Abstract: A method for the determination of melamine in milk and milk products was established by joint use of HPLC-PAD with external standard quantification and UPLC-MS/MS with internal standard quantification. Melamine content of samples was primarily analyzed by HPLC-PAD with external standard quantification, and then confirmed by UPLC-MS/MS and quantified by internal standard method using 13C315N3. Samples were extracted with acetonitrile and then the extract was added with zinc acetate and hydrochloric acid and cleaned up using an MCX solid-phase extraction cartridge prior to UPLC-MS/MS analysis. The limit of quantification of the HPLC-PAD method was 4 mg/kg, while that of the UPLC-MS/MS method was 0.05 mg/kg. The average recovery rates of melamine from milk powder, liquid milk and milk cream across three spike levels as determined by the HPLC-PAD and UPLC-MS/MS methods were 95.7%–102.3% and 91.3%–95.7% (matrix match calibration), respectively, and the relative standard deviations were 1.98%–4.51% and 1.60%–3.27%.

Key words: melamine, high performance liquid chromatography-photodiode array detection (HPLC-PAD), ultra-high performance liquid chromatography-electrospray ionization tandem mass spectrometry (UPLC-MS/MS) , internal standard method, milk products