Partitioning of organics between ionic liquids and supercritical CO2: Limiting K-factors in [bmim][N(CN)2]-scCO2 system and generalized correlation with cation- and anion-specific LSERs

Infinite dilution partition coefficients (K-factors) of a selection of organic solutes in biphasic 1-n-butyl-3-methylimidazolium dicyanamide ([bmim][dca])-supercritical carbon dioxide (scCO(2)) system were obtained from retention measurements by open tubular capillary column supercritical fluid chromatography (SFC) with [bmim][dca] serving as the stationary liquid and scCO(2) as the carrier fluid. Therefore, the SFC-based route to solute K-factors in ionic liquid (IL)-scCO(2) systems is feasible even with low viscosity ILs such as [bmim][dca]. The experimental K-factors in [bmim][dca]-scCO(2) system were used to test an earlier generalized correlation of solute K-factors in IL-scCO(2) systems. Further, another version of the generalized correlation was introduced and tested. In the linear solvation energy (LSER) part of the former correlation the IL has been treated as a single species whereas, in the new version, the IL cation- and anion-specific LSER part has been employed. The introduction of the ion-specific LSERs resulted in some performance improvement of the correlation. (C) 2015 Elsevier B.V. All rights reserved.