Photo-transformation of acetaminophen sensitized by fluoroquinolones in the presence of bromide

Fluoroquinolones (FQs) are a class of antibiotics with emerging concern. This study investigated the photo-chemical properties of two representative FQs, i.e., norfloxacin (NORF) and ofloxacin (OFLO). Results showed that both FQs could sensitize the photo-transformation of acetaminophen under UV-A irradiation, during which excited triplet state (3FQ*) was the main active species. In the presence of 3 mM Br acetaminophen increased by 56.3% and 113.5% in the solutions with 10 mu M NORF and OFLO, respectively. Such an effect was ascribed to the generation of reactive bromine species (RBS), which was verified by 3,5-dimethyl-1H-pyrazole (DMPZ) probing approach. 3FQ* reacts with acetaminophen through one-electron transfer, pro-ducing radical intermediates which then couple to each other. Presence of Br brominated products but the same coupling products, which suggests that radical bromine species, rather than free bromine, were responsible for the accelerated acetaminophen transformation. According to the identified reaction products and assisted with the theoretical computation, the transformation pathways of acetaminophen under UV-A irradiation were proposed. The results reported herein suggest that sunlight-driven reactions of FQs and Br , the photolysis rate of ? did not lead to the formation of ? may influence the transformation of coexisting pollutants in surface water environments.

Automated summary

This study investigated the photo-chemical properties of two representative fluoroquinolones (FQs), norfloxacin (NORF) and ofloxacin (OFLO). Both FQs were found to sensitize the photo-transformation of acetaminophen under UV-A irradiation, with excited triplet state (3FQ*) as the main active species. The presence of bromine ions resulted in an increased transformation of acetaminophen, indicating the involvement of reactive bromine species (RBS). The identified reaction products and theoretical computation proposed the transformation pathways of acetaminophen under UV-A irradiation.