Investigation of voltammetric and spectroscophic behaviour of resazurin both in the presence and absence of metal ions

In this study, voltammetric and spectroscopic behaviour of resazurin in the absence and presence of some metals was investigated by voltammetric and spectroscopic techniques. The voltammetric behaviour of resazurin was studied on a HMDE in Britton-Robinson (B-R) buffers (pH 2.0-10.0) by using Square-Wave Voltammetry (SWV), Square-Wave Adsorptive Stripping Voltammetry (SWAdSV) and Cyclic Voltammetry (CV) techniques. The electrochemical response of resazurin is generally pH dependent. The voltammograms of resazurin exhibited a reversible and an irreversible peaks at pH<4. A new irreversible peak obtained in addition to these peaks at pH>4. It is observed that the currents and the potentials of all the peaks were dependent of pH. In this study the reversible peak observed (1U) can be inferred from the reduction of resorufin to dihydroresorufin and irreversible peak observed (2U) is inferred to catalytical hydrogen wave at pH<4. The new irreversible cathodic peak (3U), which was only seen at pH range 4 ? 10 at more positive potential can be attributed to reduction of protonated N-oxide to form of resazurin, The electrochemical parameters (Ip/Ep, Ip/v, Ip/v1/2, Ip/pH, Ep/pH Ip/tacc, ?, n, D, ?) of the compounds were determined. From the voltammeric data, electrochemical reduction mechanisms have been suggested for all peaks. However the calibration of resazurin was studied and the limit of quantification has been found as 1,08x10-7 mol/L and 6,06x10-9 mol/L for SWV and SWAdSV, respectively. The metal complexes of resazurin which formation with Zn(II), Se(IV) and Cd(II) ions in aqua solution were investigated by using voltammetric techniques and from the voltammetric data, the stociometry and constants of stability of these complexes were determined. The results which were obtained by voltammetric methods supported also with spectroscopic studies. On the UV-Vis spectrums of resazurin which was obtained in different pH levels, we observed the presence of resorufin (reduction form of resazurin losing the oxygen atom of N-oxide group) and protonoted resazurin forms depending on the pH of the solutions. On the other hand, , complexes stociometry and constants of stability of resazurin with Zn(II), Se(IV) and Cd(II) ions were calculated and then the results were compared and supported with voltammetric results.