Inductively coupled plasmas (ICPs) operated at atmospheric pressure are commonly used as vaporization-atomization-excitation-ionization sources in analytical atomic emission spectrometry (AES), atomic fluorescence spectrometry (AFS), and mass spectrometry (MS). Argon-supported ICP discharges exhibit several advantages for spectrochemical analysis. They provide high powers of detection and wide concentration dynamic ranges, with minimal matrix effects, and they are extremely useful for simultaneous multielement determinations. Because of ease of operation and a power requirement lower than that for other support gases such as air, nitrogen, oxygen, and hydrogen, most laboratory ICP discharges are sustained in pure argon. This relative ease of operation and reduced power requirement are partly attributed to lower thermal conductivity, lower heat capacity, and lower electrical resistivity of Ar, compared to other support gases.