Effect of O₃/H₂O₂ molar concentration ratio at different pH values on cyclophosphamide degradation

The effect of O₃/H₂O₂ liquid phase molar concentration ratio at different pH on cyclophosphamide degradation rate was evaluated. The combination of O₃/H₂O₂ leads to an increase of cyclophosphamide degradation rate, compared with single ozonation at the same pH and ozone dosages. It was found that cyclophosphamide degradation rate with O₃/H₂O₂ depends on pH for the molar concentration ratios under study, the fastest degradation being observed for molar concentration ratio near 3.4 at pH 7 (80% degradation in 3 minutes). Pseudo-first order reaction rate constants for cyclophosphamide degradation were determined under the experimental conditions of this study. Cyclophosphamide was not detected after 15 minutes of reaction, but only a partial mineralization was obtained, evidenced by a total organic carbon removal lower than 60%. By attenuated total reflection infrared spectroscopy and electrospray ionization tandem mass spectrometry, 4-ketocyclophosphamide was identified as one of the main reaction products at pH 7 and 3.4 molar concentration ratio.