Evaluation of a microwave cavity, discharge tube, and gas flow system for combined gas chromatography-atomic emission detection

A review is presented on the historical, fundamental, and practical aspects of microwave-induced plasmas (MIP) and their application to spectrochemical analysis. In particular, the mechanism of formation and stabilization of a microwave discharge is explored and possible excitation processes involving analyte atoms are described. Conditions under which a MIP can be operated are delineated and instrumentation necessary for MIP spectroscopy is described in detail. Methods for sample introduction into a MIP are reviewed and evaluated critically and the performance of MIP sources in real sample determinations is evaluated. Overall, the MIP appears to be a highly promising and under-utilized source in atomic spectrometry.

Microwave-Supported Discharges:

Interfacing of fused silica gas chromatographic capillary columns to a microwave-excited atmospheric pressure helium plasma (MED) is investigated. The system for glass and fused silica capillary operation incorporates an interface where excess solvent can be vented by a chemically deactivated fluidic-logic gas switching system. A TM/sub 010/ resonant cavity allows axial viewing of plasma emission. A quartz refractor plate background corrector improves selectivity ratios for elements whose emission occurs in the high-carbon (cyanogen) background region. Background emission characteristics of the helium plasma under various conditions are established from 200 to 500 nm. Calibration curves, selectivity ratios, and detection limits are established for the elements vanadium, niobium, chromium, molybdenum, tungsten, manganese, iron, ruthenium, osmium, cobalt, nickel, mercury, boron, aluminum, carbon, silicon, germanium, tin, lead, phosphorus, arsenic, sulfur, selenium, fluorine, chlorine, bromine, iodine, hydrogen, and deuterium.

Microwave-excited atmospheric pressure helium plasma emission detection characteristics in fused silica capillary gas chromatography

Atmospheric pressure helium microwave detection system for gas chromatography

The use of a halocarbon/argon atmosphere in the sampling manifold of a graphite rod electrothermal vaporization device employed for the introduction of samples into a high-frequency, inductively coupled argon plasma source for optical emission spectroscopy is shown to permit sensitive determination of elements such as boron, molybdenum, zirconium, chromium, and tungsten which form refractory oxides or carbides which limit attainable sensitivity when an argon atmosphere alone is employed. Typical improvements in the detection limits obtained with this technique are between one and two orders of magnitude, so that subnanogram amounts of these elements may be detected; linear dynamic concentration ranges of four orders of magnitude have been obtained with the procedure employed. 2 figures, 3 tables.

Volatilization of refractory compound forming elements from a graphite electrothermal atomization device for sample introduction into an inductively coupled argon plasma

P.W.J.M. Boumans

Papers

Additional experience with the cylindrical TMO010 cavity for generating an MIP in helium and argon at atmospheric pressure