1引言火花源质谱法有较高的质量分辨能力和很高的灵敏度．对于象Ce、Pr等同位素较少的元素由于谱线干扰较小，通过加入内标和相对灵敏度因子方法便可进行定量分析．我们选择了最适宜的操作条件和大曝光及多内标元素方法，成功地直接测定纯度为99.999％～99．9999％的高纯CeO2和 1 Introduction Spark mass spectrometry has a higher quality of resolution and high sensitivity. For elements such as Ce and Pr which have fewer isotopes, they can be quantitatively analyzed by adding an internal standard and a relative sensitivity factor due to less spectral interference. We chose the most appropriate operating conditions and large exposure and multiple internal standard methods, the direct determination of the purity of 99.999% to 99.9999% purity of CeO2 and