A capillary supercritical fluid chromatograph (SFC) was coupled to a surface-wave-sustained microwave-induced plasma (MIP) sustained with a surfatron. The chromato-
A microwave-induced plasma (MIP) sustained In helium Is evaluated as an element-selective detector for capillary supercritical fluid chromatography (SFC). The plasma source, a surface-mlcrowave-lnduced plasma (surfatron), Is described. Optimal plasma conditions Including viewing position, helium flow rate, and applied microwave power are discussed for sulfur emission In the near-infrared spectral region. In addition, the effects of two common mobile phases (C02 and N20) on plasma stability, sensitivity, and spectral background from 200 to 1100 nm are assessed. Although the plasma was evaluated principally for use with SFC, much of the discussion Is relevant to Its application as a gas chromatographic detector.Capillary gas chromatography (GC) and capillary liquid chromatography (LC) possess inherent liabilities that make them unsuitable for many types of separations. The former is ultimately restricted by the limited volatility and thermal lability of many organic compounds. The latter is restricted
A relatively new detection method for ion chromatography (IC) called replacement-Ion chromatography (RIC) Is critically evaluated. The capabilities and limitations of cationreplacement RIC for cation and anion separatlon and determination were explored by uslng a conventlonal dual-column IC system followed by a continuously regenerating Nafion cation-exchange fiber (the replacement column). This third cdumn converts all lonk solutes into their lithium salts, whlch are detected by an acetylene-air flame-emission spectrometer. Although poor figures of merit were observed for cation chromatography, the method is analytically useful for anion chromatography. Anlon detection llmits are 3-50 ng and depend upon the replacement-Ion background produced by the eluent. This background llmitatlon of RIC and the infiuence of varlous system parameters are dlscussed in detail.
Emission spectra in the UV-visible and near-infrared (NIR) spectral regions are presented for several nonmetals introduced as aqueous solutions by a glass-frit nebulizer. Detectability improves dramatically for some nonmetals with the use of a desolvation system to reduce the amount of water vapor entering the plasma. Detection limits for P, I, S, Cl, Br, and C are in the low- to sub-ppm range. Good precision (RSD <5%) and a dynamic range of 2–3 decades were observed for I and P. Easily ionizable elements such as K, Na, and Li can enhance nonmetal emission by as much as 30%.
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