New spectrophotometric method for the quantitative determination of melamine using Mannich reaction

The objective of this study was to develop a spectrophotometric method for the quantitative determination of melamine. The method was based on the complexation of melamine with a mixture of formaldehyde and chemicals including a ketone group, as described by the Mannich reaction. The complex was determined by spectrophotometric absorption measurement as it is characterized by specific spectroscopic properties that are related to the chromophore of the ketone compounds. Uranine was tested as a ketone compound. The UV spectrum of the complex presented a maximum of absorption at 214 nm. An internal standard was added to quantify the melamine. The method was tested to determine the level of melamine in food, using a contaminated fish sample from China. The recovery value was 97% and the limit of detection was 0.063 μg/mL.