Preparation and characterization of 4-isopropylcalix[4]arene-capped (3-(2-O-β-cyclodextrin)-2-hydroxypropoxy)-propylsilyl-appended silica particles as chiral stationary phase for high-performance liquid chromatography.

A new type of 4-isopropylcalix[4]arene-capped (3-(2-O-β-cyclodextrin)-2-hydroxypropoxy)propylsilyl-appended silica particles (IPC4CD-HPS) has been prepared by treatment of bromoacetate-substituted (3-(2-O-β-cyclodextrin)-2-hydroxypropoxy)propylsilyl-appended silica particles (BACD-HPS) with 4-isopropylcalix[4]arene oxyanions in anhydrous N-methyl-2-pyrrolidone. The bonded silica IPC4CD-HPS has been successfully used as chiral stationary phase (CSP) in high-performance liquid chromatography (HPLC) for the first time. The synthetic stationary phase was characterized by means of elemental analysis and Fourier transform infrared spectroscopy. This new CSP has a chiral selector with two anchored functional moieties: 4-isopropylcalix[4]arene and β-cyclodextrin. The chromatographic performance of IPC4CD-HPS was investigated by separation of positional isomers of several disubstituted benzenes and enantiomers of some chiral drug compounds under reversed-phase conditions. The results showed that IPC4CD-HPS had excellent selectivity for the separation of aromatic positional isomers and enantiomers of chiral compounds due to the cooperative functioning of the anchored 4-isopropylcalix[4]arenes and β-cyclodextrins.