Radiation induced degradation of pharmaceutical residues in water: Chloramphenicol

The γ-radiolytic degradation of chloramphenicol (CPL) was investigated in 0.1–1mmoldm−3 aqueous solutions at various radiation conditions. The destruction of CPL was monitored by UV–vis spectrophotometric method through the decrease in the intensity of the absorbance band at 276nm. LC-MS/MS was used to identify the degradation products. Results indicate that •OH can add onto the CPL aromatic ring or can abstract H-atom from the side chain. The reductive dechlorination of CPL was also studied based on the reaction of eaq− with CPL. In 0.1mmoldm−3 solution above 2.5kGy dose complete CPL degradation was achieved. In the presence of dissolved oxygen at relatively low dose, various oxidation products were observed. In the presence of tertiary butanol radical scavenger tertiary butanol group containing products were also detected. The toxicity increased as a function of dose to 1.0kGy. At doses higher than 1.0kGy the toxicity decreased continuously due to further degradation. It was also demonstrated that the O2−•/HO2• pair has low reactivity in CPL solution. ► At 0.1mmoldm−3 concentration at 2.5kGy complete CPL degradation was observed. ► At 0.1mmoldm−3 concentration for mineralization 7–10kGy is needed. ► First stable products are molecules hydroxylated in the ring or in the side chain. ► The toxicity of the solutions goes through a maximum as a function of dose.