Aqueous photochemical behavior of oxazolidinone antibiotic linezolid

Abstract

Photochemical degradation is a central factor in determining the fate of antibiotic micropollutants in surface waters. In this study, the photodegradation kinetics, influencing factors and transformation products of linezolid, a representative oxazolidinone antibiotic, were investigated. Under simulated sunlight irradiation ( λ >290 nm), the photodegradation followed the pseudo-first-order kinetics with an apparent quantum yield of 0.834±0.054 in pure water. The rates of linezolid photodegradation were slower in freshwater or seawater than in pure water, which was attributed to the effects of the ubiquitous aqueous dissolved matter on the photodegradation. pH, Cl– and seawater salinity did not affect the photodegradation kinetics ( P >0.05), while humic acid, NO3− and Fe(III) acted mainly as radiation filters and inhibited the photodegradation ( P ≤0.05). Under simulated sunlight as well as UV-vis ( λ >200 nm) irradiation, scavenging experiments revealed that linezolid underwent direct photolysis and self-sensitized photodegradation via 1O2, which resulted in a negative correlation between the photolysis rate constants and the initial concentrations. The main photodegradation products and pathways varied under irradiation of different light sources. Linezolid mainly underwent defluorination and photoinduced hydrolysis under UV-vis irradiation, whereas morpholine-dehydrogen was primary under simulated sunlight.