Measurement of gas kinetic temperatures for polyatomic ions in inductively coupled plasma-mass spectrometry: Validation and refinements

The general method of comparing measured ion ratios to calculated ion ratios to determine a gas kinetic temperature (Tgas) is reviewed. Various mathematical refinements to the calculated partition functions are examined for their effect on the determined Tgas. It is found that (a) excited electronic states should be included for ArO+, neutral NO, and O2; (b) a 10% error in solvent load, sample gas flow rate, vibrational constant (ω), rotational constant (B) or measured ion ratio produces only a 1 to 3% error in Tgas; (c) a 10% error in dissociation energy (D0) creates nearly a 10% error in Tgas; and (d) high temperature corrections to the partition functions produce minimal change and can generally be neglected.