Comparison among the Methods for Hydrogen Peroxide Measurements To Evaluate Advanced Oxidation Processes:  Application of a Spectrophotometric Method Using Copper(II) Ion and 2,9-Dimethyl-1,10-phenanthroline

Hydrogen peroxide (H2O2) in the range of several tens to several hundreds of micromoles per liter is usually added to the process water in advanced oxidation processes (AOPs). In this study, a spectrophotometric method using copper(II) ion and 2,9-dimethyl-1,10-phenanthroline (DMP) for measuring H2O2 concentration was compared with other methods [i.e., spectrophotometric methods using titanium oxalate and N,N-diethyl-p-phenylenediamine (DPD) and a fluorometric method using p-hydroxyphenyl acetic acid (POHPAA)]. Particular attention was paid to sensitivities and effects of coexisting substances. The most sensitive method was the fluorometric method, followed in order by DPD, DMP, and the titanium oxalate colorimetric method; their detection limits in 1-cm cells were 0.16, 0.77, 0.80, and 29 μM, respectively. Therefore, the DMP method was found to be reasonably sensitive when applied to AOPs. Also, the DMP reagent is commercially available, and the absorbance of Cu(DMP)2 +, a reaction product of the DMP method, was not affected by reaction time. In the DMP method, copper(II)−DMP complexes react with humic acid, and colored chemicals are produced. However, the slopes of the calibration curves of H2O2 containing up to 10 mg of C L-1 from humic acid did not change significantly as compared to that in ultrapure water. The effect of chlorine on the DMP method was not observed up to at least 23 μM (0.8 mg of Cl L-1) of free chlorine, although the DPD and fluorometric methods are known to be interfered by chlorine. From this study, it was concluded that the DMP method is suitable to be used in AOPs.