Photochemical behaviour of propranolol in environmental waters: the hydroxylated photoproducts

The UV irradiation of propranolol, one of the beta-blockers currently used in cardiac medicine, was studied. During irradiation, the samples were analysed by LC/MS/MS, using a Waters Symmetry C₁₈ (3.5?µm 150?×?2.1?mm) column. The main photoproducts were identified from mono-, di- and tri-hydroxylation of the propranolol naphthalenic skeleton. Hydroxyl group positions were predicted by means of theoretical calculations. Partial charge calculations of the propranolol atoms predicted the formation of four mono-hydroxylated compounds, two of them being the most probable. From these two compounds, three di-hydroxylated compounds were predicted. Then the calculations from the two most probable di-hydroxylated compounds were used to propose three tri-hydroxylated propranolol compounds. It was found that the same hydroxylated photoproducts are formed in pure water and in treatment plant waste water.