title: Lorazepam photofate under photolysis and TiO2-assisted photocatalysis: identification and evolution profiles of by-products formed during phototreatment of a WWTP effluent.
abstract: This manuscript reports on the study of Lorazepam (LZP) phototransformation pathways under artificial UV and natural solar irradiation, through photolytic and TiO2-assisted photocatalytic processes. Three experimental set-ups were employed: two lab-scale photoreactors, each provided with an UV lamp (one medium pressure mercury lamp and one blacklight blue lamp), and a pilot-scale Solar Plant with Compound Parabolic Collectors (CPCs). Samples collected along the different phototreatment experiments were analyzed by ultra-high performance liquid chromatography-quadrupole-time-of-flight-mass spectrometry (UHPLC/QqToF-MS). The key assumption of the analytical approach was that related compounds (LZP and its by-products (LBPs)) provide identical "diagnostic fragment ions". Identification was also based on the chlorine atoms specific isotopic pattern, as well as accurate masses. Six major LBPs were identified and elucidated, with nominal [M + H](+) masses of 337, 303, 319, 275, 291 and 293 Da. The proposed LZP photodegradation mechanism included the initial opening of the diazepinone seven-membered ring, followed by a rearrangement into a highly stabilized six-membered aromatic ring and subsequent cleavage and/or hydroxylation reactions. The evolution profiles of LBPs were described for each of the three experimental prototypes and the CPCs Solar Pilot Plant proved to be the most efficient one. Finally, LZP photocatalytic degradation was further assessed on a municipal effluent, where the photoproducts generated showed to be more persistent than LZP itself.
authors.affiliation: Department of Bromatology and Hydrology, Faculty of Pharmacy, University of Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal; IAREN - Water Institute of the Northern Region, Rua Dr. Eduardo Torres 229, 4450-113 Matosinhos, Portugal.
authors.forename: M A
authors.initials: MA
authors.lastname: Sousa
authors.forename: O
authors.initials: O
authors.lastname: Lacina
authors.forename: P
authors.initials: P
authors.lastname: Hrádková
authors.forename: J
authors.initials: J
authors.lastname: Pulkrabová
authors.forename: Vítor J P
authors.initials: VJ
authors.lastname: Vilar
authors.forename: C
authors.initials: C
authors.lastname: Gonçalves
authors.forename: Rui A R
authors.initials: RA
authors.lastname: Boaventura
authors.forename: J
authors.initials: J
authors.lastname: Hajšlová
authors.forename: M F
authors.initials: MF
authors.lastname: Alpendurada
mesh_terms: D002384:Catalysis; D007700:Kinetics; D008140:Lorazepam / Q000737:chemistry*; D010782:Photolysis; D014025:Titanium / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D014874:Water Pollutants, Chemical; C009495:titanium dioxide; D014025:Titanium; D008140:Lorazepam
keywords: By-products; CPCs solar pilot plant; Lorazepam; TiO(2)-photocatalysis; Ultra-high performance liquid chromatography–high resolution mass spectrometry