TY - JOUR

T1 - Direct UV photodegradation of nalidixic acid in aqueous solutions: A mechanistic study

AU - Tyutereva, Yuliya E

AU - Snytnikova, Olga A

AU - Fedunov, Roman G

AU - Yanshole, Vadim V

AU - Plyusnin, Victor F

AU - Xu, Jing

AU - Pozdnyakov, Ivan P

N1 - The financial support of the Russian Science Foundation (Grant RSF - NSFC № 21-43-00004 ) and the National Natural Science Foundation of China (Grant NSFC-RSF 22 061 132 001 ) is gratefully acknowledged. The authors also thank the Ministry of Science and Higher Education of the RF for the access to the LC/MS equipment. Copyright © 2023 Elsevier Ltd. All rights reserved.

PY - 2023/9

Y1 - 2023/9

N2 - Mechanism of direct UV photolysis of nalidixic acid (NA), a model quinolone antibiotic, was revealed using a combination of steady-state photolysis coupled with high resolution LC-MS and DFT quantum-chemical calculations. Both quantum yields of photodegradation and detailed identification of final products were performed for the first time for two main forms of NA: neutral and anionic. The quantum yield of NA photodegradation is 0.024 and 0.0032 for the neutral and anionic forms in the presence of dissolved oxygen and 0.016/0.0032 in deoxygenated solutions, respectively. The main process is photoionization with the formation of a cation radical, which undergoes transformation into three different neutral radicals and further into final photoproducts. It is shown that the triplet state does not play a role in the photolysis of this compound. The main products of photolysis are the products of the loss of carboxyl, methyl and ethyl groups in the NA molecule, as well as the dehydrogenation of the ethyl group. The results obtained may be important for understanding the fate of pyridine herbicides in the processes of disinfection by UV and in natural waters under the action of sunlight.

AB - Mechanism of direct UV photolysis of nalidixic acid (NA), a model quinolone antibiotic, was revealed using a combination of steady-state photolysis coupled with high resolution LC-MS and DFT quantum-chemical calculations. Both quantum yields of photodegradation and detailed identification of final products were performed for the first time for two main forms of NA: neutral and anionic. The quantum yield of NA photodegradation is 0.024 and 0.0032 for the neutral and anionic forms in the presence of dissolved oxygen and 0.016/0.0032 in deoxygenated solutions, respectively. The main process is photoionization with the formation of a cation radical, which undergoes transformation into three different neutral radicals and further into final photoproducts. It is shown that the triplet state does not play a role in the photolysis of this compound. The main products of photolysis are the products of the loss of carboxyl, methyl and ethyl groups in the NA molecule, as well as the dehydrogenation of the ethyl group. The results obtained may be important for understanding the fate of pyridine herbicides in the processes of disinfection by UV and in natural waters under the action of sunlight.

KW - Kinetics

KW - Nalidixic Acid

KW - Photolysis

KW - Sunlight

KW - Water Pollutants, Chemical/analysis

KW - Water/chemistry

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-85160445118&origin=inward&txGid=1189948d09b4418da0100372d1d95df7

U2 - 10.1016/j.chemosphere.2023.138952

DO - 10.1016/j.chemosphere.2023.138952

M3 - Article

C2 - 37201608

VL - 334

JO - Chemosphere

JF - Chemosphere

SN - 0045-6535

M1 - 138952

ER -