29: Supercritical Fluid Chromatography
- Page ID
- 333382
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Although there are many analytical applications of gas chromatography and liquid chromatography, they can not separate and analyze all types of samples. Capillary column GC separates complex mixtures with excellent resolution and short analysis times. Its application is limited, however, to volatile analytes or to analytes made volatile by a suitable derivatization reaction. Liquid chromatography separates a wider range of solutes than GC, but the most common detectors—UV, fluorescence, and electrochemical— have poorer detection limits and smaller linear ranges than GC detectors, and are not as universal in their selectivity. For some applications, supercritical fluids provide an attractive solution to these limitations.
- 29.1: Properties of Supercritical Fluids
- A supercritical fluid is a species held at a temperature and a pressure that exceeds its critical point. Under these conditions the species is neither a gas nor a liquid. Some properties of a supercritical fluid are similar to a gas; other properties, however, are similar to a liquid. The viscosity of a supercritical fluid is similar to a gas; THE density of a supercritical fluid, on the other hand, is much closer to that of a liquid, which explains why supercritical fluids are good solvents.
- 29.2: Supercritical Fluid Chromatography
- The instrumentation for supercritical fluid chromatography essentially is the same as that for a standard HPLC. The only important additions are a heated oven for the column and a pressure restrictor downstream from the column to maintain the critical pressure.