Of supercritical fluids

Example of the application of supercritical fluid chromatography to the analysis of triglycerides. (Chromatogram courtesy of Alltech Associates, Inc. Deerfield, IL). 

SCFs induction of [SUPERCRITICAL FLUIDS] (Vol23) -of soap [SOAP] (Vol 22)... 

Supercritical Extraction. The use of a supercritical fluid such as carbon dioxide as extractant is growing in industrial importance, particularly in the food-related industries. The advantages of supercritical fluids (qv) as extractants include favorable solubiHty and transport properties, and the abiHty to complete an extraction rapidly at moderate temperature. Whereas most of the supercritical extraction processes are soHd—Hquid extractions, some Hquid—Hquid extractions are of commercial interest also. For example, the removal of ethanol from dilute aqueous solutions using Hquid carbon dioxide... 

Although modeling of supercritical phase behavior can sometimes be done using relatively simple thermodynamics, this is not the norm. Especially in the region of the critical point, extreme nonideahties occur and high compressibilities must be addressed. Several review papers and books discuss modeling of systems comprised of supercritical fluids and soHd orHquid solutes (rl,i4—r7,r9,i49,r50). 

Numerous high pressure Hquid chromatographic techniques have been reported for specific sample forms vegetable oHs (55,56), animal feeds (57,58), seta (59,60), plasma (61,62), foods (63,64), and tissues (63). Some of the methods requite a saponification step to remove fats, to release tocopherols from ceHs, and/or to free tocopherols from their esters. AH requite an extraction step to remove the tocopherols from the sample matrix. The methods include both normal and reverse-phase hplc with either uv absorbance or fluorescence detection. AppHcation of supercritical fluid (qv) chromatography has been reported for analysis of tocopherols in marine oHs (65). 

TABLE 22-11 Commercial Applications of Supercritical Fluid Separations Technology... 

Transport Properties Although the densities of supercritical fluids approach those of conventional hquids, their transport properties are closer to those of gases, as shown for a typical SCF such as CO9 in Table 22-12. For example, the viscosity is several orders of magnitude lower than at liquidlike conditions. The self-diffusion coefficient ranges between 10" and 10" em /s, and binaiy-diffusiou coefficients are similar [Liong, Wells, and Foster, J. Supercritical Fluids 4, 91 (1991) Catchpole and King, Ind. Eng. Chem. Research, 33,... 

Although several other early studies were conducted using Supercritical Fluids (SFs), also termed at that time as dense gases , this field did not receive the attention it deserved during the first half century after its discovery. Even then, the small number of investigators dedicated to further explore the scientific and technological potential of supercritical fluids concentrated then efforts on industrial rather than analytical applications (9, 10). 

Unfortunately, not much experimental work has been carried out on the combination of Supercritical fluid extraction and liquid chromatography systems (43, 44). One of the reasons for this arises from the difficulties in achieving compatibility between the extraction solvent and the FC mobile phase. Baseline perturbations have been... 

ON-LINE COUPLING OF SUPERCRITICAL FLUID EXTRACTION WITH CAPILLARY ELECTRODRIVEN SEPARATION TECHNIQUES (SFE-CESTs)... 

T. Greibrokk, Applications of supercritical fluid exti action in multidimensional systems , J. Chromatogr. 703 523-536 (1995). 

X. Lou, H.-G. Janssen and C. A. Cramers, Investigation of pai ameters affecting the online combination of supercritical fluid extraction with capillai y gas cliromatogi aphy , J. Chromatogr. 750 215-226 (1996). 

M. C. Tavai es and P. M. Lan as, On-line coupling of supercritical fluid extraction with supera itical fluid cltromatogr aphy , 7. Braz. Chem. Soc. in press (2001). 

F. M. Ean as and M. A. Ruggiero, On-line coupling of supercritical fluid exti action to capillaiy column electi odriven separation techniques , J. Microcolumn Sep. 12 61-67 (2000). 

MULTIDIMENSIONAL CHROMATOGRAPHIC METHODS WHICH INVOLVE THE USE OF SUPERCRITICAL FLUIDS... 

R. M. Smith and M. D. Buifoi d, Optimization of supercritical fluid extraaion of volatile constituents from a model plant matrix , 7. Chromatogr. 600 175-181 (1992). 

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