HPTLC-FLD-SERS as a facile and reliable screening tool: Exemplarily shown with tyramine in cheese

Liao Wang ^a,b,c, Xue-Ming Xu ^a,b,c, Yi-Sheng Chen ^a,b,c,*, Jie Ren ^d,Yun-Tao Liu ^e

^a State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China

^b School of Food Science and Technology, Jiangnan University, Wuxi 214122, China

^c Collaborative Innovation Center of Food Safety and Quality Control in Jiangsu Province, Jiangnan University, Wuxi 214122, China

^d Nanchong Food and Drug Administration, Nanchong 637100, China

^e College of Food Science, Sichuan Agricultural University, Yaan 625014, China

The serious cytotoxicity of tyramine attracted marked attention as it induced necrosis of human intestinal cells. This paper presented a novel and facile high performance thin-layer chromatography (HPTLC) method tailored for screening tyramine in cheese. Separation was performed on glass backed silica gel plates, using methanol/ethyl acetate/ammonia (6/4/1 v/v/v) as the mobile phase. Special efforts were focused on optimizing conditions (substrate preparation, laser wavelength, salt types and concentrations) of surface enhanced Raman spectroscopy (SERS) measurements directly on plates after derivatization, which enabled molecule-specific identification of targeted bands. In parallel, fluorescent densitometry (FLD) scanning at 380</400 nm offered satisfactory quantitative performances (LOD 9 ng/zone, LOQ 17 ng/zone, linearity 0.9996 and %RSD 6.7). Including a quick extraction/cleanup step, the established method was successfully validated with different cheese samples, both qualitatively (straightforward confirmation) and quantitatively (recovery rates from 83.7 to 108.5%). Beyond this application, HPTLC-FLD-SERS provided a new horizon in fast and reliable screening of sophisticated samples like food and herb drugs, striking an excellent balance between specificity, sensitivity and simplicity.