of 75 As＋would be seriously interfered by 40 Ar35 Cl＋.If the sample was determined directly,the presence of much silicon matrix not only had matrix effect,but also could cause the blocking of sampling cone,skimmer cone and sampling system.All these problems brought challenges for the determination of trace arsenic in trichlorosilane by ICP-MS.The liquid trichlorosilane sample was treated by nitrogen volatilization at 50-90℃ using graphite device.The sample residue after volatilization treatment was leached with hydrofluoric acid-nitric acid-hydrogen peroxide-water mixture with volume ratio of 1∶1∶1∶8,solving the problem caused by the presence of much silicon matrix.Meanwhile,the hydrogen-helium mixing collision/reaction cell mode was used in experiments.The flow rate of mixing collision/reaction gas was controlled at 6.0 mL/min to eliminate the interference of40 Ar35 Cl＋to 75 As＋.The determination of trace arsenic in trichlorosilane by ICP-MS was finally realized.The standard series solution of arsenic was determined under the optimized instrumental conditions.The signal intensity and mass concentration of arsenic were treated by linear regression.The correlation coefficient was higher than 0.999 0.The detection limit was 0.01 ng/g.The experimental method was applied for the determination of arsenic in trichlorosilane sample.The relative standard deviations（RSD,n=11）of determination results were between 0.71% and 7.1%.The recoveries were between 87% and 105%.1.00 and 15.00μL of standard stock solution of arsenic were accurately sampled and added into hyperpure trichlorosilane using micropipettor to prepare two simulated samples.The mass fraction of arsenic was2.00 ng/g and 30.00 ng/g,respectively.The content of arsenic in these two simulated samples was determined according to the experimental method.The found results were basically consistent with the theoretical values.The absolute value of relative error was less than 1%.