TY - JOUR
T1 - Photolytic and photocatalytic decomposition of aqueous ciprofloxacin
T2 - Transformation products and residual antibacterial activity
AU - Paul, Tias
AU - Dodd, Michael C.
AU - Strathmann, Timothy J.
N1 - Funding Information:
This article was developed under a STAR Research Assistance Agreement No. 91683701-0 awarded by the U.S. Environmental Protection Agency to T. Paul. It has not been formally reviewed by the EPA. The views expressed in this document are solely those of the authors and the EPA does not endorse any products or commercial services mentioned in this publication. Financial support was also provided to M.C. Dodd by a U.S. National Science Foundation Graduate Fellowship and the project RECLAIM WATER (Contract No. 018309) – funded through the Sixth Framework Programme of the European Commission. Additional support was provided by the National Science Foundation Division of Chemical, Bioengineering, Environmental, and Transport Systems (CBET-0746453) and the Center of Advanced Materials for the Purification of Water with Systems (CTS-0120978). Furong Sun (UIUC SCS Mass Spectrometry Laboratory) is acknowledged for assistance with mass spectrometry analysis. Urs von Gunten is gratefully acknowledged for his helpful suggestions in reviewing the manuscript.
PY - 2010/5
Y1 - 2010/5
N2 - Previous work demonstrates that widely used fluoroquinolone antibacterial agents, including ciprofloxacin, are degraded by means of aqueous ultraviolet photolytic and titanium dioxide (TiO2) photocatalytic (using both ultraviolet-A (UVA) and visible light (Vis) irradiation) treatment processes. In this study, we investigate the effects of photolytic and photocatalytic treatment processes on the antibacterial activity of ciprofloxacin solutions under controlled laboratory conditions. In agreement with earlier work, rates of ciprofloxacin degradation under comparable solution conditions (100μM ciprofloxacin, 0 or 0.5g/L TiO2, pH 6, 25°C) follow the trend UVA-TiO2>Vis-TiO2>UVA. Release of ammonia and fluoride ions is observed and a range of organic products have been identified with liquid chromatography-tandem mass spectrometry. However, the identified organic products all appear to retain the core quinolone structure, raising concerns about residual antibacterial potency of the treated solutions. Quantitative microbiological assays with a reference Escherichia coli strain indicate that the antimicrobial potency of ciprofloxacin solutions track closely with the undegraded ciprofloxacin concentration during photolytic or photocatalytic reactions. Quantitative analysis shows that for each mole of ciprofloxacin degraded, the antibacterial potency of irradiated solutions decreases by approximately one " mole" of activity relative to that of the untreated ciprofloxacin solution. This in turn indicates that the ciprofloxacin photo(cata)lytic transformation products retain negligible antibacterial activity relative to the parent compound. The energy demands for achieving one order of magnitude reduction in antibacterial activity within the experimental system are estimated to be 175J/cm2 (UVA-only), 29J/cm2 (Vis-TiO2), and 20J/cm2 (UVA-TiO2), which indicates that the UVA-TiO2 photocatalysis is the most energy efficient process for achieving ciprofloxacin inactivation under laboratory conditions.
AB - Previous work demonstrates that widely used fluoroquinolone antibacterial agents, including ciprofloxacin, are degraded by means of aqueous ultraviolet photolytic and titanium dioxide (TiO2) photocatalytic (using both ultraviolet-A (UVA) and visible light (Vis) irradiation) treatment processes. In this study, we investigate the effects of photolytic and photocatalytic treatment processes on the antibacterial activity of ciprofloxacin solutions under controlled laboratory conditions. In agreement with earlier work, rates of ciprofloxacin degradation under comparable solution conditions (100μM ciprofloxacin, 0 or 0.5g/L TiO2, pH 6, 25°C) follow the trend UVA-TiO2>Vis-TiO2>UVA. Release of ammonia and fluoride ions is observed and a range of organic products have been identified with liquid chromatography-tandem mass spectrometry. However, the identified organic products all appear to retain the core quinolone structure, raising concerns about residual antibacterial potency of the treated solutions. Quantitative microbiological assays with a reference Escherichia coli strain indicate that the antimicrobial potency of ciprofloxacin solutions track closely with the undegraded ciprofloxacin concentration during photolytic or photocatalytic reactions. Quantitative analysis shows that for each mole of ciprofloxacin degraded, the antibacterial potency of irradiated solutions decreases by approximately one " mole" of activity relative to that of the untreated ciprofloxacin solution. This in turn indicates that the ciprofloxacin photo(cata)lytic transformation products retain negligible antibacterial activity relative to the parent compound. The energy demands for achieving one order of magnitude reduction in antibacterial activity within the experimental system are estimated to be 175J/cm2 (UVA-only), 29J/cm2 (Vis-TiO2), and 20J/cm2 (UVA-TiO2), which indicates that the UVA-TiO2 photocatalysis is the most energy efficient process for achieving ciprofloxacin inactivation under laboratory conditions.
KW - Antibacterial potency
KW - Fluoroquinolones
KW - Microbiological assay
KW - Photo-deactivation
KW - Photolysis
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U2 - 10.1016/j.watres.2010.03.002
DO - 10.1016/j.watres.2010.03.002
M3 - Article
C2 - 20363011
AN - SCOPUS:77952548070
SN - 0043-1354
VL - 44
SP - 3121
EP - 3132
JO - Water Research
JF - Water Research
IS - 10
ER -