Schiff base reaction-assisted SERS internal standard strategy for highly sensitive and accurate detection of vanillin derivatives in tea matrices

Background Vanillin (4-hydroxy-3-methoxybenzaldehyde), an aromatic compound derived from vanilla pods. Currently, it is widely used as an additive in the food industry due to its unique aroma and flavor. However, excessive consumption of vanillin can cause nausea, dizziness, allergies and vomiting. Various methods have been established to detect vanillin content, including electrochemistry, gas chromatography (GC), fluorescence analysis. These methods exhibit good sensitivity in vanillin detection but are limited by complex pretreatment steps, time consumption, and expensive equipment. Thus, it is critical to develop a sensitive, rapid, simple, and low-cost method for monitoring vanillin concentration in food. Results In this work, a Schiff base reaction-assisted SERS internal standard detection method is proposed for the highly sensitive detection of vanillin in tea. Ag nanocubes (Ag NCs) are functionalized with 4-aminothiophenol (4-ATP), whose amino group undergoes a Schiff base reaction with the aldehyde group of vanillin to form a stable C N imine group. Highly sensitive detection of vanillin is achieved by identifying the C N stretching vibration peak. Using the C S stretching vibration peak as an internal standard, a linear relationship is established. The results show that this method requires no tedious pretreatment and achieves a detection limit of 10 μg/L for vanillin in real tea samples. Meanwhile, this strategy is applicable to different tea systems and the detection of various aldehyde flavor molecules. Additionally, the internal standard strategy reduces systematic errors and improves the accuracy of quantitative analysis. Significance The universal Schiff base reaction-assisted SERS internal standard strategy proposed in this work can specifically capture aldehyde flavor molecules via Schiff base reaction. The developed strategy exhibits good anti-interference ability and thus expands the great potential of SERS technology in aldehyde flavor additives detection and regulatory management in food safety.