What is the substance used in ICP ionization to create a hot plasma?

In Inductively Coupled Plasma (ICP) ionization, argon is the substance utilized to create a hot plasma. During the ICP process, argon gas is ionized by a radiofrequency electric field, generating a high-temperature plasma that can reach temperatures of approximately 10,000 K. This high-temperature environment is crucial for atomizing and ionizing the sample elements effectively.

Argon is preferred over other gases for several reasons. It is inert, which means it does not react chemically with the sample being analyzed, ensuring that the composition of the sample remains unchanged during the process. The stability of argon in plasma formation allows for consistent and reproducible ionization, which is essential for accurate elemental analysis in techniques such as ICP mass spectrometry and ICP optical emission spectroscopy.

Using other gases like helium, nitrogen, or oxygen would not achieve the same level of ionization efficiency or might introduce reactants that could interfere with the analysis.