Photochemical degradation of the carbapenem antibiotics imipenem and meropenem in aqueous solutions under solar radiationPhotochemical degradation of the carbapenem antibiotics imipenem and meropenem in aqueous solutions under solar radiation Peer-Reviewed Journal Publication Δημοσίευση σε Περιοδικό με Κριτές 2019-11-132018enThis paper deals with the photochemical fate of two representative carbapenem antibiotics, namely imipenem and meropenem, in aqueous solutions under solar radiation. The analytical method employed for the determination of the target compounds in various aqueous matrices, such as ultrapure water, municipal wastewater treatment plant effluents, and river water, at environmentally relevant concentrations, was liquid chromatography coupled with hybrid triple quadrupole-linear ion trap-mass spectrometry. The absorption spectra of both compounds were measured in aqueous solutions at pH values from 6 to 8, and both compounds showed a rather strong absorption band centered at about 300 nm, while their molar absorption coefficient was in the order from 9 × 103–104 L mol−1 cm−1. The kinetics of the photochemical degradation of the target compounds was studied in aqueous solutions under natural solar radiation in a solar reactor with compound parabolic collectors. It was found that the photochemical degradation of both compounds at environmentally relevant concentrations follows first order kinetics and the quantum yield was in the order of 10−3 mol einsten−1. Several parameters were studied, such as solution pH, the presence of nitrate ions and humic acids, and the effect of water matrix. In all cases, it was found that the presence of various organic and inorganic constituents in the aqueous matrices do not contribute significantly, either positively or negatively, to the photochemical degradation of both compounds under natural solar radiation. In a final set of photolysis experiments, the effect of the level of irradiance was studied under simulated solar radiation and it was found that the quantum yield for the direct photodegradation of both compounds remained practically constant by changing the incident solar irradiance from 28 to 50 W m−2.http://creativecommons.org/licenses/by/4.0/Water Research128January 201861-70 Reina Alejandro Cabrera Martínez-Piernas Ana Belén Bertakis Ioannis Μπερτακης Ιωαννης Brebou Christina Μπρεμπου Χριστινα Xekoukoulotakis Nikos Ξεκουκουλωτακης Νικος Agüera Ana Sánchez Pérez José Antonio Elsevier Carbapenem antibiotics Imipenem Meropenem Photolysis Quantum yield Solar radiation