Novel magneto-electrochemical determination of Mn(II)

Abstract

This study describes the robust modification of a screen-printed carbon electrode (SPE) for the magneto-electrochemical determination of Mn2+, in real soil samples, by square wave cathodic stripping voltammetry (SW-CSV). The carbon surface of a SPE was modified with electrodeposited Au, then dropcast with Fe3O4 NPs functionalised with l-cysteine within a graphene oxide matrix. The magnetic Fe3O4 NPs within the modification significantly increased the diffusion coefficient of the paramagnetic Mn2+ ion during deposition. Likewise, it also increased the number of hydroxyls available for the formation of the MnO2 layer, attributed to chiral induced spin selectivity. The reduced graphene oxide (RGO) served to increase the surface area and heterogenous electron transfer rate of the intermediate reactions. The Au/l-cys/Fe3O4/RGO modification displayed two significant improvements: enhancement of the Mn2+ response signal (212-fold increase) and improved flexibility for the analytical method (linear ranges from 0.5 to 300 µg L-1 to 62 – 1500 µg L-1 using deposition times of 300 or 30 s, respectively). Ten soil sample extracts were tested for Mn2+, by SW-CSV using the Au/l-cys/Fe3O4/RGO modified SPE, and showed good agreement with FAAS, average error of 6.8%.