ICP-MS has several attractive features compared with other analytical techniques including high sensitivity, rapid elemental analysis, wide dynamic range and isotopic information. However, when a sample which contains high matrix is introduced, polyatomic ions and isobars due to matrix might interfere with the analytes and make the analysis difficult. In order to overcome such kinds of interferences, several techniques such as internal standard correction and doubly charged ion measurement were reported. In this study, chromatographic technique was used to separate a matrix. Ion chromatoanalyzer (IC 7000, Yokogawa analytical systems Inc.) was connected to ICP-MS (HP 4500, Hewlett-Packard Company) directly. The time charts of 12 rare earth elements (REEs) from Y (m/z=89) to Lu (m/z=175) in 1000 mg/L (ppm) Ce₂O₃ are shown. Without matrix separation, the polyatomic ions duo to Ce overlap some isotopes of other REEs. With ion chromatography, Ce, i.e. the polyatomic ions due to Ce, and other REEs can be separated clearly. Another feature of ICP-MS combined with chromatographic technique, speciation analysis will also be presented.