Formation of doubly charged atomic ions in the inductively coupled plasma

Experimental and theoretical studies dealing with the formation efficiency of M²⁺ ions, which reduce the analytical signal of M⁺ ions and cause spectral interferences in the inductively coupled plasma mass spectrometry (ICP-MS), have been discussed. Inconsistencies in the results have been pointed out and goals have been formulated for further investigations necessary to correct those spectral interferences. The range of elements that form most readily M²⁺ ions has been determined. Partition functions and reduced thermodynamic potentials of atoms, M⁺ and M²⁺ ions of elements with the lowest second ionization potentials have been calculated. The Saha equation and the thermodynamic simulation were used to calculate the formation efficiency of M⁺ and M²⁺ ions for a selected group of elements in ICP. The results have been compared with experimental and theoretical data available in the literature. The accuracy of the calculations and their applicability to the prediction of the formation efficiency of M⁺ and M²⁺ ions in ICP and other spectral sources has been demonstrated. The main factors responsible for the disagreement between experimental and theoretical values of the formation efficiency of M⁺ and M²⁺ ions have been determined.