Chromatography with Supercritical Fluids

Abstract

Chromatography with supercritical fluids unites the features of both gas chromatography and liquid chromatography, yet retains special characteristics of its own. The diffusion coefficient and particularly the viscosity of fluid phases may approach values for low‐pressure gases, while the solvent power may be similar to that of liquids. However, with supercritical fluids it is possible to control chromatographic separations very effectively by pressure programming, since the solubility increases with increasing density. Temperature programming, on the other hand, can have the opposite effect to that in gas‐ or liquid‐chromatography since the density decreases with increasing temperature at a given pressure. Supercritical fluid chromatography is primarily of interest for the separation of higher molecular weight compounds. The efficiency of this method of separation is demonstrated on several homologous series. Thus, a styrene oligomer with nominal Mw=2200 can be resolved by a pressure and temperature program into 40 species.

Modification of Butter Oil by Extraction with Supercritical Carbon Dioxide

“…8 and 9. Consequently, we applied a column of silica gel, which is the most popular adsorbent for lipid fractionation, to remove the cholesterol from triglycerides in the extracted butter oils according to the principle of supercritical fluid chromatography, 21) which has been demonstrated to be efficient in frac-,tionating various organic compounds. The usage of a column of adsorbents such as activated charcoal and alumina has already 0, using 60 g of silica gel; .…”

Fundamental Studies and Applications of Supercritical Fluids

“…Additional work has appeared on Xe, SF 6 , C^, and NH 3 (24,25). For all fluids, spectral shifts were observed with fluid density.…”

“…However, if a substance is heated and maintained above its critical temperature it becomes impossible to liquify it with pressure (1). When pressure is applied to this system a single phase forms that exhibits unique physicochemical properties (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). This single phase is termed a supercritical fluid and is characterized by a critical temperature and pressure (T c and P c ).…”

“…io- 2 Because of their unique characteristics, supercritical fluids have received a great deal of attention in a number of important scientific fields (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). Several reasons are given for choosing a supercritical fluid over another solvating system, but choice is governed generally by: 1) the unique solvation and favorable mass transport properties (5) and 2) the ease with which the chemical potential can be varied simply by adjustment of the system pressure and/or temperature (13).…”

New Methods for Characterization of Supercritical Fluid Solutions

“…The advantages of supercritical fluid chromatography (SFC) accrue from the nature of supercritical fluids. The solvating properties of supercritical fluid mobile phases approach those of liquid phases, yet solute diffusivity typically remains one to two orders of magnitude higher [13]. These properties allow high separation efficiencies to be realized while exploiting the variable and sometimes high solvating power of the supercritical fluid.…”