Novel restricted access chiral stationary phase synthesized via atom transfer radical polymerization for the analysis of chiral drugs in biological matrices.

A new restricted access chiral stationary phase was designed and synthesized via atom transfer radical polymerization (ATRP). Surface modified bi-functional silica with chiral selector in the inner layer and hydrophilic external layer was prepared by taking advantage of the controlled/living property of the ATRP method. ATRP initiator bound porous silica was synthesized to perform surface initiated polymerization. The chiral stationary phase was then synthesized by grafting poly(glycidyl methacrylate) (pGMA) on the surface of the silica through "grafting from" polymerization followed by beta-cyclodextrin (beta-CD) immobilization. On the surface of this beta-CD immobilized material, the external pGMA layer was synthesized via second round ATRP using the initiator on the material. The hydrophilic structure was formed after the hydrolysis, which created a diffusion barrier for proteins. The new chiral restricted access material (chiral-CD-RAM) was characterized and its abilities for chiral separation and protein exclusion were evaluated. The result demonstrates that enantio-separations can be achieved for several drugs in HPLC using chiral-CD-RAM as stationary phase. Meanwhile, good protein recovery has been obtained. It indicated that this chiral-CD-RAM can be used for determination of certain chiral drugs in biological samples with direct injection in the HPLC analysis.