Supervisors info:
Νικόλαος Θωμαΐδης Αναπληρωτής Καθηγητής (Επιβλέπων), Αντώνιος Καλοκαιρινός Καθηγητής, Μιχαήλ Κουππάρης Καθηγητής
Summary:
Biodegradation is considered to be the key process for the elimination of the
majority of pharmaceuticals in the environment. During wastewater treatment or
once they are disposed in the aquatic environment, pharmaceuticals may be
transformed to new, structurally-related compounds which are called
transformation products (TPs). Since most of these compounds are unknown, their
identification is essential not only to provide a comprehensive risk assessment
on micropollutants in the environment, but also to design improved removal
technologies for (pseudo)persistent trace contaminants.
In this study, batch reactors seeded with activated sludge from the
wastewater-treatment plant (WWTP) of Athens were set up to assess biotic,
abiotic and sorption losses of the drug, citalopram (CTR). TPs were identified
by reversed-phase liquid chromatography quadrupole-time-of-flight mass
spectrometry (RPLC-QTOF-MS). Hydrophilic interaction liquid chromatography
(HILIC) was also used as a complementary, orthogonal, technique for the
identified TPs. A workflow for suspect and non-target screening was developed.
Structure elucidation of TPs was based on accurate mass and isotopic pattern
measurements and interpretation of MS/MS spectra by the observed fragmentation
pattern and literature data.
In total, fourteen TPs were identified and a transformation pathway based on
the identified compounds was presented. Four out of them were confirmed by
corresponding reference standards (N-desmethylCTR, CTR amide, CTR carboxylic
acid and 3-oxo-CTR). A probable structure based on diagnostic evidence was
proposed for the additional nine TPs, whereas only an unequivocal molecular
formula was assigned to the last one. After the identification, the presence of
the fourteen TPs was investigated in wastewater samples.
Keywords:
Citalopram, Biodegradation, Transformation products, RPLC-QTOF-MS, HILIC
