Photometric method for the determination of low concentrations of hydrogen peroxide by the peroxidase catalyzed oxidation of N,N-diethyl-p-phenylenediamine (DPD)

The concentration of hydrogen peroxide (H2O2) in distilled water, drinking water and in different types of surface and rain waters can be easily determined by a photometric method in which N,N-diethyl-p-phenylenediamine (DPD) is oxidized by a peroxidase catalyzed reaction. DPD is available as a commercial reagent. In all waters its oxidation occurs with a stoichiometric factor of 2.0 and leads to an absorbance (at 551 nm) of 21,000 ± 500 M−1cm−1 per H2O2. In the presence of other hydroperoxides H2O2 can be determined by comparison with a blank in which the H2O2 is destroyed with sulfite, and the sulfite residual masked with formaldehyde. The detection limit is 0.2 μg l−1 in distilled water and about 0.3 μg l−1 in most types of natural waters when 10 cm cells and a spectrophometer are used. We consider the DPD method to be a candidate for a standard method for drinking water analysis because it is easy to perform and to calibrate for absolute determinations.