Determination of Metabolites of Nitrofurans Residues in Casing by Ultra Performance Liquid Chromatography-Electrospray Tandem Mass Spectrometry

A comprehensive analytical method based on ultra performance liquid chromatography-electrospray ionization mass spectrometry(UPLC-MS /MS) with positive mode has been developed for the determination of metabolites of nitrofurans residues in casing.The multi-reaction monitoring mode was employed for the determination.Casing samples were defatted and preliminary purified with methanole and water,and then hydrolyzed with hydrochloric acid and derived with 2-NBA at 37 ℃ for 16 hours.Sample solutions was concentrated and purified by Oasis HLB solid phase extraction cartridges.The separation was performed on a Waters ACQUITY UPLCTM BEH C18(1.7 μm,2.1 mm×50 mm)column with gradient elution using 0.3% acetic acid acetonitrile and 0.3% acetic acid water at a flow rate of 0.4 mL/min.Identification of metabolites of nitrofurans was done using the retention times and the distribution of diagnostic ion pairs;the precursor/product ion transitions were monitored.Quantification of the metabolites of nitrofurans by the peak areas of higher signal precursor/production.The limits of detection(LOD) of the method was 0.2~0.5 μg/kg.The recoveries were between 86%~97%.The relative standard deviations were below 10%.