INDUCTIVELY COUPLED PLASMA MICROWAVE-INDUCED PLASMA TANDEM SOURCE FOR ATOMIC EMISSION-SPECTROMETRY

A tandem source has been constructed by linking an atmospheric-pressure inductively coupled plasma (ICP) with a reduced-pressure microwave induced plasma (MIP). An aerosol of sample solution is introduced into the ICP where it is vaporized and atomized. The resulting analyte atoms are then extracted from the ICP, through a sampling orifice and into a moderate-pressure region in which a microwave discharge is supported by a Beenakker-type resonance cavity. It is from this latter discharge that analyte atomic or ionic emission is viewed. This paper examines the analytical characteristics of this pressure-differential tandem source, including optimization studies, background spectra and intensity, noise features, chemical interferences, linear range and detection limits. Experimental results indicate that this novel arrangement provides some of the expected benefits of a tandem source while other figures of merit are only of the same order of magnitude as results obtained by conventional ICP atomic emission spectrometry. Unfortunately, it is found that the microwave plasma adds more background than signal at many elemental emission lines.