Determination of Melamine and Cyanuric Acid Residues in Infant Formula using LC-MS/MS

A liquid chromatography triple quadrupole tandem mass spectrometry (LC-MS/MS) method for residues of cyanuric acid (CYA) and melamine (MEL) developed by the Center for Veterinary Medicine (CVM) has been adapted for use with infant formula. This method consists of an initial extraction with 2.5% aqueous formic acid, followed by a series of filtration, centrifugation, and dilution steps. Both compounds are analyzed in the same chromatographic program using a zwitterionic HILIC LC column. Electrospray ionization is used in both the negative ion (CYA) and positive ion (MEL) modes. Two selected reaction monitoring (SRM) transitions are monitored for both compounds. The amount of compounds present is determined with a calibration curve consisting of sample extracts from infant formula fortified from 0.25 to 5 μg/g that have been taken through the extraction procedure. The range of recovery from fortified infant samples (n =38) was 70-114 % (RSDs 4.522.7 %), and 72-110% (RSDs 5.7-24.9%) for cyanuric acid and melamine, respectively. The limits of quantification and confirmation are 0.25 μg/g for both analytes in dry infant formula.