The degradation and persistence of five pharmaceuticals in an artificial climate incubator during a one year period

Abstract

The degradation and persistence of the five pharmaceuticals atenolol, metoprolol, propranolol, fluoxetine and venlafaxine at an initial concentration of 10 mg L-1 was studied at different pH values under fluorescent light and darkness in an artificial climate incubator during a one-year period. The results suggested that the degradation process of the target pharmaceuticals followed pseudo first-order degradation kinetics. Propranolol was degraded at a higher rate, with a half-life ranging from 5.7 to 28.5 d. The degradation rates of propranolol and venlafaxine increased with increasing pH value, while the other pharmaceuticals did not show a clear pH correlation, with the highest degradation rate at pH 7 for atenolol, pH 2 for metoprolol and pH 12 for fluoxetine. Both photodegradation and hydrolysis should contribute to the degradation. Typical transformation products were detected and were identified as metoprolol acid, α-hydroxymetoprolol, norfluoxetine and O-desmethylvenlafaxine. The findings could not only help to understand the degradation and fate of pharmaceuticals but also provide the fundamental data for persistence assessments.