Photoproducts of tetracycline and oxytetracycline involving self-sensitized oxidation in aqueous solutions: Effects of Ca2+ and Mg2+ |
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Authors: | Yong Chen Hua Li Zongping Wang Tao Tao and Chun Hu |
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Institution: | 1. School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China 2. State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences, Beijing 100085, China |
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Abstract: | Tetracyclines constitute one of the most important antibiotic families and represent a classic example of phototoxicity. The photoproducts of tetracyclines and their parent compounds have potentially adverse effects on natural ecosystem. In this study, the self-sensitized oxidation products of tetracycline (TC) and oxytetracycline (OTC) were determined and the effects of Ca2+ and Mg2+on self-sensitized degradation were investigated. The Ca2+ and Mg2+ in the natural water sample accounted for enhancement (pH 7.3) and inhibition (pH 9.0) of photodegradation of TC and OTC due to the formation of metal-ions complexes. The formation of Mg2+ complexes was unfavorable for the photodegradation of the tetracyclines at both pH values. In contrast, the Ca2+ complexes facilitated the attack of singlet oxygen (1O2) arising from self-sensitization at pH 7.3 and enhanced TC photodegradation. For the first time, self-sensitized oxidation products of TC and OTC were verified by quenching experiments and detected by LC/ESI-DAD-MS. The products had a nominal mass 14 Da higher than the parent drugs (designated M+14), which resulted from the 1O2 attack of the dimethylamino group on the C-4 atom of the tetracyclines. The presence of Ca2+ and Mg2+ also affected the generation of M+14 due to the formation of metal-ions complexes with TC and OTC. The findings suggest that the metal-ion complexation has significant impact on the self-sensitized oxidation processes and the photoproducts of tetracyclines. |
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Keywords: | tetracyclines complexation self-sensitized oxidation photoproducts |
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