Study of the simulated sunlight photolysis mechanism of ketoprofen: the role of superoxide anion radicals, transformation byproducts, and ecotoxicity assessment

Abstract

The aim of this study was to investigate the photolysis mechanism of ketoprofen (KET) under simulated sunlight. The results demonstrated that the photolysis of KET aligned well with pseudo first-order kinetics. Radical scavenging experiments and dissolved oxygen experiments revealed that the superoxide anion radical (O˙) played a primary role in the photolytic process in pure water. Bicarbonate slightly increased the photodegradation of KET through generating carbonate radicals, while DOM inhibited the photolysis via both attenuating light and competing radicals. Moreover, Zhujiang river water inhibited KET phototransformation. Potential KET degradation pathways were proposed based on the identification of products using LC/MS/MS and GC/MS techniques. The theoretical prediction of reaction sites was derived from Frontier Electron Densities (FEDs), which primarily involved the KET decarboxylation reaction. The ecotoxicity of the treated solutions was evaluated by employing Daphnia magna and V. fischeri as biological indicators. Ecotoxicity was also hypothetically predicted through the "ecological structure-activity relationship" (ECOSAR) program, which revealed that toxic products might be generated during the photolysis process.

The Impact of Dissolved Organic Matter on Photodegradation Rates, Byproduct Formations, and Degradation Pathways for Two Neonicotinoid Insecticides in Simulated River Waters

“…Further, significant differences were observed between treatments with TEMPOL compared to NaN 3 and IPA (α ≤ 0.05), which indicate that the addition of TEMPOL significantly inhibited the degradation processes of both imidacloprid and thiamethoxam, while the treatments with NaN 3 and IPA significantly enhanced the degradation of imidacloprid and thiamethoxam. Wang et al [42] observed similar occurrences following the addition of TEMPOL, which significantly inhibited the degradation process of ketoprofen, while isopropanol had a negligible effect on the degradation process [42].…”

“…According to Wang et al [42], during the photolysis process of pharmaceutical and personal care products (PCPs) ROS, such as 1 O 2 , • OH, and O 2…”

“…TEMPOL, NaN 3 , and IPA were utilized as quenching agents. These quenching agents were used to specifically determine whether imidacloprid and thiamethoxam underwent self-sensitization though ROS during the photolysis process in the different waters under simulated sunlight [42]. Details can be found in Supplementary Materials (Equations (S2)-(S5)).…”

Essential role of sunlight irradiation in aqueous micropollutant transformations: influence of the water matrix and changes in toxicities

“…114 The photodegradation pathway and reaction sites were theoretically predicted by frontier electron densities, indicating that the decarboxylation reaction of ketoprofen and its product is the most toxic. 134 As for DBPs, dehalogenation was the main transformation pathway that is relevant to toxicity change during photolysis processes due to DBPs containing a halide which is of high electronegativity resulting in uneven distribution of charges. Take CH 2 I 2 for example, the toxicities of the phototransformation products of Daphnia magna LC 50 and oral rat LD 50 were decreased compared to that of the parent molecule.…”

“…114 The photodegradation pathway and reaction sites were theoretically predicted by frontier electron densities, indicating that the decarboxylation reaction of ketoprofen and its product is the most toxic. 134…”