Characterisation by high-performance liquid chromatography–multiple mass spectrometry of intermediate compounds formed from mepanipyrim photoinduced degradation

Mepanipyrim, a widely used pyrimidinic fungicide, has been photocatalytically degraded in aqueous solution on TiO2. The purpose of this study is to artificially produce degradation compounds similar to those formed in the environment. Numerous intermediates have been identified and characterised through a MSn spectra analysis, allowing us to give insight into the early steps of the degradation process. Several concomitant pathways occur concerning both reductive and/or oxidative attacks; the main steps involve the cleavage of triple bond, mono and bihydroxylation of the parent molecule, loss of benzene moiety and/or propynylic chain. All these structures are easily degraded themselves, so that the only species recognised to endure in the investigated times is guanidine. A mechanism of transformation accounting for the identified intermediates is proposed.