Amperometric Detection of Cysteine at an In³⁺ Stabilized Indium Hexacyanoferrate Modified Electrode

Abstract

Abstract This research focuses on the stabilization of indium hexacyanoferrate (InHCF) modified electrode in aqueous solution and the amperometric detection of cysteine (Cys). It was found that the stability of the InHCF modified electrode in the aqueous solution could be improved upon adding In 3+ in the solution. EQCM experiments verified that such an In 3+ addition greatly inhibited an oxidized InHCF thin film's dissociation and thus considerably stabilizes the InHCF modified electrode. The amperometric detection was performed by the application of a static potential at 1.2 V, with the sampling time at 30 s. The sampled current was linearly dependent on [Cys] when [Cys] was ranged from 100 μM to 1 mM. The sampled current approached a plateau gradually with the increase in the concentration of cysteine. The trend of calibration curve at the InHCF modified electrode generally follows the Michaelis–Menten type kinetics, and K m and v max were calculated to be 3.86 mM and 30.2 μA, respectively, from the Lineweaver–Burke plot. In addition, the amperometric detection was reversible and reproducible with relative standard deviations of 2.79%.