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. 2023 Nov 2;48(1):184-194.
doi: 10.55730/1300-0527.3650. eCollection 2024.

Voltammetric measurement of catechol-O-methyltransferase inhibitor tolcapone in the pharmaceutical form on the boron-doped diamond electrode

Musa Kiran  1 , Yavuz Yardim  2
Affiliations

Voltammetric measurement of catechol-O-methyltransferase inhibitor tolcapone in the pharmaceutical form on the boron-doped diamond electrode

Musa Kiran et al. Turk J Chem. .

Abstract

This study presents an electroanalytical approach to measure the catechol-O-methyltransferase (COMT) inhibitor tolcapone (TOL) using a boron-doped diamond (BDD) electrode. The application of cyclic voltammetry (CV) technique revealed that TOL exhibited a distinct, diffusion-controlled, irreversible anodic peak at a potential of approximately +0.71 V (vs. Ag/AgCl) in a 0.1 mol L-1 phosphate buffer solution (PBS) with a pH of 2.5. The oxidation of TOL is highly dependent on the pH and supporting electrolytes. Based on the data obtained from the pH investigation, a proposed mechanism for the electro-oxidation of TOL is suggested. Using the square wave voltammetry (SWV) technique, a satisfactory linear relationship was observed at approximately +0.66 V in a 0.1 mol L-1 PBS with a pH of 2.5. The presented method exhibited linearity within the concentration range between 1.0-50.0 μg mL-1 (3.7 × 10-6-1.8 × 10-4 mol L-1), with a limit of detection (LOD) of 0.29 μg mL-1 (1.1 × 10-6 mol L-1). The BDD electrode demonstrated good selectivity against inorganic ions and filler materials interference. Finally, the suitability of the developed approach was assessed by measuring TOL in tablet formulations, resulting in favorable recoveries ranging from 103.4% to 106.2%.

Keywords: Tolcapone; boron-doped diamond electrode; pharmaceutical form; voltammetric techniques.

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Figures

Figure 1
Figure 1
Repeated cyclic voltammograms (CVs) were obtained at a scan rate of 100 mV s−1 for 150 μg mL−1 TOL (A), CVs conducted at several scan rates (10, 25, 50, 100, 200, and 300 mV s−1) for 150 μg mL−1 TOL (B) in 0.1 M PBS at pH 2.5 on the BDD electrode. A: Dashed lines were used to represent the background current. B: Linear dependences of ip versus v 1/2 were displayed in the inset.
Figure 2
Figure 2
SW voltammograms were recorded for 50.0 μg mL−1 TOL in 0.1 M PBS at pH 2.5 on the BDD electrode after applying different electrochemical pretreatments. SWV parameters: ΔEs = 10 mV; ΔEsw = 40 mV; f = 50 Hz.
Figure 3
Figure 3
SEM images in different scale (10 μm and 0.2 μm) for the BDD electrode (A–B). SEM-EDX spectrum and elemental composition of the BDD electrode (C).
Figure 4
Figure 4
SW voltammograms for 50 μg mL−1 TOL in BR buffer (pH 2.0–7.0) (A) as well as various electrolytes at various pH ranges (B) at the CPT-BDD electrode. In Figure 2, the other working conditions are shown.
Figure 5
Figure 5
SW voltammograms with TOL concentrations of (1–9) 1.0, 2.5, 5.0, 7.5, 10.0, 20.0, 30.0, 40.0, and 50.0 μg mL−1 in 0.1 M PBS at pH 2.5 on the CPT-BDD electrode. The calibration graph for TOL measurement is presented inset. SWV parameters: ΔEs = 12 mV; ΔEsw = 60 mV; f = 100 Hz.
Figure 6
Figure 6
SW voltammograms of the drug sample; dashed line indicating the diluted drug sample, (1–5) after standard additions of 1.0, 2.5, 5.0, 10.0, and 20.0 μg mL−1 TOL. The inset displays the result of the analysis using the standard addition method. SWV parameters: ΔEs = 12 mV; ΔEsw = 60 mV; f = 100 Hz.
Scheme
Scheme
Possible mechanism of TOL oxidation.
See this image and copyright information in PMC

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Grants and funding

The authors would like to express their gratitude for the financial support provided by the Scientific Research Foundation of Van Yüzüncü Yıl University (project number: FDK-2021-9544).

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