Fluorometric determination of low concentrations of H2O2 in water: Comparison with two other methods and application to environmental samples and drinking-water treatment

Three different analytical methods for the determination of low concentrations of H2O2 in surface and tap water were compared. A flow injection method based on the enzymatic catalyzed reduction of H2O2 in the presence of p-hydroxyphenylacetic acid (POHPAA) and with a fluorometric registration of the resulting fluorochrome exhibited lowest limits of detection (0.2 μg·l−1) and of determination (0.8 μg·l−1). The photometric determination of H2O2 by the peroxidase-catalyzed oxidation of N,N-diethyl-p-phenylendiamine (DPD method) was less sensitive, while the procedure based on the photometry of the complex formed with titanyl oxalate was insensitive for H2O2 concentrations lower than 24 μg·l−1. Ozone and chlorine (oxidants used in drinking-water treatment) and dissolved organic matter (DOM) interfere in the formation of the fluorescence intensity signal. Ozone was shown to generate H2O2 in aqueous solutions containing p-hydroxyphenylacetic acid and peroxidase. In order to determine the concentration of H2O2 in this case, the fluorescence caused by the amount of freshly generated H2O2 should be estimated in a separate experiment and should be subtracted from the total fluorescence intensity signal. Also determinations of water containing DOM should be corrected for the emission of fluorescence caused by the DOM itself.