The Mechanism of Plasma Destruction of Enalapril and Related Metabolites in Water

A pulsed dielectric barrier discharge was used for the decomposition of enalapril, its metabolite, enalaprilat, its degradation by-product, diketopiperazine, as well as their combination, in aqueous solution. The discharge was generated at the interface between gas and the solution which flows as a film on the surface of the inner electrode of the plasma reactor. The degradation mechanism of the studied compounds and the temporal evolution of the reaction intermediates were established from LCMS analysis. A wide variety of degradation by-products were formed; at least six new derivatives, not mentioned in literature, were observed. However, most of these by-products were subsequently degraded to small molecules. The mineralization degree, determined from TOC and COD measurements, was approximately 40%.