电感耦合等离子质谱仪取样锥后分析离子空间传递行为的探讨

Discussion on the space transfer behavior of analysis ion after sampling cone of inductively coupled plasma mass spectrometer

为更好的理解困扰电感耦合等离子质谱仪(ICP-MS)分析灵敏度提高的基质干扰问题,利用激光诱导荧光技术,考察了钡离子和钙离子在ICP-MS取样锥后的质量控制传递行为。通过比较分析离子在取样锥孔口及后端的径向分布,探讨了ICP功率、雾化气流速及基质干扰对取样锥后分析离子空间分布的影响。结果表明:取样锥孔口钙离子与钡离子分布类似,但取样锥后扩散状况与其相对原子质量有关,相对原子质量小的元素径向扩散更快,因此仪器检测灵敏度较低;雾化气流速越大,分析离子的传递效率越低,因此更高的进样速率在ICP-MS应用中不一定对应更高的检测灵敏度;分析离子径向分布及数量也受基质组分影响,基质干扰降低了取样锥后中心轴线上的分析离子数量,使其径向分布变得更扁平,通过截取锥的概率更低,最终使得分析离子的信号降低。

The improvement of analytical sensitivity of inductively coupled plasma mass spectrometer （ICP- MS） was affected by the matrix interference. In order to better understand this problem, the mass control transfer behaviors of barium and calcium ions after sampling cone of ICP-MS were investigated by laser in- duced fluorescence technology. The radial distribution of analysis ion at and after sampling cone was com- pared. The influence of ICP power, atomization gas flow and matrix interference on the spatial distribution of analysis ion after sampling cone was discussed. The results showed that the distribution of calcium and barium ions at sampling cone was similar. However, the diffusion behavior after sampling cone was related to relative atomic mass. The element with smaller relative atomic mass exhibited faster radial diffusion, so the detection sensitivity of instrument was lower. The higher atomization gas flow was, the lower the transfer efficiency of analysis ion was. Therefore, the higher sampling rate may not correspond to the higher detection sensitivity in ICP-MS application. The radial distribution and the number of analysis ion was also affected by the matrix. Meanwhile, the number of analysis ion in central axis after sampling cone was reduced by the matrix interference. As a result, the radial distribution became more flat, and the probability passing through the skimmer cone was lower, which finally decreased the signal of analysis ion.