Indicator carbon-paste electrode for voltammetric analysis
A procedure for manufacturing an indicator carbon-paste electrode of ergonomic design and testing of the electrode for voltammetric determination of a number of substances of inorganic and organic origin aredescribed. This electrode is made of a high purity graphite rod (Æ6 mm, L = 70 mm) coated with insulation and having a cavity filled with electroactive carbon-containing material at the end of the rod. The characteristic features of the proposed electrode - the insulating body shell made of heat-shrink tube and electrolytic coating of the cavity surface with a conductive metal film - can simplify the design of the electrode and improve the mechanical strength, extend the life of the electrode, and provide the possibility of volumetric and surface modifications with sparing application of the modifying reagents. The performance and metrological characteristics of the new indicator carbon paste electrode were evaluated in testing food, beverages, natural objects for heavy metal ions and pharmaceuticals for hydrogen peroxide and riboflavin (vitamin B<sub>2</sub>) using various options: cyclic voltammetry with a linear sweep, square pulse, differential pulse, and inverse voltammetry. When using the developed electrode modified with a bismuth film for determination of cadmium and lead ions, the linear dynamic range of the calibration characteristic was 10 - 110 and 10 - 160 μg/dm<sup>3</sup>, respectively. The linear dynamic range of the calibration characteristic for riboflavin determination was 0.01 - 0.2 mmol/liter (3.76 - 75.3 mg/liter) for electrode volume-modified with the microparticles of manganese dioxide. The same electrode, modified with MnO<sub>2</sub> nanoparticles obtained during reduction of Mn (VII) ions by Mn (II) ions in a neutral medium was used in chrono-amperometric determination of hydrogen peroxide in model and pharmaceutical preparations with a detection limit 0.03 mmol/liter for H<sub>2</sub>O<sub>2</sub>. The simplicity of manufacturing the developed indicator carbon-paste electrode, high performance, and cost-effectiveness when using expensive and scarce modifiers, allows us to recommend it to be used in voltammetric analysis and design of various biosensor systems.