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Square wave voltammetric pKa determination of aspirin using multi-way data analysis models

Zehra Yazan, Dilek Eskiköy Bayraktepe, and Erdal Dinç

Department of Chemistry, Faculty of Science, Ankara University, Tandoğan, Turkey



Received: 6 February 2022  Accepted: 19 April 2022


To understand the drug action mechanism, the acid–base dissociation constant (or pKa) of biologically active compounds is one of the most functional parameters of physicochemical properties. In this respect, it is vital to develop new methodologies for the pKa determination of active substances. In our case, the acid dissociation constant (or pKa value) of aspirin was quantified by applying parallel factor analysis (PARAFAC) and multivariate curve resolution alternating least squares (MCR-ALS) to the square wave voltammetric measurements. In preliminary experiments, to generate second-order data matrix, which can be provided a change in the current with pH and frequency variation, the pH range and frequency range with steps were tested and identified as pH 1–pH 6 (increasement 1) and 10–100 Hz (increasement 10), respectively. Voltammetric datasets were obtained as a function of potential (mV) and frequency (Hz) in water at six different pH levels using the BR buffer solutions. The acidity constants were obtained as 3.39 and 3.35 from pH profiles of the acid–base species of aspirin in dissociation equilibrium. This work revealed that PARAFAC and MCR-ALS models of the voltammetric datasets would be a good alternative to the traditional methods for estimating acid ionization constant.

Graphical abstract

Keywords: Parallel factor analysis; Multivariate curve resolution alternating least squares; Acid ionization constant; Aspirin

Full paper is available at

DOI: 10.1007/s11696-022-02250-9


Chemical Papers 76 (9) 5389–5397 (2022)

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