Chronopotentiometric/chronoamperometric transient analysis of naproxen via electrochemically synthesized nano spinel ZnFe2O4 films

Abstract

Nano spinel zinc ferrite films (ZFO) are synthesized by peroxide assisted electrochemical oxidation and used as functional anodic material to detect naproxen under chronopotemtiometric and chronoamperometric mode. Electrochemical characterization, texture, morphology and lattice structure of the films were explored. Electrochemical kinetics of oxy hydroxide deposition as well as anodic oxidation was evaluated and it follows quasi-reversible type. Formation of Zn2+ rich ferrite phase was impeded by mass-transfer rate, whereas Fe2+ oxy hydroxides formation was lowered in the initial stages by charge-transfer rate, with the diffusion coefficient of 6.44 × 10−8 cm2 s−1 and has an exchange current density of 0.83 A dm−2. In IR spectra, tetrahedral ZnO (463 cm−1) and octahedral FeO stretching (630 cm−1) vibrations are distinct. Based on X-ray diffraction data lattice parameters and d-spacing were explored with indigenously designed computer simulation program, ‘Crystalsim’. From electronic configurations and geometric correlations, it was observed that, tetrahedral sites are occupied by Zn2+ and octahedral sites are occupied by Fe3+ ions and thus forms normal cubic spinel and the O2– form fcc lattice. Anodic oxidation of naproxen involves predominantly one electron transfer through the formation of 2-methoxy-6-ethylnaphthalene carbanion by surface adsorptive decarboxylation followed by formation of peroxide compound. Thermodynamic parameters were estimated and the rate constant and free energy are 2.49 × 10−9 s−1 and −49.91 kJ mol−1 respectively. Surface coverage concentration of anions was about 3.45 × 10−10 mol cm−2 at 1.00 × 10−4 M and charge-transfer restriction lowers the coverage rate and 4.03 × 10−4 mM of anion was undergone for oxidative e- transfer under an applied potential of 0.55 V at 300 s. By ANOVA techniques, Limit of Detection and Limit of Quantitation were assessed and are about 1.30 × 10−5 M and 4.10 × 10−5 M respectively. Using non-linear interpolation models and from higher order polynomials, quantification of naproxenate ion can be achieved with better precision from the oxidation charge at the applied anodic potential. From electrochemical impedance studies, it can be shown that ZFO has substantial electrocatalytic activity towards the oxidation of naproxenate anion. The Nyquist charge-transfer resistance of the modified ZFO after adsorption and oxidation of the naproxenate anions is increased (2928 Ω) significantly when compared with unmodified ZFO (509 Ω). Since potentials are discrete in presence of interfering ions, such as ibuprofen, salicylate diion and Cl− and the respective selectivity coefficients were estimated by mixed two-solution method. It is about 1.9843 and 0.3509 at 1.0 × 10−4 M for ibuprofen and methyl salicylate respectively. As electrochemical synthesis of ZFO is relatively cost-effective and the fabricated films can be deployed as a viable functional anodic material for electrochemical detection of naproxen by chronopotentiometric/chronoamperometric techniques.