Ordered mesoporous silica functionalized with ß-cyclodextrin derivative for optical isomer separation of flavanones and flavanone glycosides by nano-liquid chromatography and capillary electrochromatography

Abstract

In this paper a novel chiral stationary phase (CSP) was prepared by the immobilization of a ß-CD derivative (3,5-dimethylphenylcarbamoylated ß-CD) onto the surface of amino-functionalized spherical ordered mesoporous silica (denoted as SM) via a urea linkage using the Staudinger reaction. The CSP was packed into fused silica capillaries 100 ¿m I.D. and evaluated by means of nano-liquid chromatography (nano-LC) and capillary electrochromatography (CEC) using model compounds for the enantioseparation and the diastomeric separation. The compounds flavanone, 2¿-hydroxyflavanone, 4¿-hydroxyflavanone, 6-hydroxyflavanone, 4¿-methoxyflavanone, 7-methoxyflavanone, hesperetin, hesperidin, naringenin, and naringin were studied using reversed and polar organic elution modes. Baseline optical isomers resolution and good results in terms of peak efficiency and short analysis time of all studied flavonoids and flavanones glycosides was achieved in reversed phase mode, using a mixture of MeOH/H2O, 10 mM ammonium acetate pH 4.5 at different ratios as mobile phase. For the polar organic mode using 100 % of MeOH as mobile phase, the CSP showed better performances, the baseline chiral separation of several studied compounds occurred in an analysis time of less than 10 min. Also good results were achieved by CEC employing two different mobile phases. The use of MeOH/H2O, 5 mM ammonium acetate buffer pH 6 (90/10, v/v) was very effective for the chiral resolution of flavanone and its methoxy and hydroxy derivatives.