Temporally and spatially integrated measurements of the intensities of a number of atomic and ionic lines of several elements (Cr, Mn, Mg, Co, Fe, Cd and Zn) were used to calculate their degree of ionization in He, Ar and He-Ar mixed gas plasmas in a radiofrequency (rf) furnace atomization plasma emission spectrometry (FAPES) source. The effects of rf power and plasma gas flow rate were also investigated. The emission intensities of ionic and atomic lines and the degree of analyte ionization are enhanced as Ar is added to the He plasma. Maximum degrees of ionization of 99, 80, 81, 72, 76, 12 and 38% for Cr, Mn, Mg, Co, Fe, Cd and Zn, respectively, were obtained in pure Ar. The mechanism of analyte ionization and excitation is discussed.