Quantification of fenitrothion and its main metabolites in poplar leaves by isotope dilution gas chromatography–mass spectrometry coupled with solid-phase microextraction

A sensitive and specific method for determining fenitrothion and its main metabolites, 3-methyl-4-nitrophenol and fenitrooxon, in poplar leaves using deuterated isotopes as the internal standard is described. The analytes and the labeled isotopes were extracted from leaves by solid-phase microextraction and subsequently analysed by gas chromatography coupled with mass spectrometry. The method had a chromatographic run time of 17.0 min and good linearity over the range 0.01–10 mg kg−1. The detection limits ranged between 2.5 and 0.6 μg kg−1. The isotopic dilution technique allowed improving significantly the repetitivity even using different fibers with the same coating (RSD < 5.1%). The method was applied successfully to study the persistence of fenitrothion in forestal matrices in a poplar forest after cannon spray application of the insecticide.