Electrocatalytic oxidation of l-tryptophan using copper hexacyanoferrate film modified gold nanoparticle graphite-wax electrode

► A novel copper hexacyanoferrate (CuHCF) film modification on cysteamine (Cys)-gold nanoparticle (AuNp) graphite paraffin wax (GW) composite surface was developed. ► A successful quantitative determination of l-Tryptophan (l-Trp) was achieved at a reduced overpotential of 400 mV in comparison with the bare Cys-AuNp-GW composite electrode surface. ► Electrochemical impedance spectroscopy (EIS) studies with the modified electrode showed a very low charge transfer resistance to the electron transfer kinetics of FeII/FeIII reactions. ► A linear range of 8.5 × 10−7 M to 1.2 × 10−4 M and with a detection limit of 1.85 × 10−8 M was achieved for the determination of l-Trp with a sensitivity of 0.1197 μA/μM. ► The CuHCF film modified electrode displayed an excellent reproducibility towards the real time analysis of l-Trp in commercial milk samples.