Application of MWCNTs/Fe3O4 modified electrode under inducing adsorption for rapid and sensitive detection of cadmium in a lab-on-valve system

Abstract

A rapid and sensitive approach for the determination of trace levels of cadmium using stripping voltammetry coupled with a sequential injection lab-on-valve system was developed. The proposed method was based on the accumulation of cadmium on the multi-walled carbon nanotubes/Fe₃O₄ nanoparticles modified electrode where iodide was used as the induced adsorption media. Different parameters such as supporting electrolyte and its pH, concentration of KI, amounts of modifier, accumulation potential, accumulation time, and flow rate were investigated to enhance the analytical performance. Under the optimum conditions, the signal intensity shows a linear relationship with the concentration of cadmium over the range of 5 × 10⁻⁹ to 2 × 10⁻⁷ mol L⁻¹. A sampling frequency of 24 per hour and a detection limit of 2.7 × 10⁻⁹ mol L⁻¹ were obtained with an accumulation time of 120 s. The relative standard deviation for 11 repeated measurements of 1 × 10⁻⁸ mol L⁻¹ cadmium was 3.2%. The analytical use of the established method was validated by applying it to the determination of cadmium in natural waters samples and certified reference materials.