Novel magneto-electrochemical determination of Mn(II)

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%.