Exploring the aquatic photodegradation of two ionisable fluoroquinolone antibiotics – Gatifloxacin and balofloxacin:Degradation kinetics, photobyproducts and risk to the aquatic environment

Ge, Linke and Halsall, Crispin and Chen, Chang-Er and Zhang, Peng and Dong, Qianqian and Yao, Ziwei (2018) Exploring the aquatic photodegradation of two ionisable fluoroquinolone antibiotics – Gatifloxacin and balofloxacin:Degradation kinetics, photobyproducts and risk to the aquatic environment. Science of the Total Environment, 633. pp. 1192-1197. ISSN 0048-9697

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Abstract

Fluoroquinolone antibiotics (FQs) are ubiquitous and ionisable in surface waters. Here we investigate gatifloxacin (GAT) and balofloxacin (BAL), two widely used FQs, and determine the photochemical reactivity of their respective dissociation species that arise at different pH to understand the relevance and pathways of phototransformation reactions. Simulated-sunlight experiments and matrix calculations showed that neutral forms (HFQs0) of the two antibiotics had the highest apparent photolytic efficiency and hydroxyl-radical oxidation reactivity. Based on the pH-dependent photochemical reactivities, the solar apparent photodegradation half-lives (t1/2) in sunlit surface waters ranged from 14.5–169 min and was 1–2 orders of magnitude faster than hydroxyl-radical induced oxidation (t1/2 = 20.9–29.8 h). The corresponding pathways were proposed based on the identification of key intermediates using HPLC-ESI-MS/MS. The apparent photodegradation induced defluorination, decarboxylation, and piperazinyl oxidation and rearrangement, whereas hydroxyl-radical oxidation caused hydroxylated defluorination and piperazinyl hydroxylation. The photomodified toxicity of GAT and BAL was examined using an Escherichia coli activity assay. E. coli activity was not affected by BAL, but was significantly affected by the photo-modified solutions of GAT, indicating that primary photo-degradates have a comparable or higher antibacterial activity than the parent GAT. In fresh water and seawater this antibacterial activity remained high for up to 24 h, even after GAT had undergone significant photodegradation (>1 half-life), indicating the potential impact of this chemical on microbial communities in aquatic systems.

Item Type:
Journal Article
Journal or Publication Title:
Science of the Total Environment
Additional Information:
This is the author’s version of a work that was accepted for publication in Science of the Total Environment. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Science of the Total Environment 633, 2018 DOI: 10.1016/j.scitotenv.2018.03.279
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/2300/2311
Subjects:
ID Code:
124316
Deposited By:
Deposited On:
18 Apr 2018 15:26
Refereed?:
Yes
Published?:
Published
Last Modified:
28 Nov 2020 05:19