Rapid identification of milk powder adulteration based on surface-enhanced Raman spectroscopy

In recent years, milk powder adulteration has emerged as a matter of great concern. In this study, a rapid, accurate, and efficient detection method based on surface-enhanced Raman spectroscopy (SERS) combined with principal component analysis (PCA) was established to detect milk powder adulteration. The "coffee ring" effect-based gold nanoparticles (Au NPs) as the SERS-enhancing substrate were coupled with a portable Raman spectrometer, which enabled the differentiation of various brands of milk powder and the detection of melamine in milk powder. The substrate exhibited good SERS enhancement ability with an enhancement factor of 104. Furthermore, a strong linear correlation with a correlation coefficient (R2) of 0.9903 was observed between the melamine Raman intensity and concentration from 0.5 to 5.0 mg/kg. The calculated limit of detection of melamine (LOD) was 0.15 mg/kg, while the limit of quantitation (LOQ) was 0.5 mg/kg. In addition, when the method was applied to the detection of melamine in milk powder samples, this method achieved the recovery rates of melamine in milk powder samples ranged from 92.83% to 98.86% with relative standard deviations between 0.84% and 1.14%. In summary, the established method offers the advantages of cost-effectiveness, less sample requirement, and shorter detection time, meeting the needs for milk powder classification and rapid melamine detection.