Sílica organicamente modificada e molecularmente impressa foi preparada através de um procedimento sol-gel simples, e avaliada como sorvente específico para extração em fase sólida (Solid Phase Extraction, SPE) de fenobarbital em amostras aquosas e forenses. As propriedades analíticas dessa sílica molecularmente impressa (MIS, molecularly imprinted silica) foram inicialmente avaliadas e o material determinado como específico para as espécies-alvo: o fator de impressão IF, medido como a razão entre o pico do fenobarbital em cromatogramas de MIS e NIS (sílica não-impressa) foi estimado como 58. Este valor é consideravelmente maior que aquele apresentado normalmente para sorventes de impressão convencional baseados em metacrilatos e sugere que interações não-específicas analito/sorvente são insignificantes no MIS. O material foi aplicado no isolamento de fenobarbital de amostras aquosas e plasma; limites de detecção de 10 e 62 µg mL -1 , respectivamente, foram encontrados para essas amostras.A molecularly imprinted organically modified silica was prepared through a simple sol-gel procedure, and evaluated as specific sorbent for solid-phase extraction (SPE) of phenobarbital from aqueous and forensic samples. The analytical properties of the molecularly imprinted silica (MIS, non-imprinted sílica) were initially evaluated and the MIS was found to be specific towards the target species: the imprinting factor IF, measured as the ratio between phenobarbital peak areas in the MIS and NIS chromatograms, was estimated as 58. This value is considerably higher than those usually found for conventional methacrylate-based molecularly imprinted sorbents and suggests that non-specific analyte/sorbent interactions are insignificant in the MIS. This material is applied to the isolation of phenobarbital from aqueous samples and plasma; detection limit of 10 and 62 µg mL -1 was achieved for the former samples, respectively. Keywords: molecularly imprinted silica, sol-gel, ormosils, phenobarbital, SPE IntroductionThere is a demand for sensitive, accurate and simple analytical procedures. One of the tools to achieve these goals is the incorporation of biomolecules and biologicallike processes in the methodologies. However, despite of the specificity achieved on these procedures, natural biomolecules usually are expensive and chemically unstable. Synthetic materials such as molecularly imprinted polymers (MIP) are valid alternatives to these biological matrices. Molecular imprinting was proposed by Pauling 1 as a possible mechanism for the production of antibodies by living systems. According to his model, the synthesis of antibodies was based on the use of the aggressor chemical molecules as templates. Weak intermolecular forces such as hydrogen bonding or van der Waals forces drove proper monomer units to organize themselves around the antigen. Polymerization of the organized monomers and removal of the template would render macromolecules with cavities where the template or other species with similar structure could be highly select...

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