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.