Goates, SR
1991
Methanol/CO2 Phase Behavior in Supercritical Fluid Chromatography and Extraction
Page, S.H.; Goates, S.R. and Lee, M.L.
The Journal of Supercritical Fluids, 4:109-117, 1991. Funded by Gas Research Institute.
Mixed mobile phases have often been used improperly in supercritical fluid chromatography (SFC) and supercritical fluid extraction (SFE). Phase separation is unavoidable at certain conditions where conventional SFC and SFE are performed, resulting in inhomogeneous mobile phases. We describe here a relatively rapid and accurate approach to determining transition pressures at different temperatures and modifier concentrations. There is close agreement between the experimental values determined in this work and those published by others for methanol and carbon dioxide. The results have been used to test the predictions of several common methods for estimating the critical pressures of mixtures. The methods failed to predict the critical pressure to within 20 atm between approximately 4-20 mol % of modifier. Chromatographic performance was shown to be severely degraded when the pressure in the column is below the gas-liquid transition pressure. The effect of pressure drop in the column on phase behavior is discussed.
1990
Conditions and Effects of Mixed Mobile Phases on Capillary Column Chromatographic Performance in the Near Critical Region
Page, S.H.; Goates, S.R. and Lee, M.L.
Twelfth International Symposium on Capillary Chromatography, Kobe, Japan, 1990. Funded by Gas Research Institute.
The phase behaviors of binary compositions of carbon dioxide with organic modifiers (acetonitrile, methanol and propylene carbonate) were studied using laser light scattering in the near critical region (0-20 mol%, 80-400 atm, and 60-120ºC). In order to maintain supercritical fluid conditions, the pressure, temperature, and mole percent must be properly adjusted for each composition. The three regions of two-phase phenomena are described.
Goates, SR
1991
Methanol/CO2 Phase Behavior in Supercritical Fluid Chromatography and Extraction
Page, S.H.; Goates, S.R. and Lee, M.L.
The Journal of Supercritical Fluids, 4:109-117, 1991. Funded by Gas Research Institute.
Mixed mobile phases have often been used improperly in supercritical fluid chromatography (SFC) and supercritical fluid extraction (SFE). Phase separation is unavoidable at certain conditions where conventional SFC and SFE are performed, resulting in inhomogeneous mobile phases. We describe here a relatively rapid and accurate approach to determining transition pressures at different temperatures and modifier concentrations. There is close agreement between the experimental values determined in this work and those published by others for methanol and carbon dioxide. The results have been used to test the predictions of several common methods for estimating the critical pressures of mixtures. The methods failed to predict the critical pressure to within 20 atm between approximately 4-20 mol % of modifier. Chromatographic performance was shown to be severely degraded when the pressure in the column is below the gas-liquid transition pressure. The effect of pressure drop in the column on phase behavior is discussed.
1990
Conditions and Effects of Mixed Mobile Phases on Capillary Column Chromatographic Performance in the Near Critical Region
Page, S.H.; Goates, S.R. and Lee, M.L.
Twelfth International Symposium on Capillary Chromatography, Kobe, Japan, 1990. Funded by Gas Research Institute.
The phase behaviors of binary compositions of carbon dioxide with organic modifiers (acetonitrile, methanol and propylene carbonate) were studied using laser light scattering in the near critical region (0-20 mol%, 80-400 atm, and 60-120ºC). In order to maintain supercritical fluid conditions, the pressure, temperature, and mole percent must be properly adjusted for each composition. The three regions of two-phase phenomena are described.