Abstract: Objective: To develop a TLC-SERS method for the simultaneous quantitative detection of four Sudan dyes in hot pepper products by the combined use of thin-layer chromatography (TLC) and surface-enhanced Raman spectroscopy (SERS). Methods: Silver nanoparticles were prepared by silver mirror reaction and loaded onto silica gel plates for TLC. The experimental conditions such as silver nanoparticle size, loading conditions, and droplet volume were optimized. Separation before detection was adopted as a strategy to simultaneously quantify four structurally similar Sudan red dyes in hot pepper products. Results: The characteristic peaks of Sudan red I-IV dyes showed a good linear relationship with their concentrations in the range of 1-200 mg/L, with determination coefficients (R2) of 0.996, 0.995, 0.993, and 0.992, respectively. When applied in practice, the proposed method exhibited a detection limit (LOD) of 1 mg/L for all four dyes. The recoveries of these dyes in hot pot base and chili products ranged from 89.8% to 96.2%, indicating good accuracy and reliability of this method. Conclusion: This method is low-cost, simple, fast, sensitive and accurate, and has good application prospects for the on-site detection of Sudan red I-IV dyes.

Key words: thin-layer chromatography; surface-enhanced Raman spectroscopy; simultaneous detection; Sudan red I-IV dyes