Determination of Biurea in Flour and Flour Products by Isotope Dilution High Performance Liquid Chromatography-Tandem Mass Spectrometry

KeyWord:high performance liquid chromatography-tandem mass spectrometry£¨HPLC-MS/MS£©  isotope labeled internal standard  flour  flour products  biurea

Abstract:

      An isotope dilution high performance liquid chromatography-tandem mass spectrometric£¨HPLC-MS/MS£© method was established for the determination of biurea in flour and flour products.The biurea in certain matrices was extracted with ultrapure water,defatted with n-hexane when necessary,and then analyzed by HPLC-MS/MS.LC separation was performed on a Waters XBridge BEH Amide column£¨3.5 ¦Ìm£¬4.6 mm¡Á150 mm£© using ultrapure water and acetonitrile as mobile phase by gradient elution.Identification was achieved by electrospray ionization£¨ESI+£© in positive mode using multiple reaction monitoring.Quantification was performed by isotope labeled 13C2,15N2-biurea internal standard calibration.The calibration curve of biurea showed a good linearity in the range of 0.2-100 ¦Ìg/L with a correlation coefficient of 0.999 9.The average recoveries of biurea in flour,steamed bun,bread,deep-fried dough stick and noodle matrices£¨six aliquots for each level£© at three spiked levels ranged from 82.0% to 113.6%,with RSDs of 2.1%-9.3%.The LOQ of the methed was 20 ¦Ìg/kg.The optimized method was successfully applied in the analysis of 136 real samples collected from local markets in Southern China£¬while biurea residues were found in 42£¨30.88%£© samples,of which 43.7-564 ¦Ìg/kg of biurea existed in 4 flours,70.8-9 840 ¦Ìg/kg in 2 noodles,2 480 ¦Ìg/kg in 1 deep-fried dough stick,27.4-8 730 ¦Ìg/kg in 15 breads-crust and 64.3-18 100 ¦Ìg/kg in 20 breads-interior.This method is applicable for the determination of biurea in flour and different flour products due to its operation convenience,high sensitivity and good accuracy.