Sol-gel molecular imprinted ormosil for solid-phase extraction of methylxanthines

A organically modified molecularly imprinted silica (MIS), selective for methylxanthines, was prepared using a simple sol-gel procedure. Caffeine was used as template; 3-aminopropyltrimethoxysilane (APTMS) as functional monomer and tetraethyl orthosilicate (TEOS) as reticulating agent. The material was packed on solid-phase extraction (SPE) cartridges and evaluated with aqueous test samples, natural water and human urine; a quantitative method for methylxanthines in water, using SPE cartridges packed with the MIS coupled with HPLC-UV was developed. The MIS was highly specific for methylxanthines, with an imprinting factor of (20.5 +/- 1.9). The analytical method resulted in detection limits of 85 mu g L-1 for theobromine, 44 mu g L-1 for theophylline and 53 mu g L-1 for caffeine. (c) 2006 Elsevier B.V. All rights reserved.