Grafting of molecularly imprinted polymers from the surface of silica gel particles via reversible addition-fragmentation chain transfer polymerization: a selective sorbent for theophylline.

Molecularly imprinted polymers (MIPs) were grafted successfully from the surface of silica gel particles via surface initiated reversible addition-fragmentation chain transfer (RAFT) polymerization using RAFT agent functionalized silica gel as the chain transfer agent. The intrinsic characteristics of the controlled/living polymerization mechanism of RAFT allowed for the effective control of the grafting process. Thus the grafting copolymerization of methacrylic acid and divinyl benzene in the presence of template theophylline led to thin MIP film coating silica gel (MIP-Silica). The thickness of MIP film prepared in this study is about 1.98 nm, which was calculated from the nitrogen sorption analysis results. Measured binding kinetics for theophylline to the MIP-Silica and MIPs prepared by conventional bulk polymerization demonstrated that MIP-Silica had improved mass-transfer properties. In addition, the theophylline-imprinted MIP-Silica was used as the sorbent in solid-phase extraction to determine theophylline in blood serum with satisfactory recovery higher than 90%. Nonspecific adsorption of interfering compounds can be eliminated by a simple elution with acetonitrile, without sacrificing the selective binding of theophylline.