Electrocatalytic behaviour of hybrid cobalt–manganese hexacyanoferrate film on glassy carbon electrode

• A hybrid cobalt–manganese hexacyanoferrate film was prepared.
• The hybrid film possesses excellent charge transfer properties.
• The hybrid film exhibits excellent electrocatalytic properties towards Tryptophan.
• Tryptophan detection is possible from commercial milk samples.

A thin film of hybrid cobalt–manganese hexacyanoferrate (CoMnHCF), a redox mediator was electrodeposited on a glassy carbon (GC) electrode and was employed as an amperometric sensor towards l-Tryptophan (l-Trp). The hybrid film was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction technique (XRD), scanning electron microscope–energy dispersive X-ray spectroscopy (SEM–EDAX), and electrochemical techniques. The atomic absorption spectroscopic analysis provided the stoichiometry of the hybrid film to be K1.74-y Coy Mn0.78 [Fe(CN)6], y ≤ 0.68. The electrochemical impedance study revealed the excellent charge transfer properties of GC/CoMnHCF electrode. The voltammetric investigations demonstrated exceptional electrocatalytic properties of the hybrid film modified electrode when compared to that of bare GC, GC/CoHCF and GC/MnHCF electrodes, towards the l-Trp oxidation. The kinetic parameters such as electron transfer coefficient, the electron transfer rate constant, the diffusion coefficient and the catalytic rate constant for the electrooxidation process of l-Trp were investigated. The amperometric detection of l-Trp employing GC/CoMnHCF electrode possessed a good sensitivity of 10 × 10− 2 A M− 1 cm− 2 in a wide range of detection (2–200 μM) at a reduced overpotential of 680 mV. In addition, the proposed amperometric method was applied to the detection of l-Trp in commercial milk samples with reproducible results.