Monoxide Ion Signals in Inductively Coupled Plasma Mass Spectrometry

Abstract

The ion signals of oxide-forming elements (M⁺) and their monoxides (MO⁺) have been investigated as functions of inductively coupled plasma operating parameters. An appropriate selection of the radio frequency power, carrier-gas flow rate and sampling depth was essential in order to minimize the signal ratio, S_MO(+)/S_M(+). Signals S_MO(+) and S_M(+) decreased drastically with increasing radial distance from the plasma center. The signal ratios S_MO(+)/S_M(+) for various analytes, in consideration of partition functions and mass numbers, showed a linear relation with the oxide dissociation energies. Equivalent concentration data are also given for typical oxide interferences.