Degradation of antidepressant pharmaceuticals by photoperoxidation in diverse water matrices: a highlight in the evaluation of acute and chronic toxicity.

Photoperoxidation (UV/H ₂ O ₂ ) was used to degrade three of the worldwide most consumed antidepressant pharmaceuticals-bupropion, escitalopram, and fluoxetine-in ultrapure water, drinking tap water, surface water, and reclaimed water. The study was performed with antidepressants in concentration levels in which these compounds usually occur in the water matrices. Online solid-phase extraction coupled to UHPLC-MS/MS was used to quantify the analytes during degradation studies. The UV/H ₂ O ₂ process was able to degrade bupropion and fluoxetine in ultrapure water, using 0.042 mmol L ^-1 of H ₂ O ₂ and 1.9 kJ of UV-C irradiation. Nevertheless, escitalopram, which had the most recalcitrant character among the studied antidepressants, needed a tenfold more oxidant and UV-C irradiation. The primary metabolites of the antidepressants were identified as the major by-products generated by the UV/H ₂ O ₂ process, and they persisted in the solution even when the parent compound was degraded. The residual toxicity of the solution was evaluated for two different trophic levels. The UV/H ₂ O ₂ process reduced the toxicity of the solution to Raphidocelis. subcapitata microalgae after 30 min of reaction. On the other hand, the toxicity of the residual solution increased over the reaction time to the marine bacteria Vibrio fischeri (reaching up to 48.3% of bioluminescence inhibition after 60 min of reaction). Thus, our results evidenced that the toxicity against different trophic levels and the monitoring of the by-products formed are important aspects to be considered regarding the safety of the treated solution and the optimization of the treatment process.