电感耦合等离子体质谱法测定土壤样品中的痕量硒元素

随着电感耦合等离子体质谱技术的发展,准确测定环境样品中的痕量硒元素含量越来越受到关注。质量数76、78、80和82的硒元素受氩的多原子干扰非常严重,必须进行校正才能得到满意的结果。利用动态反应池模式对土壤样品的测定条件进行条件优化,将Cell Gas从0.3～0.7ml/min步幅0.1ml/min、RPQ从0.45～0.7步幅0.05进行同步优化,最终确定针对消解样品的Cell Gas为0.5ml/min,RPQ为0.45,78Se是最佳的测定同位素。通过石墨电热赶酸仪赶酸,适当稀释控制可溶性固体量,在线加入103Rh内标来克服基线漂移,提高了分析方法的准确性。2%甲醇的加入提高了硒在电感耦合等离子体中的离子化强度,在一定程度上增强了低浓度的响应值。根据国家标准参考物质的分析结果评价方法的准确性,证实所建立的方法简便、准确、快速。

Determination of Trace Selenium in Soils by Inductively Coupled Plasma-Mass Spectrometry

With the development of mass spectrometry, accurate determination of trace selenium in environmental attracts increasing attention. However, the elemental selenium (m/z=74, 76, 78, 80) determination encounters serious interference form argon dimmers, and a correction procedure was always needed. In this work, we adopted dynamic reaction cell (DRC) mode to optimize the analytical conditions of soil samples. The cell gas was investigated from 0.3 to 0.7 ml/min with a step of 0.1 ml/min, and simultaneously, the PRQ was tested in the range of 0.45~0.7 with a step of 0.05. For the digested samples, the best result was ⁷⁸Se in soil when Cell Gas is 0.5 ml/min and RPQ is 0.45. The intractable problem of baseline shift was also overcome via evaporation of the residual acid, appropriate dilution of the soluble substances and calibration of internal standard element, and this contributes to the improvement of accuracy. The addition of 2% methanol enhanced ionization of selenium in inductively coupled plasma. Finally, the present method was applied for analyzing standard reference materials, and the results agreed well with the certified value The experimental results showed that the proposed method was simple, fast and accurate.