Magnetite Nanoparticles Impregnated Carbon Paste Electrode as a New Sensing Platform for Voltammetric Determination of Citric Acid in Fruit Juice Samples

In this work, a new method was introduced for citric acid determination in real samples. The method is based on a carbon paste electrode, impregnated with magnetite nanoparticles (Fe2O3). The electrocatalytic activity of magnetite nanoparticles-modified carbon paste electrode (Fe2O3-CPE) was substantiated utilizing cyclic voltammetry (CV). Performing of CV in different pH values as well as various scan rates resulted in some evidences on the citric acid electroxidation mechanism. Electrochemical impedance spectroscopy gave obvious indication for the enhancement of charge transfer rate by the magnetite nanoparticles. Various parameters, affecting the electrode performance were studied and optimized. Square wave voltammetry (SWV) method was found to be an appropriate analytical technique to obtain enhanced electroxidation signal and thus it was adopted as the signal recording method. Using SWV and Fe2O3-CPE, a linear dynamic range of 2.5×10-5-1×10-3 mol L-1 as well as detection limit of 1 μmolL-1 was obtained for citric acid determination. Relative standard deviation percent of three repeated determinations was found to be about 4.1%. The developed method was utilized for citric acid amount estimation in different commercial fruit juices samples which led to satisfactory results.