The design of an indicator carbon-paste electrode of ergonomic design and testing of an electrode for voltammetric determination of a number of substances of inorganic and organic origin is described. The electrode is made of a graphite rod with a diameter of 6 mm and a length of 70 mm, covered with insulation and having a cavity filled with an electroactive carbon-containing material at the end of the rod. The characteristic features of the proposed electrode - the insulating shell of the housing made of shrink tubing and the electrolytic coating of the cavity surface with a conductive metal film - make it possible to simplify the design of the electrode and increase mechanical strength, extend the service life of the electrode, and also provide the possibility of volumetric and surface modifications with economical consumption of modifying reagents.
The working and metrological characteristics of the new carbon-paste indicator electrode were evaluated when testing food products, beverages, natural objects for the content of heavy metal ions and pharmaceuticals for the content of hydrogen peroxide and riboflavin (vitamin B2), ascorbic acid (vitamin C) using various options: cyclic and inversion voltammetry with linear sweep, rectangular and differential pulses.
When using the developed electrode modified with a bismuth film to determine cadmium and lead ions, the linear dynamic range of the calibration characteristic was 10-110 and 10-160 micrograms/dm3, respectively. The linear dynamic range of the calibration characteristic for the determination of riboflavin was 0.01 - 0.2 mmol/L (3.76 - 75.3 mg/L) for a volumetrically modified nano/microparticles of manganese dioxide electrode. The same electrode, modified with MnO2 nanoparticles obtained by reducing Mn(VII) ions with Mn(II) ions in a neutral medium, was used for chronoamperometric determination of hydrogen peroxide in model and pharmaceutical preparations with a detection limit of 0.03 mmol/L for H2O2.
The simplicity of manufacturing the developed carbon-paste indicator electrode, high performance and cost-effectiveness when using expensive and scarce modifiers allow us to recommend it for use in voltammetric analysis and the creation of various biosensor systems.
