Voltammetric determination of caffeic acid by using a glassy carbon electrode modified with a chitosan-protected nanohybrid composed of carbon black and reduced graphene oxide

Differential pulse voltammetry (DPV) was employed for the determination of caffeic acid (CA) in acidic solutions by using a glassy carbon electrode (GCE) modified with a chitosan-protected nanohybrid composed of carbon black and reduced graphene oxide. Electrochemical impedance spectroscopy and cyclic voltammetry were utilized to study the interfacial electron transfer on the modified GCE. Cyclic voltammetry shows that CA exhibits a reversible redox reaction with an oxidation peak at + 0.30 V (vs. Ag/AgCl) and a reduction peak at + 0.24 V in pH 3.0 solution at a scan rate of 50 mV·s−1. Under the optimized experimental conditions, the response to CA is linear in 0.3× 10−9 to 57.3 × 10−5 M concentration range. The limit of detection is 0.03 × 10−9 M (at an S/N ratio of 3), and the electrochemical sensitivity is 5.96 μA∙ μM−1∙cm−2. This sensor for CA displays better sensitivity and a response over a wider concentration range. It was applied to the determination of CA at trace levels in various (spiked) wine samples. [Figure not available: see fulltext.]