Preparation and evaluation of a deoxycholic-calix[4]arene hybrid-type receptor as a chiral stationary phase for HPLC.

We report the synthesis and enantioseparation characteristics of two novel covalently immobilized deoxycholic acid derivatives as chiral stationary phases for high-performance liquid chromatography. In the structure of the first stationary phase, the 3-position of deoxycholic acid is substituted with a 3,5-dinitrophenylcarbamoyl group and the second one has an additional calix[4]arene attached to the carboxylic group of the deoxycholic acid. The chromatographic performance of the stationary phases was evaluated with enantioseparation of N-(3,5-dinitrobenzoyl)-dl-leucine, N-(3,5-dinitrobenzoyl)-dl-valine, omeprazole, diclofop-methyl, dl-mandelic acid and (RS)-pregabalin. Comparison of the performance characteristics of the prepared chiral stationary phases provided evidence for the active involvement of the calix[4]arene unit in the chiral recognition process. Both stationary phases are chemically bonded to the silica and can be used in both normal-phase and reversed-phase modes.

Characterization of a dicationic imidazolium-based ionic liquid as a gas chromatography stationary phase.

Here we report the characteristics of a new synthesized ionic liquid, 1,9-di(N-naphthalen-2-ylimidazolium)nonane bis[(trifluoromethyl)sulfonyl]imide ([C9(2NPTim)2][(NTf2)2]), as a stationary phase by inverse gas chromatography. The McReynolds constants demonstrated that the [C9(2NPTim)2][(NTf2)2] had an average polarity of 667 and polarity number P.N.=75, suggesting its polar nature. The solvation properties of the new stationary phase were determined by the calculation of Abraham solvation system constants, whereby the results showed that its major interactions with the analytes included H-bond basicity (a), dipole-dipole (s) and dispersive (l) interactions. The activity coefficients (γ∞) and selectivities (SIJ∞) at infinite dilution were also determined for various polar and nonpolar organic solutes at different temperatures. The separation performance of the [C9(2NPTim)2][(NTf2)2] stationary phase was evaluated by GC separations of different analytes, including normal alkanes and aromatic compounds. The TGA results showed that the stationary phase had high thermal stability up to 420°C.