Degradation of antineoplastic cytarabine in aqueous phase by advanced oxidation processes based on ultraviolet radiation

The aim of this study was to determine the effectiveness of oxidation processes based on cytarabine degradation using UV radiation (UV, UV/H2O2, and UV/K2S2O8). Results show that UV radiation alone is not effective to remove cytarabine from the aqueous medium, due to the low quantum yield of this molecule (Φλ = 6.88 × 10−6 mol Einstein−1). The addition of H2O2 or K2S2O8 considerably increased the removal effectiveness due to the generation of HO and SO4− radicals. The reaction rate constants between cytarabine and HO radicals and SO4− radicals were kHOcyst = 3.15 × 1010 m−1 s−1 and kSO4−cyt=1.61×109 M−1 s−1kSO4−cyt=1.61×109 M−1 s−1. For both systems (UV/H2O2 and UV/K2S2O8), (i) an decrease in the pH of solution reduces the cytarabine removal rate, (ii) a specific concentration of H2O2 and K2S2O8 produces the highest cytarabine removal rate, (iii) the chemical composition of water considerably affects the cytarabine oxidation rate, especially in the UV/H2O2 system, mainly due to the lesser selectivity and greater reactivity of the HO radical, and (iv) the total organic carbon concentration in the medium decreased with longer treatment time but the toxicity increased, especially in the case of the UV/H2O2 system.