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.