Supercritical fluids conditions

M. E. Paulaitis and co-workers, eds.. Chemical Engineering at Supercritical-Fluid Conditions, Ann Arbor Science PubHshers, Mich., 1983. 

Runaway reaction or polymerization—e.g., vinyl chloride monomer (Kim-E and Reid, The Rapid Depressurization of Hot, High Pressure Liquids or Supercritic Fluids, chap. 3, in M. E. Paulaitis et al., eds.. Chemical engineering at Supercritical Fluid Conditions, Ann Arbor Science, 1983, pp. 81-100)... 

Figure 8.16 (Fluid -+- fluid) phase diagram for a near-ideal system. Reproduced with permission from W. B. Streett, Chapter 1 in Chemical Engineering ai Supercritical Fluid Conditions, M. E. Paulaitis, J. M. L. Penninger. R. D. Gray Jr., and P. Davidson, editors, Ann Arbor Science Press. Michigan, 1983.

Weber, W.J. Jr., and Young, T. M. (1997). A distributed reactivity model for sorption by soils and sediments. 6. Mechanistic implications of desorption under supercritical fluid conditions. Environ Sci. Technol., 31(6), 1686-1691. 

Paulaitis, M.E., Penninger, J.M.L., Gray, R.D, Jr. and Davidson, P. "Chemical Engineering at Supercritical Fluid Conditions" Ann Arbor Science, Ann Arbor, 1983. 

R.G. Kander and ME Paulaitis, Chemical Engineering at Supercritical Fluid Conditions, M E. Paulaitis, J. Penninger, R. Gray, P. Davidson (Eds), Ann. Arbor Science Ann. Arbor, MI, 1983 136. 

S. Sarrade, G.M. Rios, C. Perre and M. Carles, Performance of nanofiltration under supercritical fluid conditions, in Y.H. Ma (Ed.), Proceedings of the Third International Conference on Inorganic Membranes, 10-14 July 1994, Worcester, MA, p. 129. 

These phases have been prepared by polymerization of N, N -diaUyl derivatives of tartardiantide and grafted onto silica gel. As these phases are crosslinked and bonded to sihca gel, they are insoluble in organic solvents and there is no limitation regarding the choice of mobile phase. Normal mode, reversed-phase and supercritical fluid conditions have been applied. They show good mechanical stability, but the relatively high content of achiral sihca gel in these CSPs reduces their loading capacity. A few preparative separations have been reported on these two CSPs (Kromasil) [52-54], but so far they have not been widely used for preparative apphcations. 

One of the earliest reports of SFC interfaced with APCI was by Huang et al. [121]. The authors used a pin-hole restrictor to maintain supercritical fluid conditions in a packed-column (pcSFC) system. Results for a mixture of five corticosteoids were described with an injection of 25 ng of each of the components. The system was also amenable for capillary SFC/MS applications with minimum modification. Sadoun and Virelizier [122] reported an SFC interface with ESI in which a two-pump SFC and a packed column were used with the outlet directly interfaced to an ESI source of a quadrupole mass spectrometer. Also, 1-30% (v/v) of polar organic modifier (Me0H-H20 95 5) was added to CO2 mobile phase to help elute polar organic compounds. The setup was shown to allow analysis of polar organic compounds that were difficult to analyze with earlier implementations of SFC-MS with a chemical ionization interface. A recent review article is available on pcSFC-MS [123]. 

The pressure-temperature phase diagrams also serve to highlight the fact that the polymorphic transition temperature varies with pressure, which is an important consideration in the supercritical fluid processing of materials in which crystallization occurs invariably at elevated pressures. Qualitative prediction of various phase changes (liquid/vapor, solid/vapor, solid/liquid, solid/liquid/vapor) at equilibrium under supercritical fluid conditions can be made by reference to the well-known Le Chatelier s principle. Accordingly, an increase in pressure will result in a decrease in the volume of the system. For most materials (with water being the most notable exception), the specific volume of the liquid and gas phase is less than that of the solid phase, so that... 

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