Ozonation of propranolol: formation of oxidation products

Major oxidation products (OPs) of the beta blocker propranolol, formed during ozonation in aqueous solution were identified and oxidation pathways were proposed. Ozonation led to a high number of OPs being formed. In total, chemical structures were elucidated for five different nominal masses (including constitutional isomers, approximately 13 signals), whereas at least eight other OPs and their isomers (approximately 30 signals) remained unidentified. The structural elucidation was performed via liquid chromatography coupled with hybride triple quadrupole with linear ion trap (LC-Qq LIT MS). The primary ozonation product OP-291, was formed by ozone attacking the naphthalene ring, which resulted in the ring-opening and two aldehyde moieties being formed. OP-291 was further oxidized to OP-307, which was then oxidized to OP-281. Experiments were performed at pH 3 and pH 8, as well as in the presence and absence of a radical scavenger. Ozonation of wastewater treatment plant (WWTP) effluents spiked with propranolol (10 microM) led to the same OPs being formed as observed in the experiments with deionized water. Therefore, ozonation of WWTP effluent is resulting in the formation of a high number of OPs with an elevated toxic potential (i.e., formation of aldehydes).