The Use of Piezosensors for Determination of Carboxylic Acids in the Intermediate Products of Edible Ethanol Production

The reference polymers and polymers with molecular imprints of carboxylic acids (MIPs-CA)—propionic (MIP-Propionic) and butyric (MIP-Butyric) acids—were synthesized on the surface of piezoelectric sensors using aromatic compounds by the non-covalent imprinting method. A molecularly imprinted polymer (MIP) is a polymer produced through molecular imprinting, which leaves cavities in the polymer matrix with affinity for a chosen “template” target molecule. The values of the imprinting factor and selectivity coefficients were calculated to assess the ability of MIPs-CA to recognize the target molecules. It was shown that the sensors modified by the molecularly imprinted polymers exhibited high selectivity for the acid that was a template during their synthesis. The detection limits for propionic and butyric acids were 7.40 × 10–6 and 8.81 × 10–6 g/dm3, respectively. Correctness of the carboxylic acid determination in model solutions was verified in the spike/recovery tests. The relative standard deviation was less than 10%. The modified piezoelectric sensors were tested in analysis of the intermediate products of edible ethanol production (distillate of fermentation mixture, epurate, bottom liquids of columns). The correctness of the determination of carboxylic acids in liquids was evaluated using an Agilent Technologies 7890B GC System. The difference in the results of acid determination between both methods (piezoelectric sensor and chromatography–mass spectrometry) did not exceed 6%. The modified piezosensors expand the potential of rapid determination of carboxylic acids in the intermediate products of ethyl alcohol production.