Thermo-responsive molecularly imprinted monolith in extraction

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Molecularly imprinted polymers (MIPs) are widely employed sorbents due to their improved selectivity. They are synthesized in the presence of the analyte, which is called template, and therefore the polymeric network is constructed around the target leaving selective chemical cavities when it is washed away. After the bulk synthesis, the polymer is crashed and sieved to obtain a solid with a particle size as homogeneous as possible. In a recent article published in Analytical and Bioanalytical Chemistry, researchers from the Tianjin Medical University at China have proposed a smart MIP monolith for the extraction of ketoprofen from milk samples.

In an old post entitled “Smart molecularly imprinted hydrogels for protein recognition”, we discussed the advantages of these materials that combine the selectivity enhancement of MIPs with the advantages of smart polymers. In short, a smart polymer is a porous polymeric network that may respond to external stimulus (mainly pH, ionic strength or temperature) with a change in its structure or dimension. This change can be used to control the uptake and release of the analytes with a negligible effect on the polymeric network that memorizes the imprinting state.

In the new article, the authors synthesized a monolith avoiding the crashing and sieving process and therefore improving the reproducibility of the material. A monolith is a one-block polymer comprising large pores (macropores) that favor the sample flow through the polymer and small pores (mesopores) that increase the superficial area of the network. The main challenge that the authors found in their development was the selection of the porogenic solvent. In fact, the low solubility of the thermo-responsive monomer in conventional solvents made necessary the use of dimethylsulfoxide (DMSO) as solvent although it provides the polymeric network with a low porosity. This shortcoming was avoided using an ionic liquid as modifier in the synthesis. The IL increases the porosity and permeability of the resulting polymer.

The smart-MIP showed selective molecular recognition towards the target analyte when it was compared with the non-imprinted polymer (NIP), synthesized in the absence of template. This selectivity was thermo-dependent; at temperatures lower than 35 ºC the MIP performance was superior to that showed by the NIP while at higher temperatures both polymers presented a more uniform behavior.

We recommend this article to our readers. The article describes the synthesis of the polymer, the optimization of that process, the characterization of the material and its final application for the extraction of ketoprofen from milk samples.

References
(1) Thermoresponsive ketoprofen-imprinted monolith prepared in ionic liquid. Link to the article

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