Flow injection analysis of acetic acid in food samples by using trienzyme/poly(dimethylsiloxane)-bilayer membrane-based electrode as the detector

The concentration of acetic acid was determined by a combination of flow injection analysis (FIA) with amperometric trienzyme sensor detection. The enzyme sensor was prepared by immobilizing acetate kinase (AK), pyruvate kinase (PK) and pyruvate oxidase (PyOx) on a poly(dimethylsiloxane) (PDMS)-coated electrode. AK catalyzes the phosphor-transferring reaction between acetic acid and ATP to form ADP; PK, the phosphor-transferring reaction between ADP and phosphoenolpyruvate (PEP) to form pyruvic acid; and PyOx, the oxidation of pyruvic acid with oxygen. The oxygen consumption was monitored by using the PDMS-coated electrode without the interference from the PyOx reaction product, hydrogen peroxide. Thus the sensor-based system could be used for the determination of acetic acid from 0.05 to 20 mM with the sampling rate of 20 h−1, and was stable for a month. The FIA system could successively be applied to wines.