Determination of Iron in Spinach Using Linear Sweep Voltammetry at Iodine-Coated Platinum Rotating Disk Electrode

Background: In contrast to the hyper-reactive platinum electrode, iodine-coated platinum electrode shows remarkable inertness toward adsorption and surface processes. For this reason, iodine-coated platinum electrode lends itself to interesting voltammetric applications. Hydrodynamic voltammetric analysis, one of the voltammetric techniques family, has many advantages over stationary voltammetric techniques inter alia the steady state current and the higher sensitivity. Objective: The present work is aimed at utilization of iodine-coated platinum rotating disk electrode for analysis of iron in spinach. Methods: The developed method is based on a voltammetric sweep at an iodine-coated rotating-disk platinum electrode. The optimized experimental parameters included a potential scan from -0.20 to 0.85 V versus Ag/AgCl/[Cl^-] = 1.0 M, 50 mV/s scan rate, and a rotation rate of 1000 rpm. Results: Oxidation of iron at the iodine-coated platinum rotating disk electrode was manifested by a wave at E_1/2 = +0.72 V. The limiting current was found to exhibit an excellent linearity with the concentration of iron (R₂ = 0.996). The detection limit was 0.0 7 ppm. A comparative analytical study on determination of iron content in spinach samples was conducted by the voltammetric method and ICP-OES method. Application of the paired t-test to the results indicated that the null hypothesis is valid at P = 0.05. Conclusions: A sensitive and selective validated method was developed for determination of iron content in spinach. Highlights: A simple, fast, and reliable voltammetric method was developed for iron analysis in spinach. The main feature of the developed method is removing the effect of cationic interferences.