An electroanalytical method for monitoring acid hydrolysis reactions using thick-film modified electrodes

•-Thick-film modified electrodes are used to study the transfer of ionisable drugs.•-The half-wave potential of the electrochemical process can be predicted from models.•-The half-wave potential reveals information about degradation kinetics.•-We can determine pseudo-first order kinetic constants from mid-peak potentials. Many organic compounds of pharmaceutical interest undergo unwanted reactions that reduce their effectivity or even generate harmful products. One of the many possible mechanisms for these degradation reactions is acid hydrolysis. We propose the use of the thick-film modified electrode setup to follow the acid hydrolysis reaction of water-soluble compounds that contain protonatable sites. We focus on the determination of the first order or pseudo-first order kinetic constant in the aqueous phase. The developed procedure is presented using a model for the transfer of protonated species at liquid|liquid interfaces coupled with an electron transfer process at the solid|liquid interface. Moreover, we experimentally validate this strategy by determining the kinetic constant for the degradation of tylosin A in acidic solutions. [Display omitted]