Monitoring of the photochemical degradation of metamitron and imidaclopridby micellar electrokinetic chromatography and differential-pulse polarography

The photochemical degradation of metamitron (4-amino-4,5-dihydro-3-methyl-6 -phenyl-1,2,4-triazin-5-one) and imidacloprid (1-(6-chloro-3-pyridylmethyl) -N-nitroimidazolidin-2-ylideneamine) has been investigated by differential- pulse polarography (DPP) and micellar electrokinetic chromatography (MEKC); the degradation pathways of these pesticides were elucidated and their deg radation products proposed. The electrochemical study of imidacloprid by DPP at different pH values dem onstrated the occurrence of two different reduction processes; at pH 6.8, t wo peaks at -0.90V and -1.38V, respectively, were obtained, which are relat ed to the photochemical reduction processes. The photochemical degradation of imidacloprid caused by sunlight was polarographically monitored and its degradation products elucidated. The polarographic reduction of deaminometa mitron (obtained by photochemical reduction of metamitron) yielded two peak s at -0.62 and -1.37V, which are related to the reduction of the C=N bonds. The effect of sunlight on the reduction of metamitron was monitored by DPP , and an increase of the concentration of the degradation products was obse rved with time. MEKC with W-visible detection was used to separate the pesticides and the p roducts of their photochemical degradation, which were identified in combin ation with DPP. (C) 1999 Society of Chemical Industry.