Photocatalytic Degradation of Metoprolol Tartrate

The advanced oxidation of high purity metoprolol tartrate, extracted from a commercial medicament, with TiO₂ and UV light (365 nm) was investigated to determine the effect of initial reactant concentration on the reaction rate and the role of direct photolysis on the photocatalytic process. Analysis of the reaction samples by UV–Vis spectroscopy indicated that metoprolol tartrate is efficiently degraded by photocatalysis via hydroxylation of the aromatic ring. Kinetic studies indicated that the photocatalytic degradation of metoprolol tartrate follows a Langmuir, Hinshelwood, Hougen and Watson (LHHW) mechanism where the reaction order shifts from zero order to first order as the reactant concentration drops. Additional experiments showed that direct photolysis plays a minor role on the photocatalytic oxidation of metoprolol tartrate. Total organic carbon (TOC) studies demonstrated that metoprolol tartrate is transformed to other organic intermediate reaction products before complete mineralization to CO₂. The fraction of reactant transformed into intermediate organic products was evaluated by a material balance using the results of analysis of the reaction samples by high performance liquid chromatography and TOC.