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

. [Display omitted] ► 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 Fe II/Fe III 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. A novel copper hexacyanoferrate (CuHCF) film modification on cysteamine (Cys)-gold nanoparticle (AuNp) graphite-wax (GW) composite electrode was achieved for the quantitative determination of L-Tryptophan (L-Trp) at a reduced overpotential of 400 mV in comparison with the bare Cys-AuNp-GW composite electrode. This modified electrode exhibited a well resolved pair of redox peaks corresponding to the hexacyanoferrate (II/III) reactions of CuHCF film at a formal potential of 0.65 V at a scan rate of 20 mV s −1. Electrochemical impedance spectroscopy (EIS) studies with the modified electrode showed a very low charge transfer resistance to the electron transfer kinetics of Fe II/Fe III reactions. A linear range of 8.5 × 10 −7 M to 1.2 × 10 −4 M with a detection limit of 1.85 × 10 −8 M was achieved for the determination of L-Trp with a sensitivity of 0.1198 μA/μM. The influence of ultrasonication on the stability of the CuHCF film modified electrode was investigated. In addition, the CuHCF film modified electrode displayed an excellent reproducibility towards the real time analysis of l-Trp in commercial milk samples.