Thematic area "Nanocomposites and nanomaterials"

N,S-Heterocyclic Azoreagents as a modifying agents for improvement of carbon electrodes properties
Smyk N.I., Zaporozhets O.A., Zabolotnyi E.V., Tumanik N.O.
Chemical Department, Taras Schevchenko National University of Kyiv, Lva Tolstogo street, 12, Kyiv-01033, Ukraine. 
E-mail: nataliiasmyk@knu.ua

Heavy metals (HM), Ag and Cu for instance, have wide industrial application. This leads to the possibility for exposure to aquatic and terrestrial organisms. The toxicity of HM ranges through several orders of magnitude depends on the HM forms. Therefore, their ionic form has been shown to be toxic to a variety of aquatic organisms, the others complexing forms are significantly less toxic, the long-term effects of nanoparticles are poorly understood. With due to attention to this instances, silver(I) and copper(II) speciation determination is very important.
The one of the most sensitive methods for determining of HM “free” ions is stripping voltammetry (VA). Historically mercury electrodes have been widely used in SVA, but due to its toxicity, they are avoided now. However, the carbon paste electrode (CPE) and glass carbon electrode (GCE) attracted considerable attention in recent years. CPE and GCE have several advantages such as non-toxic, low back-ground current, wide range of used potential, rapid renewal or easy fabrication. The main disadvantage is the poor selectivity. Modification of electrodes with organic reagent lets to improve not only a sencitivity, but a selectivity of the electrochemical measurements by preconcentrating the target analyte from dilute solution on the electrode surface. 
N,S-azoreagents (R) such as Pyridylazoresorcinol, Thiazolylazonaphthol (TAN) and Dithizone (H2Dz) that are formed a stabilе complexes with  Cu2+ and Ag+ were selected as modifying agents in the represented work. The properties of modified electrodes were studied using potentiometry and cyclic VA. The GCE surface modified and CPE bulk modified with R were used as VA sensor for speciation of Cu2+ and Ag+. The best results were obtained for GCE coated with film containing H2Dz and CPE modified with TAN adsorbed onto SG surface for Ag+ and Cu2+.respectively. Under the optimal experimental conditions, the stripping current was proportional to Ag+ concentration over the range 0,1 – 25 µM and to Cu2+ concentration range 0,05 – 20 µM. The high sensitivity, stability and selectivity, including to the other coexisting forms of HM, of this electrodes demonstrated practical utility for simple, rapid and low-cost determination of Ag(I) and Cu(II) ions in water samples, bodily fluids and medicines.