Preparation and evaluation of calix[4]arene-capped β-cyclodextrin-bonded silica particles as chiral stationary phase for high-performance liquid chromatography

Calix[4]arene-capped [3-(2-O-β-cyclodextrin)-2-hydroxypropoxy]propylsilyl-appended silica particles (C4CD-HPS), a new type of substituted β-cyclodextrin-bonded chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC), have been synthesized by treatment of bromoacetate-substituted [3-(2-O-β-cyclodextrin)-2-hydroxypropoxy]propylsilyl-appended silica particles (BACD-HPS) with calix[4]arene oxyanions in anhydrous N-methyl-2-pyrrolidone. The synthetic stationary phase is characterized by means of elemental analysis. This new type of CSP has a chiral selector with two recognition sites: calix[4]arene and β-cyclodextrin (β-CD). The chromatographic behavior of C4CD-HPS was studied with several disubstituted benzenes and some chiral drug compounds under reversed-phase conditions. The results show that C4CD-HPS has excellent selectivity for the separation of aromatic positional isomers and enantiomers of chiral compounds due to the cooperative functioning of calix[4]arenes and β-CDs.