Detection of melamine in infant formula and grain powder by surface‐assisted laser desorption/ionization mass spectrometry

We have developed a method for the determination of melamine (MEL), ammeline (AMN), and ammelide (AMD) by surface‐assisted laser desorption/ionization mass spectrometry (SALDI‐MS) using gold nanoparticles (Au NPs). The major peaks for MEL, AMN, and AMD at m/z 127.07, 128.05, and 129.04 are assigned to the MEL + H]⁺, AMN + H]⁺, and AMD + H]⁺ ions. Because the three tested compounds adsorb weakly onto the surfaces of the Au NPs through Au–N bonding, they can be easily concentrated from complex samples by applying a simple trapping/centrifugation process. The SALDI‐MS method provides limits of detection of 5, 10, and 300 nM for MEL, AMN, and AMD, respectively, at a signal‐to‐noise ratio of 3. The signal variation for 150‐shot average spectra of the three analytes within the same spot was 15%, and the batch‐to‐batch variation was 20%. We have validated the practicality of this approach by the analysis of these three analytes in infant formula and grain powder. This simple and rapid SALDI‐MS approach holds great potential for screening of MEL in foods. Copyright © 2012 John Wiley & Sons, Ltd.