Supercritical fluid technology mobility

In supercritical fluid chromatography, fluids above their critical point are used as mobile phases. This chapter discusses the principles of operation, mobile phase considerations, parameters that can be adjusted in method development as well as an overview of instrumentation required and a few pertinent examples from current literature. Not everything can be illustrated, but the advantages of this diverse technology will be highlighted. 

Capillary Columns for SFC-MS. At present, the major limitation to broad application of capillary SFC technology is related to the availability of columns compatible with supercritical fluid mobile phases. The fused silica capillary columns used in this work were deactivated and coated with crosslinked and surface-bonded stationary phases using techniques similar to those reported by Lee and coworkers (40,41). Columns from less than 1 m to more than 20 m in length and with inner diameters of 10 to 200 ym have been examined. Colvimn deactivation was achieved by purging with a dry nitrogen flow at 350 C for several hours followed by silylation with a polymethylhydrosiloxane. Any unreacted groups on the hydro-siloxane were capped by treatment with chlorotrimethylsilane at 250 C. After deactivation, the columns were coated with approximately a 0.15-.25 ym film of SE-54 (5Z phenyl polymethylphenyl-siloxane) or other polysiloxane stationary phases. The coated stationary phases were crosslinked and bonded to the deactivation layer by extensive crosslinking with azo-t-butane (41). The importance of deactivation procedures for elution of more polar compounds, such as the trichothecenes, has been demonstrated elsewhere (42). 

The SFC technique is closely related to HPLC, using much the same kind of hardware but with compressed gas such as CO2 as a major component in the mobile phase. Therefore the solvent volume of the purified fraction of the desired product is very small and easily removed, which increases the productivity significantly. More recently supercritical-fluid chromatography (SFC) has begun to show promise as a good technology for purification of the combinatorial library. The technique and applications of SFC are reviewed by several authors. ... 

An essential role in the implementation of GCE in MSU is played by the Moscow University Supercritical Innovation Center, MUSIC (Head, Prof. V. Lunin Scientific Sectetary, Prof. S. Vatsadze). The main goal of MUSIC is the training of high-quality specialists in the use of supercritical fluids (ScF) for research laboratories, performing the study of fundamentals and developing new ScF technologies. The instrumentation of MUSIC includes a unique mobile ScF set with a high-pressure cell equipped with an inspection window, four stationary sets with a united control centre as well as a flow-type device. 

Supercritical Fluid Chromatography (SFQ and Supercritical Fluid Extraction (SFE) A separation technology similar to other extraction and chromatographic methods, but in which the mobile phase is actually a fluid in its supercritical fluid state. A supercritical fluid is a fluid that is held above its critical temperature and pressure, and for which no application of additioncJ pressure can result in the development of a liquid phase. Supercritical fluids are unique in that while they possess liquid-like densities, the mass transfer behavior is superior to that of liquids. Supercritical fluid chromatography remains a niche method that is applicable to pharmaceuticals and other high relative molecular mass solutes. Supercritical extraction, on the other hand, is more widely used as a sample preparation method, especially in pharmaceutical analyses, polymers, and environmental analyses. 

---