Enhanced selectivity of a molecularly imprinted polymer toward the target molecule via esterification of non-specific binding sites with diazomethane

Diazomethane (CH2N2) was used to methylate the non-specific binding sites after molecularly imprinted polymer particles were prepared using methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linker and bisphenol A (BPA) as the template. After diazomethane treatment and subsequent removal of BPA by triethylamine, the treated molecularly imprinted polymer (TMIP) particles were tested for binding selectivity toward BPA and other organic compounds by capillary electrophoresis with ultraviolet detection. Even in the presence of compounds that were positively charged, neutral or negatively charged in the background electrolyte, BPA was selectively bound with the highest efficiency. A significant decrease in the affinity for metformin (MF, a positively charged compound), along with C-13 nuclear magnetic resonance spectra and electrophoretic mobility data, provided strong evidence for the elimination of non-specific -COOH binding sites in the TMIP particles. Only 8% of MF and 16% of diclofenac sodium salt (a negatively charged compound) remained as non-specific bindings because of hydrophobic interactions. Further comparison with poly(methyl methacrylate) revealed the true merits of the TMIP, which exhibited minimal non-specific bindings while preserving a high level of specific binding owing to molecular recognition. Copyright (c) 2014 John Wiley & Sons, Ltd.