Electrochemical Kinetics and Detection of Paracetamol by Stevensite-Modified Carbon Paste Electrode in Biological Fluids and Pharmaceutical Formulations.

Paracetamol (PCT), or acetaminophen, is an important drug used worldwide for various clinical purposes. However, the excessive or indiscriminate use of PCT can provoke liver and kidney dysfunction; hence, it is essential to determine the amount of this target in biological samples. In this work, we develop a quick, simple, and sensitive voltammetric method using chemically modified electrodes to determine PCT in complex matrices, including human serum and commercial solid formulations. We modify the carbon paste electrode with stevensite monoclinic clay mineral (Stv-CPE), using cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy to characterise and detect PCT. The kinetics study provides a better electrochemical characterisation of the electrode behaviour, finding the detection and quantitation limits of 0.2 µM and 0.5 µM under favourable conditions. Further, the best linear working concentration range is 0.6-100 µM for PCT, applying the proposed method to the quantitative determination of PCT content in reference tablet formulations and biological samples for validation.

A Carbon Paste Electrode Modified by Bentonite and l-Cysteine for Simultaneous Determination of Ascorbic and Uric Acids: Application in Biological Fluids.

A novel modification of a paste carbon electrode by Bentonite (Bent) and l-Cysteine (l-Cyst) was carried out for uric acid (UA) and ascorbic acid (AA) detection and quantification. Morphological and compositional characterization of the electrode surface were carried out using electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopic analysis (EDS). Cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques were used to analyze UA and AA. The obtained sensor shows a good stability, sensibility, selectivity, and regeneration ability. Accordingly, the limit of detection (LOD) is found to be 0.031 µm and 9.6 µm for UA and AA, respectively. A good linearity in the range of 0.1 to 100 µm for UA and 10 to 1000 µm for AA was obtained. The peak-to-peak separation of UA-AA (ΔEUA-AA ) was determined to be 330 mV. In addition, the sensor is applied successfully to monitor UA and AA in serum samples.