title: Ozonation of chlortetracycline in the aqueous phase: Degradation intermediates and pathway confirmed by NMR.
abstract: Chlortetracycline (CTC) degradation mechanism in aqueous phase ozonation was evaluated for degradation mechanism and its correlation with the biodegradability and mineralization. CTC was removed within 8 and 4 min of ozonation at pH 2.2 and 7.0, respectively. At pH 2.2, HPLC-triple quadrupole mass spectrometry (MS) detected 30 products. The structures for some of these products were proposed on the basis of ozonation chemistry, CTC structure and MS data; these structures were then confirmed by nuclear magnetic resonance (NMR) spectra. Double bond cleavages, dimethyl amino group oxidation, opening and removal of the aromatic ring and dechlorination, mostly direct ozonation reactions, gave products with molecular weights (m.w.) 494, 510, 524, 495 and 413, respectively. Subsequent degradations gave products with m.w. 449, 465, 463 and 415. These products were arranged into a degradation pathway. At pH 7.0, the rate of reaction was increased, though the detected products were similar. Direct ozonation at pH 2.2 increased the biodegradability by altering the structures of CTC and its products. Nevertheless, direct ozonation alone remained insufficient for the mineralization, which was efficient at pH 7.0 due to the production of free radicals.
authors.affiliation: Department of Environmental Engineering, Yeungnam University, 280 Daehak-Ro, Gyeongsan-si, Gyeongsangbuk-do 38541, Republic of Korea.
authors.forename: M Hammad
authors.initials: MH
authors.lastname: Khan
authors.affiliation: Department of Environmental Engineering, Yeungnam University, 280 Daehak-Ro, Gyeongsan-si, Gyeongsangbuk-do 38541, Republic of Korea. Electronic address: jinjung@ynu.ac.kr.
authors.forename: Jin-Young
authors.initials: JY
authors.lastname: Jung
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000378:metabolism; D001673:Biodegradation, Environmental; D002751:Chlortetracycline / Q000737:chemistry / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D010126:Ozone / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D014874:Water Pollutants, Chemical; D010126:Ozone; D002751:Chlortetracycline
keywords: Chlortetracycline; Degradation mechanism; MS data; NMR spectra; Ozonation