Simultaneous HPLC-PDA determination of commonly prescribed antidepressants and caffeine in sludge from sewage treatment plants and river sediments in the Itaipu reservoir region, Paraná, Brazil

Antidepressants are widely used in current times; therefore, they pose a potential risk to ecosystems through the disposal of domestic sewage, even after processing in treatment plants. This study proposes a fast method for the simultaneous determination of commonly used antidepressants (citalopram, venlafaxine, fluoxetine, sertraline, and amitriptyline) and caffeine as an anthropic marker, based on microwave-assisted solvent extraction followed by quantification using HPLC-DAD. The analytical method was validated and considered satisfactory for the simultaneous determination of the analytes in sewage sludge and sediments. No interferences were observed in the retention times of the analytes under study, indicating selectivity. Nevertheless, the study of the matrix effect revealed interference of the sludge and sediment matrices in the sensitivity and accuracy of the analytical method; therefore, calibration by standard addition was employed. The linearity was adequate for the concentration range of 50–800 ng mL⁻¹, with detection and quantification limits of 15–100 ng g⁻¹ and 100–250 ng g⁻¹, respectively. Precision was estimated to be less than 8% in terms of the coefficient of variation. Accuracy was assessed by fortification of sediment and sludge samples at three concentration levels and the recovery range varied from 60 to 99%. The developed and validated method was applied to samples of sewage sludge and sediments obtained from the Itaipu Reservoir region. The results confirm the presence of the analytes in the sewage sludge and indicate that treatment plant residue is a route of insertion of micropollutants into the local environment, because the antidepressants were also found in river sediments.