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Kinetic study of photochemical degradation of the pharmaceutical substance fluoxetine in aqueous solutions

Papadogiannis Georgios

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Summary

The current thesis deals with the kinetic study of photochemical degradation of the pharmaceutical substance fluoxetine in aqueous solutions. Fluoxetine is an antidepressant and belongs in a class called selective serotonin reuptake inhibitors. The degradation of the substance occurred using direct UV-C photolysis with a wavelength of 254 nm. Furthermore the photochemical degradation of the substance using hydrogen peroxide as an oxidizing agent was also studied.The laboratory experiments were conducted with an 11 W, low pressure mercury lamp emitting at 254 nm. UV-C irradiation experiments were carried out in a small scale batch reactor. The volume of the reactor was 450 mL. During the experiments, the aqueous mixture was at room temperature with constant pH (7). Samples were periodically collected from the reactor and the concentration of fluoxetine, oxidizing agent (H2O2) and total organic carbon were measured.A series of direct photolysis experiments were conducted to investigate the effects of initial concentration of fluoxetine to the rate of the direct photolysis.. The range of initial concentrations that was studied was from 2.9 μmolL to 86.8 μmolL. The results of these experiments show that the rate of the direct photolysis of fluoxetine remained practically constant by varying the initial concentration of fluoxetine.These results indicate that, the photochemical degradation of fluoxetine is a first-order reaction. The reaction rate constant and the quantum yield were also calculated.From the above mentioned experiments was also found that the complete degradation of fluoxetine using UV-C radiation is relatively fast (takes up to 5-6 minutes). Furthermore the total organic carbon measurements show minimum mineralization.Finally a series of indirect photolysis experiments using hydrogen peroxide as an oxidizing agent were conducted. The above mentioned experiments showed that hydrogen peroxide drastically affects the degradation, notably the reaction time was even faster (1-4 minutes). However the total organic carbon measurements show that the mineralization was incomplete.

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