Application of a copper-selective electrode coated wire type to the determination of copper(II) by potentiometric titrations with ethylenediamine in aqueous and nonaqueous solutions

Abstract

In this work, potentiometric titrations of the solution of the Cu(II) ione have been executed with ethylenediamine as complexing agent and the copper selective electrode coated wire type/SCE indicator system in aqueous and nonaqueous solvents. Because of the difficult conditions of the forma­tion of the Cu (II) ethylenediamine complex, due to the presence of parallel reactions influencing the position of the basic balance of the formation of the complex, this study discusses and deduces the equations for the calculation of the constant of the formation of the complex as well as the equations for the calculation of the free ethylenediamine. In all the cases a pronounced extreme of the curve of titration has been remarked in the final phase of the titration, whatever diluent was used. Similar results have been obtained using solvents such as: water, alcohol (methanol, ethanol, buthanol), which was expected having in mind the chemical resemblance of these compounds (polar mollecules), while a sharper extreme was obtained in N,N-dymethylformamide, which was expected as well because of the similar basic characteristics with ethylenediamine. The results obtained by this study show the exceptional advantage of ethylenediamine as complexing agent and also the possibility of the application of the copper selective electrode coated wire type/SCE indicating system for the determina­tion of Cu(II) in aqueous and non-aqueous solvents and for the determination of the constants of the determination of the formation of the ethylenediamine complex. .

Formiranje kompleksa Cu(II) sa etilendiaminom otežano je postojanjem paralelnih ravnoteža sa reaktantima, koji reagujući sa ligandom, etilendiaminom, ili Cu(II) jonom utiču na položaj osnovne ravnoteže građenja kompleksa. Polazeći od konstatacije da svojstva etilendiaminada gradi stabilne komplekse sa mnogobrojnim jonima u analitičkoj hemiji nisu dovoljno iskorišćena, u ovome radu izvršena je analiza mogućih efekata na položaj ravnoteže građenja kompleksa kao i izvođenje jednačina za ukupnu konstantu obrazovanja B2 i za izračunavanje koncentracije slobodnog etilendiamina. U radu su izvršena potenciometrijska ispitivanja rastvora Cu(II) jona sa etilendiaminom kao kompleksirajućim agensom uz bakar-selektivna elektroda/zasićena kalomelova elektroda (ZKE) indikatorski sistem u vodenim i nevodenim rastvorima. Dobijeni rezultati pokazali su izuzetnu vrednost etilendiamina kao kompleksirajućeg agensa u poređenju sa drugim, konvencionalnim kompleksirajućima agensima, a takođe i mogućnost primene bakar-selektivna elektroda/ZKE indikatorskog sistema za određivanje konstante obrazovanja Cu(en)22+ kompleksa. .