Analytical methods for selectively determining hydrogen peroxide, peroxymonosulfate and peroxydisulfate in their binary mixtures

Hydrogen peroxide (H2O2), peroxymonosulfate (PMS), and peroxydisulfate (PDS) are key bulk oxidants in many advanced oxidation processes (AOPs) for treating chemically contaminated water. In some systems these peroxides may coexist in solution either through intentional co-addition or their inadvertent formation (especially H2O2) due to reaction chemistry. While many analytical methods to determine these peroxides individually have been established, mutual interference among the peroxides in such methods has seldom been evaluated, and new methods or variants of established methods to selectively determine peroxides in binary mixtures are lacking. We re-examined five established colorimetric methods-the Permanganate, Titanium Oxalate (Ti-oxalate), Iodide, N.N‑diethyl-p-phenylenediamine (DPD), and 2,20-azino-bis(3-ethylbenzothiazoline-6-sulfonate (ABTS) methods-for mutual interference among peroxides and devised variants of these methods for selectively quantifying one peroxide in the presence of another. Hydrogen peroxide can be selectively determined by the Permanganate method at short reaction time; by the Ti-oxalate method; by the DPD method with added peroxidase (POD); or by the ABTS method with added POD. PMS can be selectively determined by the Iodide method; by the DPD or ABTS methods with added iodide ion as catalyst; or by the DPD method with added catalase (CAT) (with co-existing H2O2 but not PDS). The DPD method can be used to determine PDS without interference by H2O2 and-provided the sample is pretreated with l-histidine-without interference by PMS. The recommended methods were successfully applied to binary peroxide mixtures in complex waters, including a tap water and a synthetic water. Overall, the new selective methods will assist mechanistic investigation of AOPs based on these peroxides and support efforts to apply them commercially.