Novel strategy for online monitoring of the degradation kinetics of propantheline bromide via a calixarene-based ion-selective electrode

•Novel use of ISEs for online monitoring of the degradation kinetics of hydrolysable drug.•Real-time observation for continuous profile of the hydrolysis behaviour of PB under various pH and temperature conditions.•Increased accuracy in rate constants estimation superior to the off-line chromatographic and spectrometric techniques.•The prepared sensor shows high selectivity, minimal potential drift and short response time.

Propantheline bromide (PB) is a hydrolysable anti-cholinergic drug. A novel strategy for the online monitoring of PB degradation kinetics catalysed by hydroxyl ions is presented. This is achieved by the incorporation of an on-site PB-selective electrode constructed using as an ionophore. This sensor was used to track the hydrolysis of PB by continuous measurement of the decrease in the produced emf over time. The use of this new technique provides real-time observation and yields a continuous profile of the hydrolysis behaviour of PB under various pH conditions as well as the temperature dependency of each reaction. Moreover, a great advantage of this proposed on-line system is its higher accuracy for rate constant estimation relative to other off-line methods. This kinetic data analysis permitted the determination of the hydrolysis activation energy and prediction of the drug shelf life. The estimated activation energy from Arrhenius plot was 20.77 kcal mol−1.

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