Direct electrooxidation of artificial sweetener sucralose on Cu/Cuo modified electrodes

An enzyme-free electrochemical method for quantitatively sensing the artificial sweetener sucralose is described in this manuscript. The method relies on using a copper/copper oxide (Cu/CuO) modified screen-printed carbon electrode (SPCE) and a Cu/CuO modified platinum (Pt) wire electrode for direct electrochemical oxidation of sucralose. Morphological characterization revealed that electrodeposition resulted in spherical Cu/CuO mesoclusters on both electrode surfaces. In an electrolyte containing 0.1 M NaOH, the Cu/CuO-SPCE electrode detected sucralose concentrations up to 20 mM, while the Cu/CuO–Pt wire electrode responded up to 75 mM. Both platforms showed fast detection, with response times under 5 s. Mechanistic studies indicate that in the presence of a stoichiometric amount of 1 M NaOH, sucralose initially undergoes intramolecular SN 2 cyclization. This occurred between C9 primary hydroxyl group and the C12 primary chloride on the fructose ring, forming a crystalline tricyclic product. With three equivalents of 1 M NaOH, the fructose unit undergoes a double SN 2 process to produce a stable tetracyclic compound. The tricyclic structure was confirmed by X-ray crystallography, and both cyclized products were characterized by 1 H and 13 C NMR spectroscopy. The tricyclic assignment was based on 1D and 2D NMR analyses. Unlike its strong stability under acidic conditions, sucralose is unstable and undergoes intramolecular SN 2 cyclization in basic media.