A novel method for determination of Cu(I) and Cu(II) the reaction of copper ions with dimethylindodicarbocyanine dye

Complete text of publication follows. Copper is an important bioelement that is present in animals, plants and microorganisms. It is both vital and toxic to many biological systems, depending on the level of concentration. In biosystems copper exists in two characteristic forms, with oxidation numbers of I and II and takes part in oxidation-reduction processes. One notable function of copper is its influence on the metabolism of iron. Another function is its direct influence on the activity of some enzymes. In this work, the reactions of various copper ions with 1,3,3-trimethyl-2-[5-(1,3,3-trimethyl- 1,3-dihydroindol-2-ylidene)-penta-1,3-dienyl]-3H-indolium - more commonly known as dimethylindodicarbocyanine polymethyne dye (DIDC) - as well as the application of the results obtained for the development of a spectrophotometric method for the determination of Cu(I), and Cu(II) are described. Cu(I) and Cu(II) in the presence of chloride ions and DIDC reagent are extractable by a variety of organic solvents. It is important to emphasize that Cu(I) was extracted under considerably different experimental conditions than Cu(II). The optimum conditions for the extraction of the Cu ion associates with DIDC by amyl acetate and the determination of Cu(I) and Cu(II) were found to be: pH 3-5 and pH 3-6 and chloride concentrations of 0.5-0.8 mol L-1 and 3-6 mol L-1 for Cu(I) and Cu(II), respectively. The molar absorptivities for Cu(I) and Cu(II) are 1.8 x 105 L mol-1 cm-1 and 1.2 x 105 L mol-1 cm-1, respectively. A reaction mechanism is also suggested. Acknowledgements. This work has been supported by the Scientific Grant Agency of the Ministry of Education of the Slovak Republic and the Slovak Academy of Sciences (Grant No. 1/4451/07) and internal grant systems of Faculty of Science of Pavol Jozef Safarik University in Kosice (VVGS Grant No. 24/2009/CH).