A SPE Method with Two MIPs in Two Steps for Improving the Selectivity of MIPs.

Molecular imprinted polymers (MIPs) have been widely applied in the separation of compounds in complex matrixes due to the high selectivity for molecular recognition. However, MIPs not only adsorb the targeted molecule but also adsorb structurally similar analogues, which leads to some loss of selectivity. In this work, for improvement of selectivity of MIPs, a novel solid-phase extraction method with two MIPs in two steps (TMIPs-TSPE) was established. As a demonstration, two MIPs were prepared by using quercetin as the template and 4-vinylypyridine (4VP) and acrylamide (AM) as representative functional monomers, respectively. The adsorption properties and kinetic characteristics of the two MIPs showed that they had a distinct adsorption capacity and adsorption mechanism, which is the basis for establishment of TMIPs-TSPE. The TMIPs-TSPE method first used one of the two MIPs as adsorbent to extract molecules from a solution mixture containing quercetin and three analogues. Then the other MIP was used to achieve a second extraction of the extracted molecules from the first step. The results showed that the unique targeted molecule quercetin was extracted, which illustrates that TMIPs-TSPE improved the specificity of the MIPs. The process of molecular recognition can be influenced by the intensity of binding sites between MIPs and molecules. Moreover, it may also depend on the spatial orientation of molecules entering the cavities of MIPs, which deserves more attention as one important property for the development of molecular imprinting. These results demonstrated that the novel TMIPs-TSPE method contributes to the improved selectivity of MIPs.