Chromatographic separation and detection of contaminants from whole milk powder using a chitosan-modified silver nanoparticles surface-enhanced Raman scattering device

- We developed a method to separate and detect multiple components simultaneously.
- Ag NPs was deposited on Ch/paper to form the flexible SERS-active substrate.
- Detection of separated contaminants was achieved with a portable Raman spectrometer.
- The limit of detection of MEL was 1 mg/L.

Methods for the on-site analysis of food contaminants are in high demand. Although portable Raman spectroscopy is commonly used to test food on-site, it can be challenge to achieve this goal with rapid detection and inexpensive substrate. In this study, we detected trace food contaminants in samples of whole milk powder using the methods that combined chromatography with surface-enhanced Raman scattering detection (SERS). We developed a simple and efficient technique to fabricate the paper with chitosan-modified silver nanoparticles as a SERS-active substrate. The soaking time of paper and the concentration of chitosan solution were optimized for chromatographic separation and SERS detection. We then studied the separation properties for real applications including complex sample matrices, and detected melamine at 1 mg/L, dicyandiamide at 100 mg/L and sodium sulfocyanate at 10 mg/L in whole milk powder. As such, our methods have great potential for field-based detection of milk contaminants.