The origin of certain polyatomic ions in inductively coupled plasma mass spectrometry is investigated. Ion ratios are predicted with the use of partition functions and compared to mass spectrometric measurements. It is found that the simple models for the predicted ratios work well compared to more complex formulations. Cone material and geometry is found to have the most effect on ArX⁺ species. Potential energy curves for ArO⁺ are examined. It is determined that ArO⁺ is best described when a Boltzmann distribution between the first two electronic energy levels is not followed. Analyte metal oxide memory was investigated and found to originate from deposits on the skimmer cone.