A glassy carbon electrode modified with hollow cubic cuprous oxide for voltammetric sensing of L-cysteine

This paper reports on an electrochemical sensing system for L-cysteine. It is based on the use of hollow cubic Cu₂O particles that were prepared in two steps. First, the Cu₂O/ polystyrene (PS) composites were prepared by a surface ion exchange strategy for in-situ reductive deposition on the surface of carboxy-capped PS particles. Thereafter, the PS particles were removed from the Cu₂O/PS composites by treatment with tetrahydrofuran (THF). The resulting hollow cubic Cu₂O particles were placed in a Nafion matrix on a glassy carbon electrode (GCE) which exhibits high surface area, good site accessibility and excellent electrocatalytic activity for L-cysteine. The cyclic voltammetric response of the modified GCE to L-cysteine is about 2.8-fold stronger than when using a GCE modified with pure Cu₂O. The detection limit for L-cysteine is lower by about 1 order of magnitude, and the working voltage is rather low (-0.08 V vs. Ag/AgCl). An excellent electrochemical selectivity for L-cysteine over other amino acids was also achieved. The method was successfully applied to the determination of L-cysteine in pharmaceutical samples. Graphical abstract An electrochemical sensing system for the detection of L-cysteine in amino acid injections has been established by using the hollow cubic Cu₂O particles as recognition element.