SummaryAsolventventingtechniqueforinjection ofvolumesuptol plon 50 pm i.d. SFC columns has been compared to direct injection methods.The peak broadening and peak splitting observed with direct injection have been examined and found to be related to the starting pressure, the column temperature, and the sample solvent, in addition to the sample volume. The solvent venting technique removed peak splitting and improved the column efficiency. With a proper selection of experimental conditions, the sample recoverywas 1 OO%.The major part of the solvent was eluted in 15-20 s. Several applications have been demonstrated.
SummarySupercritical carbon dioxide can be utilized both as an introduction solvent in capillary SFC and as a reaction medium; both possibilities are illustrated in this study. An off-line SFE unit was modified for on-line SFE-SFC. To facilitate rapid depressurization of the extraction cell and to prevent memory effects, a 6-port valve was installed at the outlet line of the extraction unit. An increased background signal was obtained when PEEK polymer was used in the construction of the extraction vessel; when stainless steel was used, the blanks improved. The synthesis of methyl esters and butyl esters of fatty acids from triglycerides in edible fat was examined using an immobilized lipase as a catalyst in on-line SFE-SFC. As a result of 30 minutes reaction -extraction time, high yields of fatty acid esters were obtained at a pressure of 150 bar and a temperature of 50°C.
Abstract. The solvent venting injection technique has been tested for 1-pL injections of lipids in open tubular column SFC. No sample loss during solvent venting was experienced with a 7-m precolumn at elevated temperatures. The solvent venting technique has also been combined with gas purging to concentrate the sample on-line with SFC. Injections totalling 10-50 pL of sample have been performed. The solvent venting technique with minor modifications in the instrumentation was utilized for group separations of triglycerides. Different techniques for solute focusing were tested. The best peak shape was obtained by a combination of phase ratio and low temperature focusing.
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