Apparatus for supercritical fluid chromatography with carbon dioxide as the mobile phase

Abstract

For example, the A-15 resin, although qualitative, requires more energy for swelling than for the D-50 resin. Consequently, the A-15 resin must possess a more rigid resin matrix or must swell to a greater degree compared to the D-50 resin. It appears that both contribute to the net result. Since the D-50 resin collapses upon drying and must solvate before becoming solvent permeable, while the A-1 5 resin can be used in solvents which provide poor swelling properties, it is necessary to assume that the A-15 resin is more rigid and resistant to contraction (or swelling). Bead swelling for the A-15, although smaller than the D-50, also plays a significant role even though the resin is a porous type resin.The difference in rate of heat evolution for the two types of resins is consistent with their porous and gel character. Solvent must penetrate the dried, shrunken D-50 bead, and included in the overall process is a swelling rate. The A-15, although shrunken, is still porous enough so that a more rapid rate is observed initially.Similarly, for the different M-form resins the more viscous n-propanol (in comparison to methanol) is able to penetrate the A-15 resin. For the D-50 resin in n-propanol the rate of heat evolution is so slow that precise A& measurements are not possible within the time permitted for the measurement. An apparatus designed for supercritical fluid chromatography for operation at ambient temperatures and pressures up to 5000 psi is described. This particular unit has been especially developed for operation with C 0 2 as the mobile phase. An improved version of an earlier described mercury displacement pump ( 1 )is used to drive the mobile phase. High pressure nitrogen is still the primary pressure source, but pistons having spring-loaded Teflon seals are used instead of mercury as the pressure transfer medium. By incorporating the pressure intensification principle in the unit, high output pressures can be attained with a regular 2000-psi nitrogen source. To prevent problems associated with the decompression of the supercritical phase to a gas, we have constructed a high pressure ultraviolet detector cell which has been successfully used up to 4300 psia. A high pressure fraction collector system is used to collect the eluant from the chromatographic system. The analysis of alkylbromides and of some metal organic compounds is given as examples of the separations which can be obtained with this unit.

Homogeneous Catalysis in Supercritical Fluids

“…There is certainly a need for solubility data for inorganic compounds in other SCFs. Transition metal complexes known to dissolve in scCO 2 , but for which quantitative data are unavailable include phosphine complexes, 60 porphyrin complexes, 74,75 metallocenes, [76][77][78] carbonyls, 79 and metal oxinates. 80 Polar complexes, charged complexes, and even nonpolar complexes with many aryl-substituted ligands often have insufficient solubility to be used as catalysts.…”

“…73 Addition of CO 2 -philic "ponytails" such as polyfluoroalkyl, fluoro ether, or silicone groups, often as substituents on aryl rings can increase the solubility of metal complexes. 77,[81][82][83] The longer the fluorinated alkyl chain, the better the solubility. 84 Often, the first two carbons in the ponytail are unfluorinated, so that the electronwithdrawing effect of the group is mitigated.…”

Supercritical carbon dioxide injection in supersonic beam mass spectrometry

“…Supercritical fluids or dense gases are a class of solvents that are generating considerable interest and applications in analytical chemistry, as both chromatographic (9)(10)(11)(12) and spectroscopic solvents (13)(14)(15). Recent studies using supercritical fluids as solvents for thermooptical measurements have shown a more than 100-fold sensitivity improvement, relative to thermal lens and photothermal deflection measurements in carbon tetrachloride (14,15).…”

Pressure control of a liquid chromatograph pump

“…The only pressure programming in SFC to our knowledge has been by Jentoft and Gouw (2,11,12) and Nieman and Rogers (5) but specifications for pump performance were not mentioned. Using a pneumatic amplifier pump, Nieman and Rogers could achieve reproducibility of desired pressure to approximately 5%, with pulses causing difficulties at low pressures.…”