Application of a molecularly imprinted polymer based on the polyimide as a piezosensor selective coating for determining the oleic acid in oils

Abstract

When creating selective piezoelectric sensors based on the molecularly imprinted polymers (MIPs), the possibility of using quantum-chemical modeling for the selection of their synthesis conditions was considered. The starting polymer for MIPs production was polyamic acid (PAA), which is a copolymer of 1,2,4,5-benzenetetracarboxylic acid and 4,4′-diaminodiphenyl ether. Applying two-step thermal imidization of PAA solution in the presence of a template, the molecularly imprinted polyimide was formed. The oleic acid served as the template. The structures were optimized and the energies were calculated by the Gaussian 09 software using the DFT method at the B3LYP/6-31G(d,p) level with the basis set superposition error (BSSE) correction. It was shown that the structure of the fatty acid radical plays the decisive role in the formation of prints and, accordingly, in the selectivity of the polymer. Based on the quantum-chemical calculations, the optimal ratio of the reagents in pre-polymerization mixture was set to 4:1. The molecularly imprinted polymers for oleic acid have been synthesized on the surface of piezoelectric sensors by the non-covalent imprinting method. The ability of the obtained sensors to recognize this acid in the binary and ternary model mixtures of fatty acids was experimentally evaluated, and it was found that the sensor based on the molecularly imprinted polymer was most sensitive to the oleic acid, which had the detection limit of 0.14 g/dm 3 . Piezoelectric sensors based on MIPs were approved for the determination of the fatty acid in vegetable oils (sunflower, corn, olive, linseed, and rapeseed). The chromatography-mass spectrometry was used as the comparison method, and it was found that the difference in determination results was less than 10%. Keywords : molecularly imprinted polymers, polyamic acid, polyimide, oleic acid, computer modeling, modified piezosensors (Russian) DOI: http://dx.doi.org/10.15826/analitika.2019.23.1.006 Cao Nhat Linh, О.V. Duvanova, A.N. Zyablov Voronezh State University, Universitetskaya square, 1, Voronezh, 394018, Russian Federation