New HPLC stationary phases based on (methacryloyloxypropyl-β-cyclodextrin-co-N-vinylpyrrolidone) copolymers coated on silica. Preparation and characterisation

Abstract

New silica based supports for use in HPLC separations have been prepared by the coating of a series of copolymers containing various molar fractions of vinylpyrrolidone (VP) and methacryloyloxypropyl beta cyclodextrin (βW7 MAHP) units on LiChrospher Si100. These chromatographic supports were fully characterised using the following techniques: thermogravimetric analysis, specific area and porous volume measurements, scanning electron micrography, NMR, EDAX and RAMAN spectroscopy. It was demonstrated that the interactions of the copolymer with the silica surface imply the VP units through H-bonding between the amide groups and the silanol functions explaining the increase of the polymer adsorption with the VP residue content. The analysis of the surface area, porous volume and pore size distribution showed that the coating process involved first the largest pores of silica and in a second step the smallest ones. From the ²⁹Si NMR spectroscopy and scanning electron microscopy analysis, it appears that only the supports with high amounts of polymer adsorbed ensured a complete passivation of the silanol groups.