Selective and simultaneous extraction and determination of hydroxybenzoic acids in aqueous solution by magnetic molecularly imprinted polymers

Two novel magnetic molecularly imprinted polymers (MMIPs) based on benzonic acid (BA)14-hydroxybenzoic acid (4-HBA) as template have been successfully developed to selectively and simultaneously extract and determine five hydroxybenzoic acids [BA, 4-HBA, salicylic acid (SA), protocatechuic acid (PCA), and gallic acid (GA)] in aqueous solution. Various parameters affecting adsorption/desorption behavior are evaluated for achieving optimal recovery. Under optimum conditions, adsorption process between MA/4-HBA and MMIPs follows Langumuir adsorption isotherm and pseudo-second-order reaction kinetics. Thermodynamic parameters reveal that adsorption process is spontaneous, endothermic and entropy driven one. Both MMIPs show high adsorption capacity, good selectivity, rapid kinetic binding (40 min) and magnetic separation (10 s), favorable reproducibility (RSD <4% for batch-to-batch evaluation), and stability (only 6% decrease after six cycles). The adsorption capacities of 4-HBA, PCA and GA on 4-HBA-MMIPs are higher because of higher molecular analog degree to template, whereas BA and SA with higher capacities on BA-MMIPs are observed. Spiked recoveries of five hydroxybenzoic acids on BA-MMIPs and 4-HBA-MMIPs range from 83.2% to 103.0% with RSD less than 6.9%. Results demonstrate that both resulting MMIPs could be reliably applied to direct extraction and determination of hydroxybenzoic acids from real aqueous solution. (C) 2014 Elsevier B.V. All rights reserved.