Determination and photodegradation of sertraline residues in aqueous environment

Sertraline (SER) is an antidepressant of the selective serotonin reuptake inhibitor (SSRI) class that has been repeatedly reported in environmental matrices in the last decade. While the research has mostly dealt with the occurrence and toxicology of this compound, there is a lack of information pertaining to its transformation under environmental factors such as solar irradiation. The present study aimed to fill in these gaps by investigating sertraline photodegradation in laboratory scale experiments corroborated additionally by experiments on real surface water. The data, acquired by laboratory photodegradation with a medium pressure UV lamp in presence of photosensitizers or reaction quenchers, were used to predict SER phototransformation kinetics by means of the Aqueous Photochemistry of Environmentally occurring Xenobiotics (APEX) software. It was established that sertraline degrades by first-order kinetics mostly dominated by direct photolysis, while the presence of some of the reactive species including ·OH, CO3· and 3CDOM* could further accelerate the rate of the compound’s breakdown. The predicted results were validated using sertraline-spiked surface water, which was irradiated by actual sunlight, where the half-life of sertraline at around 1.4 days was estimated. Along with the photodegradation kinetics, we also identified five transformation products, three of which were successfully determined in Slovenian surface water samples. To the best of our knowledge, for two of these compounds our study represents the first report on their environmental occurrence. Overall, this work gives an insight into mechanisms of sertraline transformation in surface waters and demonstrates that photodegradation is a very important (and probably the main) transformation pathway for this contaminant.