Analyte ionization in a furnace atomization plasma emission source

Abstract

Temporally and spatially integrated intensities of a number of atomic and ionic lines emitted by thermometric species introduced into an rf He FAPES source were used to calculate the degree of analyte ionization. At 50 W forward power, an ionization temperature of 6025±350 K was derived from use of Cr, Mg, Fe, Co, Mn, Cd and Zn. The degree of ionization varies from 94% for Cr to 7% for Zn. Precision of determination is better than 15%. Increasing the rf power from 20 to 100 W enhances the degree of ionization by less than 50% in most cases. Addition of 0.1% (v/v) nitrogen impurity to the He plasma gas decreases the degree of ionization and is consistent with comparable enhancements in ionization noted as the He purge gas flow rate is increased, thereby yielding a cleaner plasma environment. Implications of these data for use of FAPES in both an atomic emission mode and as an ion source for mass spectrometry are discussed.