Evaluation of a microwave-induced plasma in helium at atmospheric pressure as an element-selective detector for gas chromatography

Abstract

The analytical performance of a microwave-induced plasma (MIP) generated at 2450 MHz in helium at atmospheric pressure with a cavity of novel design was evaluated for carbon, hydrogen, sulphur, chlorine, bromine and iodine. Detection limits, relative sensitivities, selectivities, and linear ranges are reported. The detection limits attained with this MIP are considerably improved compared with those reported in the literature for helium MIP's at reduced pressure and the argon MIP at atmospheric pressure. Spectral characteristics of the various MIP's are compared and an attempt is made to explain the differences in terms of the different energy requirements of the respective excitation processes. The energies of the excited states of the analytes and the energy of molecular helium are critically examined.