Analytical capabilities of the electrochemical sensors based on the transition metal oxide nanomaterials

Development of the sensitive and selective electrochemical sensors is one of the main streams of modern analytical chemistry. Chemically modified electrodes are created for these purposes. Transition metal oxide nanomaterials (nanoparticles, nanorods, nanoflakes, nanoneedle, etc.) are of interest among the modifiers due to high stability, chemical and electrochemical inertness, high surface area and biocompartibility. Voltammetric sensors based on the CeO₂, SnO₂ and CeO₂·Fe₂O₃ nanoparticles, and MnO₂ nanorods have been developed for the quantification of various organic substances. Surfactant media have been applied as dispersive agents for metal oxide nanomaterials providing high stability of the dispersions after sonication, decrease of the nanoparticles size as well as preconcentration of the target analytes at the sensor surface due to the hydrophobic interactions between the surfactant and analyte molecules. Natural phenolics (quercetin, rutin, gallic acid, taxifolin, eugenol, vanillin, hesperidin), propyl gallate, α-lipoic acid and synthetic food colorants (tartrazine, brilliant blue FCF and sudan I) have been studied as analytes. The effect of the nature and concentration of surfactant on the target analyte response has been evaluated. Cationic surfactants (cetylpyridinium or cetyltriphenylphosphonium bromides) show the best effect for the majority of the analytes. The wide linear dynamic ranges and low detection limits have been obtained and are improved vs. reported to date. Simultaneous quantification of tartrazine and brilliant blue FCF has been achieved with high selectivity. The practical applicability of the sensors is shown on the real samples and is validated by comparison to independent methods.