Rapid and sensitive detection of melamine in milk with gold nanoparticles by Surface Enhanced Raman Scattering

A rapid and sensitive method to detect melamine in liquid milk based on Surface Enhanced Raman Scattering (SERS) spectroscopy is presented, exploiting the selective binding of gold nanoparticles (AuNPs) with this analyte. This interaction promotes the aggregation of the AuNPs inducing a huge enhancement of the melamine signals in the Raman spectrum due to the formation of SERS "hot spots". An external standard calibration method was employed for quantitative analysis and the method was validated for linearity, sensitivity, repeatability and recovery. A good linearity (R2 = 0.99) was found in the concentration range of 0.31-5.0 mg l-1 in milk with a limit of detection of 0.17 mg l-1. This method does not require a long extraction procedure (total analysis time can be lower than 30 min) and can be reliably used for melamine detection in milk matrix in accordance with the European law limits.