Examination of a helium highly efficient microwave-induced plasma as an element-selective detector for supercritical fluid chromatography

Abstract

The use of a highly efficient microwave-induced plasma as an element-selective detector for packed column supercritical fluid chromatography is discussed. The cavity is able t o support an Ar or He discharge at powers of 150 W or less. The effects of the introduction of supercritical C 0 2 on the analytical parameters of the plasma are described and minimum detectable quantity values for S, P and CI are presented.

Atomic emission detection for supercritical fluid chromatography using a moderate-power helium microwave-induced plasma

“…Though more sensitive when common elements are compared than the previous work in packed column SFC-MIP (5), the detection limits are not as sensitive as those reported with capillary column SFC-MIP systems (1, 3,4). The previous packed column work used UV-vis emission lines.…”

“…The first planar waveguide sensors to be developed were based upon attenuation of the guided beam (absorption spectrometry) (2-4). Interest in these sensors waned with the development of inexpensive fiber components until the early 1980s when planar waveguides were "rediscovered" for applications in Raman spectroscopy (5,6). Applications of planar waveguides to absorption spectrometry are continuing (7)(8)(9)(10)(11) and planar waveguide fluorescence techniques are currently under investigation (12,13).…”

“…Initial successes have been demonstrated coupling supercritical fluid chromatography (SFC) to low-power (40-150 W) helium plasma detectors (1)(2)(3)(4)(5)(6)(7)(8). Non-metal element selective detection has been achieved for both capillary (1, 3, 4) and packed column (5, 7) SFC systems.…”

“…Unfortunately, though successful as initial studies, the low-power systems have had their drawbacks. It has been shown that the SFC mobile phase causes increases in detection limits (3) and decreases in analyte line emission intensity (2,4,6-8) and signal-to-noise ratios (5). Previous work has also cited impedance tuning problems (1, 5) with SFC pressure increases.…”

Supercritical fluid chromatography and extraction

“…When N20 was used as the mobile phase, universal detection of organic species was possible by monitoring the carbon signal. Motley et al presented a series of papers describing various practical aspects of MIP detection for packed-column SFC (197)(198)(199). They first studied the effects of C02 and methanol-modified C02 on plasma performance (197).…”