Abstract: A method for the determination of cyanuric acid in milk and milk powder has been developed by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) with post-column ammoniation. After extracted by 5% trichloroacetic acid, the samples were loaded onto an Acquity UPLC HSS T3 column (50 mm×2.1 mm, 1.8 μm) and separated with a gradient elution. The electrospray was operated in the negative mode and monitored by the multiple reaction monitoring (MRM) mode. The calibration curves showed a good linearity in the range of 10.0~160.0 μg/L, and the correlation coefficients (r) were higher than 0.99. When the spiked levels were 0.05, 0.10, and 0.20 mg/kg, the recoveries of cyanuric acid in milk ranged from 60% to 118.5%, with the relative standard deviations (RSDs) of 8.2%~12.6%; while the spiked levels were 0.25, 0.50, and 1.00 mg/kg in the milk powder, the recoveries ranged from 88% to 108% and the RSDs ranged from 2.5%~5.7%. The limits of quantification (LOQs, S/N=10) of cyanuric acid were 0.05 mg/kg in milk sample and 0.25 mg/kg in milk powder. The results indicate that the method is simple, rapid, sensitive and suitable for the qualitative and quantitative analyses of cyanuric acid in milk and milk powder samples.

Key words: cyanuric acid, milk, milk powder, ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), post-column ammoniation