Selective separation of aspirin using molecularly imprinted polymers

The molecular imprinting technique (MIT) is a potential method for creating molecular recognition sites with high selectivity to the target molecule in polymeric materials. The goal of this study was the selective separation of aspirin (AS) having various effects as pharmaceutics using the molecularly imprinted polymers (MIPs). The MIPs were prepared with styrene, 4-vinylpyridine (4-VPy) as a functional monomer, templates (AS, salicylic acid (SA), and 1,2,3,4-tetrahydro-1-naphthol (THN)), and divinylbenzene (DVB) as a cross-linker. The template extraction for each MIP was performed by the Soxhlet extraction and swelling process. The binding characteristics of MIPs and templates (AS, SA, and THN) were evaluated using equilibrium binding experiments. Scatchard plot analysis revealed that two classes of binding sites were formed with the equilibrium dissociation constants. Also, the adsorption ability of the MIPs was evaluated by high performance liquid chromatography (HPLC) analysis, measuring the adsorbed amounts for a similar imprinted template structure, the selectivity factor (α), and the imprinting-induced promotion of binding (IPB). SA, which could not be separated using SA-imprinted polymer because of its intramolecular hydrogen bonding, was separated using THN-imprinted polymer, which was prepared using THN having similar structure on the intermolecular hydrogen bonded SA. The effects of pH and temperature on the selective separation were confirmed because AS is hydrolyzed to SA and acetic acid with changes in pH and temperature. The MIPs synthesized in this study showed excellent adsorption properties in the pH and temperature ranges investigated. The present study results can be expected to have a profound effect on the prevention or diagnosis of disease by their application in the control of optimum dose of AS based on individual constitutions.