5-fluorouracil is one of the most frequently prescribed antineoplastic drugs, which is widely used since 40 years ago. 5-fluorouracil is a thymidylate synthase inhibitor; it can interrupt the enzyme of pyrimidine thymidine synthesis. A major source of 5-fluorouracil in surface water is released from wastewater treatment plants (WWTPs) and hospital effluents. Consequently, it is important to fully understand their fate in the natural system to predict the risk for exposure to these compounds. Many literatures have demonstrated that photodegradation is the most important degradation pathway in determining the natural fate of various pharmaceuticals. In natural photolysis system, dissolved organic matters (DOMs), nitrate and bicarbonate enhanced nitrate system were identified as significant photosensitizers. These substrates produce photoreactants, like triplet-state DOMs, singlet oxygen, hydroxyl radical, carbonate radicals, and other radical species (ROO�, eaq-) under sunlight.Bicarbonate is ubiquitous in the surface water, and has concentration range from 0.5~2.0 mM. With the changing climates, bicarbonate, from the vapor-liquid balance with carbon dioxide, may play an indispensable role in environmental water. In recent year, only a few researchers have found that bicarbonate can increase the photodegradation rate of target organic compounds in the absence of nitrate. However, the detailed mechanism of this degradation is not yet understood. In this study, photochemical interaction between 5-fluorouracil (in �g/L level) and bicarbonate was investigated. The half-life of 5-fluorouracil in Milli-Q water (direct photolysis) was 23.8�0.7 h, and in bicarbonate present (indirect photolysis) was shorten to 10.8�0.8 h under sunlight. Both direct photolysis and indirect photolysis of 5-fluorouracil produced a main hydration byproduct 5-fluoro-6-hydroxyhydrouracil. The detailed photo-reaction between 5-fluorouracil/5-fluoro-6-hydroxyhydrouracil and bicarbonate was examined.

Sunlight transformation of 5-Fluorouracil in aqueous environments in the presence of bicarbonate

248th National Meeting (2014)

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