Fundamental aspects of ion extraction in inductively coupled plasma mass spectrometry

The present understanding of the ion extraction process in inductively coupled plasma mass spectrometry (ICP-MS) is reviewed critically. Topics include ion production in the ICP, origins of polyatomic ions, causes of and remedies for the secondary discharge, properties of the supersonic jet and of the beam leaving the skimmer, space charge effects, and matrix interferences. Areas of recent interest are also described from the perspective of the ion extraction process. These recent topics include ''cool'' plasmas, the three-aperture interface, ion extraction from helium plasmas, and ion sampling considerations unique to magnetic sector, time-of-flight, and ion trap mass spectrometers.