EC-SERS Spectroelectrochemical Detection of Thiabendazole Residues in Juice

The discovery of surface enhanced Raman scattering (SERS) from an electrochemical (EC)-SERS experiment is known as a historic breakthrough. Since then, great progress has been made in using this technique for various analytical purposes, Raman spectroelectrochemistry representing now a promising alternative to conventional analytical methods. By manipulating the surface charge through polarization, the physico-chemical interaction between the substrate and the target molecule can be controlled and facilitated. As a result, a higher enhancement of the Raman signal is observed. The EC modulation of substrate potentials during SERS analysis brings a series of other benefits, such as higher selectivity, possibility of preconcentration, reusability and improved reproducibility. Furthermore, the electrochemical methods for "roughening" (activation) of the low-cost screen-printed electrodes offer a convenient, accessible, and ready-to-use alternative to commercially available SERS substrates that are expensive and sometimes irreproducible. In this work we report the first EC-SERS detection of thiabendazole, a systemic fungicide used in agriculture that can be found as a contaminant in various foods, including fruit juices. The EC-SERS measurements were performed using a portable Raman spectrometer and a potentiostat. Commercially available gold screen-printed electrodes were used after an optimized electrochemical activation procedure. An applied potential to the substrate (-0.8V vs. Ag/AgCl) further increases the SERS signal of thiabendazole allowing its detection down to 0.06 ppm (0.3 μM), with a relatively wide linear range (0.5 - 10 μM) and good intermediate precision (RSD%