Simultaneous Determination of Isofetamid and Its Two Metabolites in Fruits and Vegetables Using Ultra-Performance Liquid Chromatography with Tandem Mass Spectrometry

In this paper, an efficient analytical method for the simultaneous determination of a new fungicide (isofetamid) and its two metabolites in fruits and vegetables was developed using the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) pretreatment method and ultra-performance liquid chromatography-tandem mass spectrometry. The three compounds were extracted with acetonitrile and cleaned up using primary secondary amine, octadecylsilane, and graphitized carbon black. The three analytes were well separated with good specificity using an electrospray ionization source in positive mode within 5.0 min. The mean recoveries in apple, strawberry, grape, tomato, cucumber, and lettuce for the three target compounds at different levels ranged from 74 to 107%, with relative standard deviations lower than 12.3%. The method showed excellent linearity (R2 ≥ 0.9946) for the three compounds. The limits of quantification of isofetamid and its metabolites were 1 μg kg−1 in apple, tomato, and cucumber and 100 μg kg−1 in strawberry, grape, and lettuce. The proposed method was successfully applied to a residue dynamic experiment, and it can be considered a strong alternative method to monitor the residues of isofetamid and its metabolites simultaneously in fruits and vegetables.