Degradation of imidacloprid in water by photo-Fenton process using UV-LED lamps at neutral pH: Study of intermediate products by liquid chromatography mass spectrometry after dispersive liquid–liquid microextraction

Abstract

In the present study, a suitable analytical method to determine imidacloprid (IMI) and its main transformation products (TPs) in water by means of dispersive liquid–liquid microextraction (DLLME) combined with liquid chromatography coupled to mass spectrometry (LC-MS), using both quadrupole-time-of-flight (QTOF) and triple quadrupole (QqQ) analysers, has been developed. In addition, the structures of major products formed when IMI is photo-oxidized using ultraviolet A (UVA) irradiation with light emitting diode (LED) lamps were established. Finally, the behaviour of IMI and its main TPs generated in water during photo-Fenton processes at neutral pH using two ferric iron complexes, with ethylenediamine-N,N-disuccinic acid (EDDS) and nitrilotriacetic acid (NTA) as chelating agents, was studied. DLLME was found to efficiently preconcentrate IMI and IMI TPs from the water matrix using chloroform (as extractant solvent) and acetonitrile (as dispersant solvent) in a simple step. The selectivity of the used techniques provided unequivocal identification of IMI and its TPs and their quantification with high sensitivity during the photo-Fenton treatments. In addition, the photo-Fenton treatment using EDDS exhibited higher degradation rate than photo-Fenton treatment using NTA.