The Study Of Photolytic Behavior Of Naproxen In Aqueous Environment

Naproxen (NPX) is a synthetic non-steroidal anti-inflammatory drug (NSAID) and is. mostly used in its sodium salt form in medical care as an analgesic, antiarthritic and antirheumatic. As it enters the aquatic environment by direct or indirect emission, NPX was detected in a variety of environmental water. Its presence at low or high concentrations could bring about harmful toxicological consequences. For instance, people who ingest trace amounts of NPX for a long time may have a higher risk of having a heart attack or a stroke than people who are not exposed to this medication. Consequently, it is clear that much attention should be paid on NPX in the aquatic environment. Photochemical reaction is an important pathway for degradation and transformation2of naproxen in surface water. This paper investigated the photodegradation kinetics, photodegradation mechanisms, photodegradation pathways and photoproducts and studied the effects of different concentrations of nitrate, nitrite and ammonium ion on photodegradation of NPX under simulated sunlight. Photodegradation experiment on NPX was performed in pure water under irradiation of different light sources. The results indicated that NPX could be degraded effectively under simulated sunlight and UV irradiation, and the process of NPX photodegradation could be fitted by the pseudo first-order kinetics model. These criteria were investigated by conducting quenching experiments with reactive oxygen species (ROS) and oxygen concentration experiments. The results indicated that the degradation of naproxen included degradation by direct photolysis and by self-sensitization via ROS in the aquatic environment, and direct photodegradation contributed to the main degradation of NPX with little contributed of self-sensitization. The toxicity evaluation illustrated that some of the intermediate products formed were more toxic than NPX.We also studied the different influences on photodegradation of NPX with different concentrations of nitrate, nitrite, ammonium ions, and different pE values when these three forms of N elements coexisted. The result showed that nitrate and nitrite inhibited the degradation of NPX under simulated sunlight, and the higher the concentration, the more pronounced the inhibitory effect, due to the absorption wavelength overlaps the absorbance wavelength region of NPX. Ammonium ions have no effect on the photodegradation of NPX. On the one hand, the ammonium ion has no light absorption in the UV-visible range. On the other hand, the ammonium ion will not produce ROS by light irradiation to promote the photolysis of NPX. Photodegradation rate of NPX in the presence of different forms of nitrogen changes with different pE values in the aquatic environment under simulated sunlight were investigated. The results show that the photodegradation rate of NPX decreased first, then increased, and different forms of nitrogen coexist in the aquatic environment had an obvious antagonistic action.Seven intermediates were detected by HPLC/MS/MS and GC/MS. which were2-ethyl-6-methoxynaphthalene;1-(6-methoxynaphthalen-2-yl)ethanol;2-ethenyl-6-methoxynaphthalene;1-(6-methoxynaphthalen-2-yl)ethanone;1-(5-hydroxy-6-methoxy-naphthalen-2-yl)ethanone:1-(5.8-dihydroxy-6-methoxynaphthalen-2-yl)ethanone;6-ethenyl-2-methoxynaphthalene-1.4-dione;2-methoxynaphthalen-l-ol;1-(6-methoxy-naphthalen-2-y])ethyl acetate. Moreover, we speculated degradation pathway for NPX under simulated sunlight.