Our ICP-MS (Perkin Elmer Nexion 350D) allows three modes of operation.
No cell gas is used and the instrument works as a non-cell instrument, a mode for elements not requiring interference correction and often used for Laser Ablation.
A non-reactive gas such as Helium is introduced into the Universal Cell cell to collide with interfering ions with larger diameters, affecting their kinetic energy to be removed through Kinetic Energy Discrimination.
A highly reactive gas such as Ammonia is introduced into the cell to create predictable chemical reactions with the interferences or the analyte ions (oxide mass shifting). The interferences or side reactions are removed by a scanning quadrupole so only the element of interest is passed to the quadrupole and detector.