Capacity ratios and diffusion coefficients of low-volatile organic compounds in supercritical carbon dioxide from supercritical fluid chromatography (SFC) |
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Authors: | A Wilsch R Feist GM Schneider |
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Institution: | Department of Chemistry, University of Bochum, 4630 Bochum, Federal Republic of Germany |
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Abstract: | Capacity ratios k have been determined for phenyl myristate, phenyl palmitate and phenyl stearate from supercritical fluid chromatography (SFC) at 35 to 56°C and 85 to 190 bar using supercritical CO2 as mobile phase and Perisorb A and Perisorb RP8 as stationary phases. For the esters used a rise in pressure from 90 to 190 bar produces a drop of k by about two orders of magnitude giving evidence of the rapidly increasing solvent power of supercritical CO2 with increasing density. At a constant CO2 density, k decreases with increasing temperature. The separation of the esters was found to be the better the lower the pressure was. An apparatus for the chromatographic determination of binary diffusion coefficients in supercritical gases is described. D12 values for some organic compounds in carbon dioxide at 40°C and in the pressure range from 80 to 160 bar are presented. With an improved electronic flow regulator an overall precision of the D12 values of ±3% is obtained. |
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