Rapid and Facile Spectrophotometric Method for the Selective Determination of Peroxymonosulfate, Peroxydisulfate, and Hydrogen Peroxide in Ternary Mixtures

Abstract Peroxides such as peroxydisulfate (PDS), peroxymonosulfate (PMS), and hydrogen peroxide (H2O2) are important bulk oxidants used in wastewater treatment, bleaching, or leaching. In many of these processes and during electrosynthesis, they often coexist in complex mixtures. Selective quantification of each peroxide constitutes a fundamental step toward understanding and optimizing these processes. However, achieving selectivity poses a major analytical challenge since most quantification methods rely on the oxidative properties toward indicators and interference through coexisting peroxides is common. In this study, the different iodide oxidation kinetics of PDS, PMS, and H2O2 were utilized to differentiate between them. Time-resolved spectrophotometry at 350 nm under optimized assay conditions was established as a prerequisite for achieving sufficient selectivity and reliable quantification. The assay sensitivities reach 7.62 × 103 M–1 (PMS), 7.68 × 103 M–1 (H2O2), and 4.1 × 103 M–1 (PDS) while the limit of quantification is 6.6 μM (PMS), 3.9 μM (H2O2), and 17 μM (PDS). The degree of interference caused by coexisting peroxides was thoroughly investigated, and the proposed quantification procedure was successfully applied to real electrolysis samples. The simplicity and reliability of the developed method enables high-throughput screening of electrodes, electrolytes, or reaction conditions and allows quality control of processes.