Electroanalysis of a Ternary Disinfectant Mixture

Abstract

The analysis of a ternary mixture containing ozone (O₃), sodium hypochlorite (NaClO), and hydrogen peroxide (H₂O₂), in their coexistence was simultaneously performed using a potentiometric method. In this method, the change in the open circuit potential of a Pt indicator electrode dipped in a potential buffer containing I⁻/ upon the addition of the ternary mixture is measured. The analysis was based on the different reaction kinetics of the three oxidants with I⁻. The kinetics of the reaction of O₃ and I⁻ is about three orders of magnitude faster than that of sodium hypochlorite, and the reaction of hydrogen peroxide and I⁻ is negligible compared with those of O₃ or hypochlorite ion and I⁻ unless a molybdate catalyst is added. Several factors, including the iodide concentration, pH, and the molybdate concentration were investigated to optimize the analysis and achieve a reasonable separation among the reactions of the three oxidants and I⁻. A theoretical model was developed to compare with the experimental results and a reasonable correlation was obtained.

Keywords:

• Electroanalysis
• Hypochlorite
• Ozone
• Peroxide
• Potentiometry