Potentiometric and 1H NMR Spectroscopic Studies of Functional Monomer Influence on Histamine-Imprinted Polymer-Modified Potentiometric Sensor Performance

For the development of a histamine (HIS) potentiometric sensor based on molecularly imprinted polymers (MIPs), the effects of four functional monomers, namely acrylamide (AA), atropic acid (AT), methacrylic acid (MAA), and 4-vinylpyridine (4-VP), from which the MIP was synthesized, on the performance of the HIS sensor were examined by potentiometric and 1H nuclear magnetic resonance (NMR) spectroscopic methods. The intermolecular interactions between HIS as a template molecule and a functional monomer were investigated based on the 1H NMR spectra of HIS in distilled water in the presence of each functional monomer. Changes to the chemical shift of each HIS proton indicated that HIS typically formed a HIS-functional monomer complex at a ratio of 1:1 via hydrogen bonding with AA, AT and MAA, and interacted with 4-VP between the imidazole ring and pyridine ring of 4-VP. The potential changes of the four HIS sensors were measured in 0.1×10-3 mol L-1 aqueous solution using Ag/ AgCl as a reference electrode; the order of the magnitudes of the changes was MAA>AA=4-VP>AT. The potential changes of three non-imprinted polymer-modified potentiometric sensors prepared without HIS were smaller than those of the corresponding HIS sensors, except in the case of AT. The potential response and selectivity of the HIS sensor using MAA were better than those of the other three HIS sensors. The 1H NMR spectroscopic and potentiometric results showed that the hydrogen bond between HIS and MAA strongly and effectively influenced the potential response of the HIS sensor.