An Investigation of the Interaction between Resazurin and Cd²⁺ and Zn²⁺ Ions in Aqueous Medium

Abstract

The voltammetric behaviour of resazurin in the presence of Cd²⁺ and Zn²⁺ ions at a hanging mercury drop electrode (HMDE) was investigated by using square wave voltammetry (SWV), cyclic voltammetry (CV) and adsorptive square wave voltammetry (AdsSWV). The interaction of resazurin with Cd²⁺ and Zn²⁺ starts above pH 4 and seems to be completed at pH 5.2 with Cd²⁺ ions and at pH 7.5 with Zn²⁺ ions. A new peak appears at –0.93 V in the presence of Cd²⁺ and at –1.07 V in the presence of Zn²⁺. These peaks may be attributed to M²⁺–resazurin complexes and the logarithm of their stability constant was determined where log β_1:1 = 4.22 for Cd2+-resazurin and log β_1:1 = 4.74 for Zn²⁺-resazurin. Cyclic voltammetry was used to characterize the redox mechanism and to calculate voltammetric data of M²⁺-resazurin complexes. The amount of adsorbed M²⁺-resazurin complexes on the mercury drop electrode surface (Γ) is calculated as 5.48 × 10^–12 mol cm^–2 for Cd²⁺-resazurin and 1.10 × 10^–11 mol cm^–2 for Zn²⁺-resazurin. The voltammetric data were compared with the data obtained using spectrophotometric methods and were observed to be in good agreement.

Keywords: Resazurin, Cadmium, Zinc, Electrochemistry, Spectroscopy, Metal Complexes