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Nickel pentacyanonitrosylferrate (NiPCNF) films have been deposited on the surface of aluminum substrate by a simple electroless dipping method. The cyclic voltammogram of the resulting surface modified Al electrode prepared under optimum conditions, shows a well-behaved redox couple due to the [NiIIFeIII/II(CN)5NO]0/–1 system. The NiPCNF films formed on the Al electrode show electrocatalytic activity towards the oxidation of thiosulfate in sodium nitrate solution. A linear calibration plot is obtained over the thiosulfate concentration range 5–110 mM and 0.001–100 mM, using linear sweep voltammetry and hydrodynamic voltammetry (at a fixed potential and stirred solutions), respectively. The kinetics of the catalytic reaction were investigated using cyclic voltammetry, rotating disk electrode (RDE) voltammetry and chronoamperometry. The results were explained using the theory of electrocatalytic reactions at chemically modified electrodes. The average value of the rate constant for the catalytic reaction evaluated by the three different approaches, is 9×10−3 cm s−1. Further examinations of the modified electrodes show that the modifying layers (NiPCNF) on the aluminum substrate show reproducible behavior and a high level of stability.

The use of aluminum substrate as an electrode and the modification of its surface by means of the thin film of nickel pentacyanonitrosylferrate (NiPCNF) was developed. The modification conditions of aluminum surface including the electroless deposition of metallic nickel on the electrode surface from NiCl2+NH4Cl solution and chemical derivatization of deposited nickel to NiPCNF film in solution of 10 mM sodium pentacyanonitrosylferrate (PCNF)+0.5 M NaNO3+0.03 M HNO3 are described. The modified Al electrode prepared under optimum conditions, shows a well-defined redox couple due to [NiIIFeIII/II(CN)5NO]0/–1 system. The effect of pH and radius of the hydrated alkali-metal cation of supporting electrolyte on the electrochemical characteristics of the modified electrode were studied in detail. Diffusion coefficients of alkali-metal cations in the film (D),transfer rate constant for electron (ks) and transfer coefficient (α) were calculated. The electrocatalytic activity of the modified electrode on the oxidation of hydrogen peroxide and ascorbic acid was demonstrated as a typical example of applications.

Nickel hexacyanoferrate (NiHCNF) film modified Al electrode prepared by simple and rapid electroless dipping procedure was used for the mediated oxidation of ascorbic acid. The anodic peak current observed in cyclic or linear sweep voltammetry was linearly dependent on the ascorbic acid concentration. At a fixed potential under hydrodynamic conditions (stirred solutions), the calibration plot was linear over the ascorbic acid concentration range 2×10−6–2×10−4 M. The detection limit of the method is 2×10−6 M, low enough for trace ascorbic acid determination in various real samples. The proposed method was used for determination of ascorbic acid in fresh fruit juices, vegetables, pharmaceutical preparations and blood plasma. The results obtained are in good agreement with those obtained by the official standard methods. The analysis with NiHCF-film-modified Al electrode was selective for ascorbic acid from the various concomitant reducing compounds in real samples.