StatusThe thesis was presented on the 24 February, 2006
Approved by NCAA on the 27 April, 2006
Abstract– 0.27 Mb / in romanian
ThesisCZU 543.253 0.65 Mb / in romanian
Investigations of the electrochemical behavior of Cu(II), Pb(II), and Cd(II) ions in the presence of some thiosemicarbazides derivatives which differ by substitute, coordination ability, and rigidity of the molecules, shown important effects of adsorption of the organic reagents and their metal complexes on the mercury electrode. An original method for evaluation of the stability constant of the adsorpted species,has been proposed. It was demonstrated that the monosubstituted potassium phthalate in the system Сd(П) - 4-phenylthiosemicarbazide plays an important role not only for stabilization of pH, but it is also favorable to the formation and stabilization of the electroactive species. Introduction of the phenyl radical in the thiosemicarbazide molecule increases the sensitivity of the analytical signal, and makes possible the determination of the cadmium content up to the concentration 4*10(-9) M. Substitution of the sulfur atom by oxygen in the molecule of 8-quinolinaldehyde thiosemicarbazone changes the selectivity of the organic reagent. In the presence of 8-quinolinaldehyde semicarbazone it is possible the selective determination of the lead, reducing 2-3 times the mass of the samples. Using the adsorptive accumulation on the electrode, a number of original methods for determination of the heavy metal in different systems have been developed. The 4-phenylthiosemicarbazide has been proposed for determination of the cadmium in river waters, the thiosemicarbaziddiacetic acid and 8-quinolinaldehyde thiosemicarbazide – for copper determination in the river waters, apple and tomato juices, 8-quinolinaldehyde semicarbazone - for determination of the lead in wheat flour and petrol. The metrological parameters of the proposed methods have been evaluated using standard additions, AAS spectrometry, and reference materials.