276861 Liquid-Liquid Chromatography: Application of a Predictive Thermodynamic Model for the Selection of the Stationary and Mobile Phase
Liquid-liquid chromatography: Application of a predictive thermodynamic model for the selection of the stationary and the mobile phase
A. Frey, M. Minceva
Chair of Separation Science and Technology, Friedrich Alexander University
Liquid-liquid chromatography (LLC) is a unique separation technology, which combines the principles of extraction and chromatography. The separation is achieved as a result of different partitioning of the solutes between two liquid phases, while one of the phases is kept stationary by means of centrifugal forces. The limitless choice of solvents for the formation of biphasic liquid systems (the mobile and stationary phase) requires a systematic method for the selection of the appropriate solvent combination for a specific separation task. At the moment, this selection is performed by “trial and error” experimental screening procedures, using only a little number of solvents and solvent combinations.
A decisive parameter for the separation performance in LLC is the partition coefficient of the solutes present in the feed mixture. A good separation resolution, a reasonable separation time and not excessively diluted products can be obtained if the partition coefficient of the solute of interest is in the range from 0.4 to 2.5.
In this work a general approach for the selection of the mobile and the stationary phase for a specific LLC separation task is presented. The approach is strongly supported by the use of the a priori predictive thermodynamic method “Conductor-like Screening Model for Real Solvents” (COSMO-RS).
In the first step, potential solvents are selected based on criteria defined by the user. The solubility of the target solutes in the selected solvents is evaluated using the solvent capacity, calculated with COSMO-RS. After that, biphasic liquid systems (obtained by mixing of at least three solvents) are chosen from available liquid-liquid phase diagrams. In a next step, a screening of the pre-selected biphasic liquid systems is performed using the partition coefficient calculated with COSMO-RS.It is demonstrated that with the proposed approach the extensive experimental effort needed for the selection of the biphasic liquid system can be significantly reduced, if not completely eliminated.