Preparation Of Paper-based SERS Substrate And Its Application In Detection Of Prohibited Pigments In Food

In recent years, food safety problems about prohibited pigment ha ve been the focus of attention. However, the existing detection methods can’t achieve efficient, rapid and accurate detection for prohibited pigment in food. Surface enhanced Raman spectroscopy(SERS) technique arises at the historic moment and it has been widely used in food, materials, medicine and other fields because of its many advantages. At the same time, the fabrication of SERS substrate with excellent performance is of great significance for the application of SERS technology in food detection field. Therefore, the preparation of SERS substrate and its application for the detection of prohibited pigment in food are of great research value.In this paper, SERS paper-based SERS substrate with good uniformity and stability as well as high sensitivity was fabricated using liquid-liquid interface self-assembly technique. In addition, based on density functional theory, the Raman spectra of several prohibited pigments were calculated by Gaussian software and the characteristic peaks were assigned to the corresponding vibration mode. Then the prohibited pigments in both simple food matrix(drinks) and complex food matrix(paprika) were detected with the prepared SERS paper-based substrate. At the same time, semi-quantitative analysis and the recovery of SERS detection were conducted, which indicated a good accuracy and reliability of the detection for prohibited pigments in food with SERS method.Firstly, Rhodamine B, sunset yellow and chrysoidine were selected as the research object, the theoretical Raman spectra were calculated and the Raman spectra of solid powder ware measured. After comparing, the positions of characteristic peaks were summarized and the corresponding vibration modes were assigned.Then, based on the interface self-assembly technology, silver nanoparticles film formed on liquid/liquid interface was deposited on the filter paper by the coating method. The fabrication process of SERS paper-based substrate is simple. The utilization rate and detection efficiency of the substrate were both improved. Furthermore, the property of the SERS paper-based substrate was investigated and discussed, indicating that this substrate has good uniformity, time stability as well as high sensitivity. It has a great application prospect in food trace detection.Next, with the prepared SERS paper-based substrate, simple samples, like drinks, were selected as food matrix. Without any pretreatment, fast and simple detection of prohibited pigment in actual drinks was achieved. Then the quantitative analysis and the detecting recovery were studied,which proves that the SERS method can be well applied in detecting prohibited pigments in drinks.Finally, selecting chili powder as complex food matrix, a simple and convenient pretreatment process for doped chili powder was developed. At the same time, the detection of Rhodamine B in chili powder and the semi-quantitative analysis were completed. The results show that SERS method in the detection of illicit pigments in complex food matrix also has great potential.