[Simultaneous determination of 11 mycotoxins in malt by isotope internal standard-UPLC-MS/MS]

A suitable ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) method was developed for the determination of 11 mycotoxins with isotope internal standard in malt. The mycotoxins in malt were extracted and purified by one-step ultrasonic extraction procedure using acetonitrile/water/acetic acid (80 : 19 : 1), and then detected and confirmed by UPLC-MS/MS, and quantified by isotope labeled AFB1 ([13C17]-AFB1) and ZEN ([13C18]-ZEN) internal standards. Rapid separation of the 11 mycotoxins was successfully achieved on a Phenomenex Kinetex C18 column (100 mm x 2.1 mm, 2.6 μm) with gradient elution using the mobile phase of methanol containing 0.1% formic acid and 2 mmol x L(-1) ammonium acetate in water. Simultaneous acquisition was performed in multiple reaction monitoring (MRM) mode with electrospray ionization (ESI) source operated in both positive and negative ionization modes. The established method provided a good linearity for the 11 mycotoxins within their respective linear ranges with correlation coefficients all higher than 0.999 1. The average recoveries ranged from 75.0% to 117.0% with relative standard deviations (RSDs) below 5.1%. The limits of detection (LODs) and quantitation (LOQs) ranged from 0.05 to 30 μg x kg(-1) and 0.15 to 87.5 μg x kg(-1), respectively, which were below the maximum residue levels (MRLs) set by the European Union. Twenty malt samples were analyzed and nine samples were detected with mycotoxins, which were confirmed according to the same fragment ions found in positive samples and the standards at the same retention time. This study has demonstrated that the one-step extraction procedure of mycotoxins from complex matrices coupled to UPLC-MS/MS method is simple, quick, accurate and sensitive for quantitative and qualitative analysis of multiple mycotoxins in malt.