Comparison of a very high frequency 148 MHz inductively coupled plasma to a 27 MHz ICP

Physical parameters and analytical performance are determined for an analytical ICP operated at 148 MHz, a frequency nearly three times higher than any previously reported. The iron(I) excitation temperatures are approximately 1.5 times lower and the electron densities are five times lower than at 27 MHz. The consequences of these changes are lower analyte and background continuum emission intensities, such that the signal to background ratios are decreased at the higher frequency. Freedom from interferences and working curve linearity are unaffected while ease of sample introduction is improved. A shift towards atomic emission indicates a deviation farther from LTE at 148 MHz. These effects are attributed to the decrease in skin depth with increasing frequency.