Stamplike flexible SERS substrate for in-situ rapid detection of thiram residues in fruits and vegetables

A simple and sensitive Surface-Enhanced Raman Spectroscopy (SERS) method for the detection of thiram residues in fruit and vegetable peels is reported. A flexible SERS substrate based on silver nanoparticles in an agar gel has been developed and characterised. Peels of different fruits and vegetables were intentionally contaminated with different amounts of thiram. The analyte was then extracted within few seconds by gentle rubbing the surface with the agar substrate using it as a stamp. The optimum experimental conditions of the developed method were explored. The limit of detection of thiram in the peels of tomato and green pepper was 140 pg/cm2. The values achieved for apple was 2 pg/cm2. The method presented could be extensively used for the detection of traces of other contaminants on food surfaces and for other relevant applications.