Determination of Fumonisins B₁, B₂ and B₃ in Tea by Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry with QuEChERS

After crushing and sieving the tea sample, an aliquot (2.50 g) was taken, and 2.0 mL of water was added for wetting. Then 20 mL of acetonitrile solution containing 1% (volume fraction) formic acid was added, and the mixture was vortexed for 3 min, and centrifuged at 4℃ for 10 min. An aliquot (1.0 mL) of the supernatant was taken and placed into a 2.0 mL-centrifuge tube containing the purifiers (250 mg of anhydrous magnesium sulfate and 150 mg of multiple walled carbon nanotubes). The mixture was vortexed for 3 min, and centrifuged at 4℃ for 10 min. The supernatant was collected, and passed through a 0.22 μm organic phase filter membrane. The initial filtrate was discarded, and the subsequent filtrate was analyzed by ultra-high performance liquid chromatography-tandem mass spectrometry. In chromatographic analysis, Agilent Poroshell 11 chromatographic column was used as the stationary phase, and mixed solutions composed of 0.1% (volume fraction) formic acid solution and acetonitrile at different volume ratios were used as the mobile phase for gradient elution separation. In mass spectrometry analysis, electrospray ion source positive ion (ESI⁺) mode was used for ionization, and multiple reaction monitoring (MRM) mode was used for detection. It was shown that linear relationships between values of the mass concentration of fumonisins B₁, B₂, and B₃ and the corresponding peak area were kept in the range of 0.5-100.0 μg·L^-1, with detection limits (3S/N) in the range of 0.15-1.00 μg·kg^-1. Test for recovery was made according to the standard addition method, giving recoveries in the range of 82.1%-108%, and RSDs (n=6) of the determined values ranged from 2.7% to 5.3%. The proposed method was used for the analysis of 50 batches of tea samples, and fumonisin B₁ was detected in a batch of black tea sample, with detection amount of 8.321 μg·kg^-1.