A sensitive and selective method for the determination of flumorph residues in vegetables and fruits by HPLC–ESI-MS/MS

A method has been developed and validated for the quantitative determination of flumorph residues in vegetables and fruits using dimoxystrobin as internal standard (I.S.) by high performance liquid chromatography–tandem mass spectrometry (LC–MS/MS). The conversion rule between flumorph (Z) and flumorph (E) has been studied through sunlight photodegradation test of flumorph. Flumorph and I.S. were extracted with ethyl acetate and preconcentrated by Oasis HLB cartridge. Qualitative and quantitative detection for the analytes were carried out under the multiple reaction monitoring (MRM) in positive ionization mode after chromatography separation on a Symmetry C18 (150 mm × 2.1 mm × 3.5 μm) column. Studies at fortification level of 0.05–25 μg kg−1 gave mean recoveries from 77.6 to 92.9% for flumorph, with relative standard deviation (R.S.D.) ≤8.7%. The limit of quantification (LOQ, S/N = 10) was 0.05 μg kg−1. The proposed method was successfully applied on real samples from different kinds of vegetables and fruits. Flumorph residues were detected in 70% of the samples analyzed and the highest concentration level was 1.83 μg kg−1 in tomato sample.