It is notorious that researches related to electrochemical sensors increased significantly due the promising characteristics that these devices present such as the possibility of obtaining information, with minimum manipulation of the studied system, in real time, and with low environmental impact. This article covers the carbon nanomaterials, presenting important aspects such as main properties, synthesis methods, and the application of these materials in the development of electrochemical sensors for the analysis of drugs and compounds of clinical interest. In this context, drug analysis is extremely important for quality control, to ensure that the medicine fulfills its role effectively without possible complications that could compromise the patient’s health and quality of life. In addition, analytical methods capable of determining compounds of clinical interest in biological fluids are extremely important for the indication of effective diagnoses. Thus, the versatility, selectivity, and portability of the electroanalytical techniques make the electrochemical sensors a favorite tool for the determination of drugs and compounds of clinical interest. It will be possible to follow in the present work that carbon nanomaterials have excellent thermal and electrical conductivity, strong adsorption capacity, high electrocatalytic effect, high biocompatibility, and high surface area. The possibility of formation of different composite materials based on carbonaceous nanomaterials that makes these materials promising for the development of analytical sensors, contributing to rapid, sensitive, and low-cost analyses can also be highlighted.

In this work, an electrochemical sensor based on pyrolytic graphite electrode (PGE), cobalt phthalocyanine (CoPc) and multiwalled carbon nanotube (MWCNT) composite designed as PGE‐MWCNT/CoPc was developed and validated for pyridoxine (vitamin B6) determination employing Differential Pulse Voltammetry (DPV). The electrochemical behaviour of pyridoxine at the PGE‐MWCNT/CoPc has been evaluated and the charge transfer coefficient, α, and the charge transfer rate constant, κ, were calculated as 0.30 and 11.67±0.43 s−1, respectively, which indicates that, although this system is irreversible, it is viable kinetically to be used as a sensor. The optimized experimental conditions were pH 5.5 in 0.30 mol L−1 phosphate buffer. The linear range found was 10 to 400 μmol L−1 of pyridoxine, with r=0.9987. The limits of detection and quantification were 0.50 and 1.67 μmol L−1, respectively, showing the good sensitivity of the method. The method was successfully applied for the pyridoxine determination in real samples of pharmaceutical formulation with RSD% lower than 5 % indicating that it can be used for routine quality control pharmaceutical formulations containing pyridoxine. Furthermore, it has the advantages of a fast response, a low detection limit and low cost.

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This work describes the development of a biosensor for paracetamol (PAR) determination based on a glassy carbon electrode (GCE) modified with multiwalled carbon nanotubes (MWCNT) and laccase enzyme (LAC), which was immobilized by means of covalent crosslinking using glutaraldehyde. Voltammetric investigations were carried out by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV). The biosensor was characterized by Scanning Electron Microscope (SEM) and Fourier Transform Infrared Spectroscopy (FT‐IR). The results showed that the use of MWCNT/LAC composite increased the sensor sensitivity, compared to bare glassy carbon electrode. Factors affecting the voltammetric signals such as pH, ionic strength, scan rate and interferents were assessed. Linear range, limit of detection (LOD) and limit of quantitation (LOQ) obtained were 10–320 μmol L−1, 7 μmol L−1 and 10 μmol L− 1, respectively. The developed biosensor was successfully applied to PAR determination in urine and pharmaceutical formulations samples, with recovery varying from 99.96 to 106.20 % in urine samples and a relative standard deviation less than 1.04 % for PAR determination in pharmaceutical formulations. Therefore, the MWCNT‐LAC/GCE exhibits excellent sensitivity and can be used to PAR determination as a viable alternative in clinical analyzes and quality control of pharmaceutical formulations, through a simple, fast and inexpensive methodology.

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