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Significance
Paracetamol (PCT) is a non-steroidal anti-inflammatory drug used to treat fever, pain, and inflammation. However, PCT overdose is dangerous and often leads to severe liver damage and, in extreme cases, liver failure. Additionally, environmental traces of PCT from medical waste highlight the need for precise analytical methods for its detection and quantification. Traditional analytical techniques such as liquid chromatography and mass spectrometry, although accurate, are often limited by high operational costs and complex sample preparation. On the other hand, electrochemical techniques using chemically modified electrodes offer a cost-effective analytical alternative with benefits in simplicity, speed, and sensitivity. Among these, carbon paste electrodes (CPE), modified with various materials have been studied for their efficient electrochemical properties. To this end, a new study was published in the International Journal of Molecular Sciences, conducted by Dr. Moaad Gharous, Dr. Loubna Bounab, Dr. Mohamed Choukairi from the Abdelmalek Essaadi University alongside Dr. Fernando J. Pereira, Dr. Roberto López and Dr. A. Javier Aller from the University of León in Spain, where the researchers developed a new electrochemical method for detecting PCT using a modified CPE incorporated with stevensite clay (Stv-CPE).
The team prepared the new Stv-CPE electrode by mixing graphite powder with stevensite clay and a binding agent (mineral oil) to form a homogeneous paste. This mixture was then packed into a plastic electrode casing with a copper wire to establish an electrical connection. The authors used Fourier-Transform infrared spectroscopy (FT-IR) to identify the functional groups present in the stevensite clay and confirmed that it is predominantly composed of silica with traces of magnesium, aluminum, iron, and calcium oxides. They also used scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) to provide detailed structural images of the clay’s morphology and elemental composition, demonstrating their small particle size and confirming the elemental makeup of the clay. Indeed, the FT-IR spectroscopy and SEM/EDS analyses confirmed the clay’s composition and morphology, which are critical parameters for electrochemical application. The small particle size (~50 nm) and high porosity enhance its suitability as a modifier due to improved surface area and electron transfer capabilities.
Moreover, the authors used cyclic voltammetry to assess the electrochemical behavior of the electrode in different buffer solutions and under varying conditions to optimize the electrode’s response to PCT. Furthermore, advanced techniques such as differential pulse voltammetry and electrochemical impedance spectroscopy were employed to refine further the understanding of the electrochemical properties of the modified electrode, including its sensitivity and stability.
The researchers systematically tested different compositions of the carbon paste to determine the optimal amount of stevensite clay that would provide the best electrochemical response. They evaluated the performance of the electrode under different experimental conditions, such as pH levels and buffer compositions, to establish the most favorable conditions for detecting PCT. They validated the electrode’s efficiency by testing it against standard solutions of PCT and spiked serum samples, ensuring the method’s reliability and accuracy. Tests were conducted in the presence of common interfering substances such as dopamine and tyrosine to assess further the selectivity of the electrode. In these studies, the authors found that the optimal clay content in the electrode was determined to be 15%, which provided the best balance between sensitivity and stability of the electrochemical response. They also demonstrated that the modified electrode has a low detection limit of 0.2 µM and a quantitation limit of 0.5 µM for PCT, making it highly suitable for detecting low concentrations of PCT in complex biological and pharmaceutical samples. Moreover, the electrode showed a robust linear response for PCT concentrations ranging from 0.5 µM to 100 µM, suitable for various analytical needs. This high degree of sensitivity and specificity is crucial for accurate diagnostics and environmental monitoring, ensuring that even minute quantities of contaminants can be detected and quantified effectively.
From a theoretical electrochemical point of view, even though the electrode processes show a complex kinetic behaviour, a thorough evaluation of the developed electrode kinetics was possible by the study of the CV waves, which allowed us to derive valuable information, very helpful for a better understanding of the redox cathodic and anodic processes. Thus, according to the kinetic calculations, this electrochemical system shows a predominant diffusion process as the most predominant mass transfer mechanism with good electronic transport properties and some degree of irreversibility in the electrode processes. The good electrochemical activity concerning the PCT redox reaction relates to the favourable π–π and π-n interactions between the PCT molecules and the π system of the Stv material. Thus, the planar PCT molecule has a structurally extensive conjugated system with improved reactivity compared to usual. Further, the conjugation process in the PCT molecule significantly reduces the basicity of the hydroxyl oxygen and amide nitrogen. Consequently, the amide group acts more as a hydrogen bond donor, whereas the carbonyl group acts as a hydrogen bond acceptor. However, the hydroxyl group can act as a donor and acceptor, which facilitates the formation of intra- and inter-molecular hydrogen bridges, particularly with the OH groups in Stv.
Furthermore, given the widespread use of PCT and its subsequent presence in environmental waters, there is a growing need to monitor pharmaceutical pollutants effectively. The study provides a tool for environmental scientists to detect and quantify pharmaceutical residues in water bodies, aiding in the assessment of pollution levels and the effectiveness of water treatment processes. This methodology is essential for maintaining ecological balance and ensuring the health of aquatic life. It is worth mentioning that the new method was successfully applied to quantify PCT in human serum samples and commercial tablet formulations, demonstrating its efficacy in complex matrices without significant interference from other components. Clinically, the ability to rapidly measure PCT levels in human serum can be vital in cases of suspected overdose or in managing therapeutic dosing. This developed method can potentially be integrated into clinical settings to provide quick feedback on drug levels, enhancing patient safety and treatment efficacy. In pharmaceutical manufacturing, this technique can be employed for quality control, ensuring that products meet specified standards without the need for more elaborate testing procedures. Additionally, the electrochemical approach developed in this study could be adapted to detect other drugs and biochemical agents, broadening its utility beyond just PCT. This adaptability makes it a versatile tool in the development of detection technologies for a wide range of substances, potentially leading to innovations in both environmental science and medical diagnostics.
Overall, the developed Stv-CPE-based electrode exhibited excellent selectivity when tested against potential interfering substances. Furthermore, the electrode showed good reproducibility and stability, indicating its potential for repeated use in routine analytical applications. These findings suggest that the developed voltammetric method by Abdelmalek Essaadi University and University of León researchers using a stevensite clay-modified carbon paste electrode is a practical, reliable, and economical option for the quantification of PCT in various environmental and clinical settings. Future studies could explore the method’s application to other pharmaceutical compounds and potential improvements in electrode design for enhanced sensitivity and selectivity.
Reference
Gharous M, Bounab L, Pereira FJ, Choukairi M, López R, Aller AJ. Electrochemical Kinetics and Detection of Paracetamol by Stevensite-Modified Carbon Paste Electrode in Biological Fluids and Pharmaceutical Formulations. Int J Mol Sci. 2023 ;24(14):11269. doi: 10.3390/ijms241411269.