Influence of interfering dissolved organic matter on the determination of hydrogen peroxide by a colorimetric method based on the peroxidase catalyzed oxidation of N,N-diethyl-p-phenylenediamine.

The influence of dissolved organic matter (DOM), such as humic acid (HA) and hydroxybenzoic acids, on the determination of H(2)O(2) via a colorimetric method using N,N-diethyl-p-phenylenediamine (DPD) was examined. The influence of DOM on absorbance decay at 551 nm, which represents the wavelength for maximum absorption of the oxidized species of DPD (DPD(+)), were investigated in detail. Significant decrease in the absorbance at 551 nm was observed in the presence of HA and gallic acid. This resulted in a fadeout of the purple color of DPD(+), which, in term, created great difficulties in the measurement of H(2)O(2) in solutions which contain DOM. To remove DOM prior to the addition of coloring reagents, a diethylaminoethyl Sephadex A-25 ion exchanger was used prior to the analysis for pre-separation. It was found that this pre-separation was useful in the DPD colorimetric determination of H(2)O(2) the solution which contain DOM.