An analytical technique was developed by a combination of single particle dissolution, chemical separation of uranium, plutonium and americium with extraction chromatography using UTEVA resins and measurement with inductively coupled plasma mass spectrometry. This method was applied to plutonium isotope ratio analysis of individual U-Pu particles with U/Pu ratios ranging from 1 to 70. Consequently, Pu-240/Pu-239, Pu-241/Pu-239 and Pu-242/Pu-239 isotope ratios were successfully determined, while it was impossible to determine Pu-238/Pu-239 ratios due to the high process blank values on m/z 238.