Determination of Antidepressants in Portuguese Wastewater

Antidepressants are among the most widely prescribed pharmaceutical compounds worldwide and are increasingly recognised as contaminants of emerging concern owing to their occurrence in wastewater as parent compounds and metabolites. Their continuous release into aquatic systems reinforces the need for reliable analytical methods for environmental monitoring. In this study, a solid-phase extraction coupled with gas chromatography-tandem mass spectrometry method was developed and validated for the determination of five antidepressants in wastewater: fluoxetine, citalopram, sertraline, paroxetine, and venlafaxine. Different extraction conditions were assessed in order to improve analytical performance. Method validation was carried out according to Food and Drug Administration guidelines. The method showed good linearity over the concentration range of 49–25,000 ng/L, with coefficients of determination higher than 0.99. Limits of detection ranged from 12 to 195 ng/L, while limits of quantification ranged from 49 to 195 ng/L. Precision and accuracy were within acceptable limits, with coefficients of variation below 15%, and recoveries ranged from 6.91% to 81.14%. Most analytes remained stable under the tested conditions. The method was successfully applied to 50 real wastewater samples, confirming its applicability to the routine monitoring of antidepressants in this complex environmental matrix.