Super-critical fluid chromatography

Another growing technique is super-critical fluid chromatography. Recent references to soil analysis include the following applications aliphatic hydrocarbons, polyaromatic hydrocarbons, polychlorobiphenyls, dioxins, alkyl and aryl phosphates, chloro, organophosphorus, triazine, substituted urea, phenoxy acetic acid, Dacthal herbicides and insecticides and mixtures of herbicides and pesticides and mixtures of organic compounds. 

M. Di Maso, W. C. Purdy, S. A. McClintock, and M. L. Cotton, Determination of sorbitan trioleate in metered-dose inhalers by super- critical-fluid chromatography, J. Pharm. Biomed. Anal., 5 303 (1990). 

CSP = chiral stationary phase SMBC = simulated moving bed chromatography HPLC = high-performance liquid chromatography MPLC = medium pressure liquid chromatography SFC = super-critical fluid chromatography. 

The feed injection is performed by an injection loop. Advantage of this method is that the loop can be filled during the elution of the column, so the accuracy of the injection can be combined with a single flow rate purification method. This method is the only way to perform the injection of crude material in a one-column steady-state recycling system. It is also the most suitable injection method in super critical fluid chromatography. The main drawback of this method is that... 

The basic concepts have already been presented in this review. However, the study of single compounds does not require an interface between the chromatographic unit and the MS. The analysis of mixtures by MS relates not only to GC/MS or HPLC/MS . The popularity of GC/MS systems can be examined by the nuihber of relevant publications. These were less than 100 in 1968, rose to a peak of 2000 papers in 1979, dropped to 1500-1750 yearly until 1988, when they rose again to 2000. The use of MSD for HPLC (also called LC/MS) also rose from a few publications in 1975 to a few hundred in 1988. A method, less used for hydrocarbon analysis, SFC (Super-critical Fluid Chromatography)/MS, was initiated only in 1985 and is gaining interest slowly. These data are given by Evershed . Obviously it will be impossible to review all these developments in the use of MSD ", even for the analysis of alkanes and cycloalkanes. 

Macaudiere P, Caude M, Rosset R, Tambute A (1987) Chiral resolution of racemic amides and phosphine oxides on a P-cyclodextrin-bonded stationary phases by super critical fluid chromatography. J Chromatogr 405 135-143... 

Spectro- photometry Lumines- Infrared cence spectroscopy HPLC Super critical fluid chroma- tography GLC GLC-m/s Pyrolysis ESR GLC Thin layer chromatography... 

Achiral (separation of diastereomeric derivatives) and chiral (sepa-ration of enantiomers) chromatography gas chromatography high-performance liquid chromatography super- and sub-critical fluid chromatography thin-layer chromatography... 

D. E. Martire, Unified theory of adsorption chromatography with heterogeneous surfaces gas, liquid and super-critical fluid mobile phases , J. Liq. Chromatogr. 11 1779-1807(1988). 

Supercritical fluid chromatography, SFC a super critical fluid is produced when a gas, e.g. carbon dioxide is maintained above its critical pressure (73 atm) and temperature (3rC). The super critical fluid is used as the mobile phase with GC like capillary columns or HPLC reverse phase columns and a flame ionisation or flame photometric detector. 

The general confusion about the physical and chemical meaning of the words super and critical has lead to a plethora of terms such as subcritical fluid chromatography, near-critical fluid chromatography, and enhanced fluid chromatography to deal with the fluids when they are nearly but not quite super critical. All these names, including SFC, actually describe the same technique. 

One variant, close to LC, that has been successfully interfaced to infrared spectroscopy, is supercritical fluid chromatography (SFC). In this case, one of the key mobile phases, super critical carbon dioxide, is virtually transparent for most of the mid-IR region. This may be operated directly on-line with a high-pressure liquid flow cell. 

Supercritical fluid chromatography (SEC) refers to the use of mobile phases at temperatures and pressures above the critical point (supercritical). SEC uses carbon dioxide as a main component in the mobile phase because its critical point (31.3°C, 7.39 MPa) is easy to reach. However, carbon dioxide is similar to alkanes in solvent strength and therefore unsuitable for the elution of polar compounds. This character is corrected by the addition of a significant amount of polar solvents, mainly alcohols, to increase the polarity of the mobile phase. In such conditions, the supercritical state is not actually reached. Often temperatures lower than the critical and pressure above the critical are applied. These are designated as subcritical conditions. Nevertheless, separations are performed indistinctively in super- or subcritical conditions. 

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