Desenvolvimento, caracterização e aplicação de um sorvente monolítico polimérico para preparação rápida e portátil de amostras

Abstract

Sample preparation is the fundamental step in a chemical analysis to obtain a reproducible, accurate, and reliable result. The most conventional methods of sample preparation are liquid-liquid extraction and solid-phase extraction. However, these methods have some disadvantages leading to the search for alternative sample preparation methods that reduce the generation of toxic waste, are fully portable, miniaturized, and require microvolumes of organic solvents. One method that meets these requirements is disposable pipette extraction (DPX). However, this method has low commercial availability of sorbents (limited selectivity) and requires filters to retain the sorbent inside the tips. In this work, we proposed replacing the finely divided powder with a monolithic organic sorbent for organic compounds from aqueous samples. An organic polymeric monolith was synthesized by in situ polymerization of the trimethylolpropane triacrylate (TMPTA), methacrylic acid (MAA), and ethylene glycol dimethyl methacrylate (EDMA), using isopropanol as a porogenic and 2,2'-azobisisobutyronitrile (AIBN) as a radical initiator. The proportion of the monomers was optimized to obtain monoliths with a rigid structure, highly porous, and compatible with continuous flow extraction processes. The best condition reached was 70 % isopropanol, 5 % TMPTA, 5 % MAA, and 20 % EDMA. The poly(TMPTA-co-MAA-co-EDMA) monoliths were characterized morphologically and structurally and showed a solid structure composed of globule nuclei. The results of infrared spectroscopy and thermogravimetric analysis confirmed the complete polymerization. The produced monoliths were used to extract caffeine from water samples. The caffeine extraction from water samples was reached through the interaction of the monolith with the analyte. Caffeine sorption in the monoliths proved to be satisfactory and suitable for rapid and fully portable extraction, with the possibility of in-loco application of xanthine in aqueous samples with the poly(TMPTA-co-MAA-co-EDMA) monoliths in the micropipette tips.