The metabolic pathway of flonicamid in oranges using an orthogonal approach based on high-resolution mass spectrometry and nuclear magnetic resonance

Abstract

An orthogonal approach has been used to perform a metabolic profiling study of flonicamid in orange fruits. Nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS) have been applied to monitor the degradation pathway of flonicamid into its metabolites in field and laboratory studies. 4-Trifluoromethylnicotinic acid (TFNA) and 4-(trifluoromethyl)nicotinol glycine (TFNG) were detected after 15 days of flonicamid application in field studies, whereas in laboratory trials, TFNG was found in oranges after 70 days of flonicamid application. The results were confirmed through the use of one-dimensional ¹H, ²H and ¹⁹F NMR, observing the formation of TFNG as well as the detection of N-(4-trifluoromethylnicotinoyl)glycinamide (TFNG-AM) as a transient species, which is also a known flonicamid metabolite. The deuteration of the methylenic carbon of both flonicamid and TFNG was also observed, and as a matter of a fact, exploited for the first time as a route for selective isotope labeling. Orthogonal techniques, such as high-resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR) have been applied for the first time in the study of the metabolic pathway of flonicamid in oranges. Thus, a comprehensive view of the transformation process has been achieved taking advantage of the possibilities of both techniques.