When analyzed by HPLCeUV methods, false-positive results often occurred. That was because the UV absorption
wavelength of melamine was usually set at 240 nm, the wavelength at which many compounds also had UV absorption. Some studies indicated that amino acids might interfere with the melamine peak when analyzed by HPLCeUV. In this study, 10 kinds of milk samples were analyzed by the proposed method to study the possible interferences. No melamine was found in these samples, and of course no interference peaks were observed. Mixed standard solutions of 20 amino acids were then studied under the same conditions. The MASC derivatives of amino acids showed no interference with melamine derivative. For milk sample chromatogram in Fig. 2, the unknown peaks at retention times of 2e3 min and 7.5 min were caused by amino acids, while the other peaks might be caused by compounds containing amino or phenolic hydroxyl groups which could also reacted with MASC. No interference was observed in water sample analysis, either. Therefore, the proposed method is much less hindered bycommon interferences which are often observed in HPLCe UV method. Its superiority would be more evident when analyzing
milk or other analytes with complex matrices.