Partition coefficients of phenol, salicylic acid, and several environmentally important chloro- and nitrophenols in a supercritical CO2-water system were measured using direct cocurrent extraction of aqueous solutions of the individual solutes with CO2. Partitioning data on the nitrophenols and salicylic acid were obtained for the first time. To bypass the troublesome and error-prone analysis of the CO2-rich phase, the present method employed only the solute concentrations in the aqueous phase before and after extraction to determine the partition coefficient. Unlike most previous engineering studies of phenol partitioning in a CO2-water system, the concentrations of phenolic solutes approached infinite dilution in both phases. This makes the results relevant to analytical-scale SFE of environmental water samples with CO2. Because of effective infinite dilution of the solutes, the partition coefficients provide a direct measure of relative CO2-philicity/hydrophilicity of the individual phenols. Compared to the octanol-water partition coefficients of substituted phenols, the CO2-water partition coefficients are more sensitive to substitution in the position neighboring the hydroxyl group.
Development of packed capillary columns using carbon dioxide slurriesA modified procedure for the preparation of packed capillary columns by the use of supercritical or liquid carbon dioxide slurries is proposed. This technique removes the problems arising from sudden and rapid movement of sorbent suspension at the beginning of the filling process. The parameters influencing the packing process (temperature, pressure, and restrictor that controls the flow rate of CO 2 ), have been optimized. The columns prepared under optimized conditions exhibit high efficiency (average value of the reduced plate height h 9 ca. 2.2), and long term stability. An example of the SFC separation of polydimethylsiloxanes in silicone oil is presented.
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