Abstract: A gas chromatography-mass spectrometric (GC-MS) method has been established for the determination of cyromazine and its metabolite melamine in chickens. The homogenized tissue samples added with melamine-15N3 were extracted with acidic acetonitrile-water solution, and defatted with dichloromethane. The samples were derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA), after solid-phase extraction (SPE) which was performed on Oasis MCX cartridges, and then detected by GC-MS. Cyromazine was quantified by an external standard method, and melamine by an internal standard method using melamine-15N3. The results indicated that the linearities of cyromazine and melamine were within the range of 100~1000 μg/L, and their limits of quantification (LOQ) were 20 μg/kg. The mean recoveries of chicken samples fortified at three concentrations of 20, 40 and 80 μg/kg were within the range of 75%~110%. The relative standard deviations (RSDs) of intra- and inter- batch were less than 10% and 15%, respectively. The application of this method was further demonstrated by analyzing 10 real samples which were brought from local markets. The results show that this method is simple, rapid, sensitive and specific. It is appropriate for the identification and quantification of cyromazine and its metabolite melamine in chickens.

Key words: chicken , cyromazine, melamine, metabolite, residue, gas chromatography-mass spectrometry (GC-MS)