This study re-evaluated the DPD/POD (N,N-diethyl-p-phenylenediamine/peroxidase from horseradish) spectrophotometric method for accurately detecting low-concentration hydrogen peroxide in water. It established that the absorption coefficient of the adduct product, DPD•+, at a wavelength of 320 nm was approximately two times higher than at 551 nm, indicating lower detection limits at 320 nm for H2O2 measurement. An optimal POD/DPD ratio of 1 was identified for effective H2O2 concentration determination. The effect of selected anions (chloride, sulfate, nitrate, and carbonate) on H2O2 determination was found to be negligible at concentrations below 1 g L–1; however, at higher concentrations, these anions exhibited varying impacts on H2O2 measurement. The enhanced DPD/POD method is demonstrated as an effective tool for investigating the mechanism of vacuum ultraviolet (VUV) processes by accurately detecting low-concentration H2O2 formed in situ during the photolysis of water. The findings provide insights into the optimal conditions for H2O2 determination by this spectrophotometric method and highlight the minimal influence of inorganic anions under specific conditions. This study not only enhances the understanding of H2O2 measurement in VUV-induced reactions but also underscores the potential applications of the DPD/POD method in exploring the dynamics of VUV processes.

KEY WORDS: Spectrophotometric method, Hydrogen peroxide, Peroxidase from horseradish, Vacuum ultraviolet.

Bull. Chem. Soc. Ethiop. 2025, 39(3), 397-408.                                                      

DOI: https://dx.doi.org/10.4314/bcse.v39i3.1