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

Peroxides such as peroxydisulfate (PDS), peroxymonosulfate (PMS) and hydrogen peroxide (H 2 O 2 ) 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 towards understanding and optimizing these processes. However, achieving selectivity poses a major analytical challenge since most quantification methods rely on the oxidative properties towards indicators and interference through coexisting peroxides is common. In this study, the different iodide oxidation kinetics of PDS, PMS, and H 2 O 2 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. Employing low iodide concentrations and short reaction times, enable selective PMS quantification. By adding molybdate catalyst, the determination of H 2 O 2 is realized. Finally, the PDS concentration is derived from the total peroxide content obtained under optimized assay conditions by subtracting the H 2 O 2 and PMS concentration. The assay sensitivities reach 7.62 × 10 3 M −1 (PMS), 7.68 × 10 3 M −1 (H 2 O 2 ) and 4.1 × 10 3 M −1 (PDS) while the limit of quantification is as low as 6.6 µM (PMS), 3.9 µM (H 2 O 2 ) and 17 µM (PDS). The degree of interference caused by coexisting peroxides was thorougly 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.