Voltammetric Determination of Hydroxychloroquine Used in the Treatment of COVID‐19 at MWCNT Modified Pencil Graphite Electrode

COVID-19, the most significant pandemic of the 21st century, has prompted the use of various drugs to slow down the viral process in patients infected with it. One of these drugs is hydroxychloroquine, and due to its importance and frequent use in the treatment of COVID-19, its rapid, accurate and inexpensive determination in biological or pharmaceutical samples is very important. In this study, the electrochemical behavior of hydroxychloroquine was investigated, and voltammetric determination of hydroxychloroquine was performed with a pencil graphite electrode modified with multi-walled carbon nanotubes. Scanning electron microscopy images were used to examine the surfaces of both the regular pencil graphite electrode and the modified one with multi-walled carbon nanotube. Cyclic voltammetric measurements showed that hydroxychloroquine was irreversibly oxidized at approximately +700 and +900 mV in Britton Robinson buffer solution at pH 10.0. Considering these oxidation peaks, differential pulse voltammetric determination of hydroxychloroquine was carried out under optimized conditions. A linear response was obtained from the multi-walled carbon nanotube-modified pencil graphite electrode in the range of 0.1 to 200 µmolL-1 for peaks at both +700 mV and +900 mV with detection limits of 0.04 and 0.05 µmolL-1, respectively. The method was tested on the real tablet and water samples; nearly 100 % recovery was achieved for hydroxychloroquine spiked into the water sample, while the amount of the labeled compound in the pharmaceutical tablet was accurately determined. This result confirmed that the multi-walled carbon nanotube-modified pencil graphite electrode is very effective for selectively and accurately determining hydroxychloroquine in real samples.