a system and method for separating ions in an ion mixture , such as a plasma in space . the ion mixture enters an electrostatic analyzer , whose ion path has at least two sections . a first section applies a dc voltage to the ions , and a next section applies an rf frequency voltage to the ions . appropriate dc and rf voltages are applied , such that at least a portion of the lower mass ions are absorbed into the rf section of the analyzer . the heaver ions are transmitted out of the ion path and are readily available for further analysis .