Electrochemical sensors in electroanalysis are a particularly useful and relatively simple way to identify electroactive substances. Among the materials used to design sensors, there is a growing interest in different types of carbon. This is mainly due to its non-toxic properties, low cost, good electrical conductivity, wide potential range, and the possibility of using it in both aqueous and nonaqueous media. The electrodes made of carbon, and especially of carbon modified with different materials, are currently most often used in the voltammetric analysis of various compounds, including preservatives. The objective of this paper is to present the characteristics and suitability of different carbon materials for the construction of working electrodes used in the voltammetric analysis. Various carbon materials were considered and briefly discussed. Their analytical application was presented on the example of the preservatives commonly used in food, cosmetic, and pharmaceutical preparations. It was shown that for the electroanalysis of preservatives, mainly carbon electrodes modified with various modifiers are used. These modifications ensure appropriate selectivity, high sensitivity, low limits of detection and quantification, as well as a wide linearity range of voltammetric methods of their identification and determination.

The first voltammetric method of identification and determination of phenoxyethanol (PE) in pharmaceutical and cosmetic preparations has been successfully developed. The measurements were carried out using differential pulse voltammetry (DPV) on a platinum microelectrode in glacial acetic acid containing acetonitrile (20%, v/v) and 0.1 mol L⁻¹ sodium perchlorate as supporting electrolyte. A linear voltammetric response for PE was obtained in wide concentration range from 5.4 × 10⁻⁶ to 1.5 × 10⁻³ mol L⁻¹, with low detection limit of 3.6 × 10⁻⁷ mol L⁻¹. The repeatability and reproducibility of the peak current for phenoxyethanol concentration of 3.6 × 10⁻⁵ mol L⁻¹ expressed as % RSD (n = 10) were very good and do not exceeded 0.5% and 0.8%, respectively. The obtained results indicate that the developed method allows sensitive, accurate and precise determination of PE in pharmaceuticals and cosmetics without the need for its separation from the matrices. The proposed method is simple and fast so it can serve as an analytical alternative for chromatographic techniques.

Thymol and carvacrol—the components of herbal spices—are known for their broad biological activity as antimicrobials and antioxidants. For this reason, it is important to develop new methods for their determination in plant material. A simple, rapid, and sensitive method for determination of total content of these analytes in herbal spices using differential pulse voltammetry (DPV) has been developed. The basis of the research is the oxidation process of isopropylmethylphenols on a platinum microelectrode in glacial acetic acid containing acetonitrile (20%, v/v) and 0.1 mol L⁻¹ sodium perchlorate as the supporting electrolyte. Linear voltammetric responses for thymol and carvacrol were obtained in a wide concentration range from 0.39–1105 and 0.47–640 µg mL⁻¹, with a low detection limit of 0.04 and 0.05 µg mL⁻¹, respectively. The analysis was performed using the multiple standard addition method. The results of the voltammetric determination are in good agreement with the data of the standard chromatographic method. To the best of our knowledge, this is the first presentation of an electrochemical procedure to determine these compounds in these environmental and electrode materials.

A simple, highly sensitive, and selective differential pulse voltammetry method for the determination of α-lipoic acid (LA) in pharmaceutical preparations was developed and validated. The method is based on a quasi-reversible, diffusion-controlled, one-electron anodic oxidation of LA on a boron-doped diamond electrode (BDDE) in a McIlvaine (citrate-phosphate, C-PB) buffer solution at pH 3.0. For the first time, this environment was used for LA determination. A linear calibration curve was obtained within the concentration range 5.82 × 10 −8 to 4.00 × 10 −4 mol L −1 with a correlation coefficient of 0.9999. The limits of detection was estimated to be 1.94 × 10 −8 mol L −1 , which is one of the lowest values characteristic of voltammetric and chromatographic methods of LA determination. The proposed procedure is sensitive, accurate, and precise. Its utility was demonstrated in the determination of LA in pharmaceuticals without the need for its separation from the matrices. The results were comparable to those obtained by high performance liquid chromatography reference method and were in good accordance with the once declared by manufacturers. Thus, our method can be considered as an alternative to the dominant chromatographic determinations of α-LA in real samples.