Spectrophotometric determination of trace hydrogen peroxide via the oxidative coloration of DPD using a Fenton system

A low-cost and environmentally-friendly spectrophotometric method for hydrogen peroxide (H 2 O 2 ) determination based on the oxidative coloration reaction of N,N′ -diethyl- p -phenylenediamine (DPD) via the Fenton reactions in aqueous water was established. The generated pink radical cation (DPD + ) showed maximum absorption at 551 nm. Importantly, under the optimal conditions (pH 3.0, 20 mM DPD, 1.5 mM Fe(II) and reaction time of 45 s), the increase in absorbance at 551 nm for DPD + generation was linear with respect to the addition of H 2 O 2 (0–12 μM). The sensitivity and the detection limit of the proposed Fenton-DPD method for H 2 O 2 determination at 551 nm were (2.55 ± 0.01) × 10 4  M −1  cm −1 and 0.05 μM, respectively. The stoichiometric factor for the reaction of H 2 O 2 with DPD was 1:1.18. The absorbance of the generated DPD + was found to be stable in different types of water within 20 min. Moreover, the proposed Fenton-DPD method could be used for the analysis of the trace H 2 O 2 in rainwater and determine the rate constants that involved H 2 O 2 with high accuracy.