Abstract:

A novel method was established for the determination and identification of biurea in flour and its products using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The biurea was extracted with water and oxidized to azodicarbonamide by potassium permanganate. The azodicarbonamide was then derivatized using sodium p-toluene sulfinate solution. The separation was performed on a Shimpak XR-ODSⅡ column (150 mm×2.0 mm, 2.2 μm) using the mobile phase composed of acetonitrile and 2 mmol/L ammonium acetate aqueous solution (containing 0.2% (v/v) formic acid) with a gradient elution program. Tandem mass spectrometric detection was performed in multiple reaction monitoring (MRM) scan mode with a positive electrospray ionization (ESI⁺) source. The method used stable isotope internal standard quantitation. The calibration curve showed good linearity over the range of 1-20000 μg/kg(R²=0.9999). The limit of quantification was 5 μg/kg for biurea spiked in flour and its products. At the spiking levels of 5.0, 10.0 and 50.0 μg/kg in different matrices, the average recovery of biurea was 78.3%-108.0% with the relative standard deviations (RSDs)≤5.73%. The method developed is novel, reliable and sensitive with wide linear range, and can be used to determine the biurea in flour and its products.

Key words: p-toluenesulfonyl semicarbazide, azodicarbonamide, biurea, derivatization, flour, flour products, liquid chromatography-tandem mass spectrometry (LC-MS/MS)