Indirect Differential Pulse Voltammetric Determination of Fluoride Ions at Carbon Paste Electrode Modified with Porous and Electroactive Fe3+/Fe2+ Based-Metal Organic Frameworks Type MIL-101(Fe)

Abstract

An innovative and reliable electrochemical sensor was proposed for simple, sensitive and selective determination of F− ions. The sensor based on the fabrication of porous and electroactive Fe-based metal organic frameworks [MIL-101(Fe)]. It was blended with graphite powder and liquid paraffin oil to from carbon paste electrode (CPE). The MIL-101(Fe)@CPE was characterized using different techniques such as scanning electron microscope, powder X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray, cyclic voltammetry, electrochemical impedance spectroscopy, differential pulse voltammetry. The MIL-101(Fe)@CPE exhibited two redox peaks (anodic and cathodic) corresponding to Fe3+ and Fe2+, respectively. The determination of F− ions based on the formation of a stable fluoroferric complex with Fe3+/ Fe2+, decreasing the currents of redox species. It was found that the anodic peak current (Ipa) is linearly proportional to the concentration of F− in the range of 0.67–130 μM with a limit of detection (S/N = 3) of 0.201 μM. The electrode exhibited good selectivity towards F- detection with no significant interferences from common anions. The as-fabricated sensor was applied for the determination of F− in environmental water samples with recoveries % and RSDs % in the range of 98.1%–102.4% and 2.4%–3.7%, respectively.