ICP-QMS uses a plasma of the same type as in ICP-AES, but here it is used to ionize the atoms of the elements, i e to make them electrically charged. The charged particles (ions) are then separated by mass in a mass spectrometer. This allows the different elements in a sample (and their natural isotopes) to be separated and their concentrations determined. The core of the ICP-MS system is the interface through which ions from the plasma enter the high-vacuum chamber of the mass spectrometer.