Rapid detection of melamine in milk liquid and powder by surface-enhanced Raman scattering substrate array

• Only a simple dilution step is needed for analysis of melamine in real sample.
• Only a small volume of sample is required by cylindrical SERS substrate.
• Highly sensitive in detection of melamine without any drying procedure.
• The time for analysis of one sample can be shorter than 10 min.

To determine the artificial additives in dairy products, we demonstrate a simple method for rapid and massive determination of melamine in milk liquid and powder samples by surface-enhanced Raman spectroscopy (SERS) technique. The developed method utilizes silver nanoparticles (AgNPs) decorated on a cylindrical support for detecting as low as 5 μL of sample without any drying procedure. Importantly, the linear range for melamine in water was 5–400 parts per billion (ppb) with a low detection limit of 2.5 ppb (S/N = 3). In addition, for analysis of melamine in milk liquid and powder, the dilution method was successfully applied to suppress the matrix effect from real samples. Interestingly, our results indicate that a dilution factor of 75 could effectively reduce the matrix effect with partially sacrificing the sensitivity in detection. The detection limit is increased to 2 parts per million (ppm) in real sample detection, which is close to the acceptable limits regulated in milk products. More importantly, the elimination of complicated sample pre-treatments and the acceptable sensitivity in melamine detection attest our proposed method as a potential tool for rapid and massive food inspections.