Determination of the psychoactive drugs carbamazepine and diazepam in hospital effluent and identification of their metabolites.

This study addresses the occurrence of carbamazepine and diazepam and their metabolites in the wastewater of the University Hospital (HUSM) of the Federal University of Santa Maria, RS-Brazil. Samples were collected from three sampling points of the sewage treatment system: point A ('emergency effluent'), point B ('general effluent') and point C ('water course-receptor'). Eight metabolites were identified: carbamazepine-10-11-epoxide, 10-dihydro-carbamazepine, 2-OH-carbamazepine, iminoquinone, acridone, nordiazepam, oxazepam and temazepam. The mean concentrations in the emergency, general effluent and water course-receptor were as follows: 433.0 ± 4.7, 349.0 ± 5.0 and 485.0 ± 5.6 ng L(-1), for carbamazepine and 550.0 ± 4.3, 441.0 ± 7.9 and 586.6 ± 9.3 ng L(-1), for diazepam, respectively. Liquid chromatography with electrospray ionization tandem mass spectrometry (LC-QqLIT-MS) proved to be a method fit-to-purpose. The determination of carbamazepine and diazepam, and the identification of active metabolites showing environmental persistence (carbamazepine-10-11-epoxide, nordiazepam and oxazepam) revealed the need for a more effective treatment of the HUSM effluent. As far as we know, no similar study has been carried out on the wastewater of Brazilian hospitals.