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 (T_gas) is reviewed. Various mathematical refinements to the calculated partition functions are examined for their effect on the determined T_gas. 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 T_gas; (c) a 10% error in dissociation energy (D₀) creates nearly a 10% error in T_gas; and (d) high temperature corrections to the partition functions produce minimal change and can generally be neglected.