Electrochemical studies and sensing of iodate, periodate and sulphite ions at carbon nanotubes/ prussian blue film modified platinum electrode

This work describes the modification of platinum electrode with and without functionalised multi-walled carbon nanotubes (MWCNT-SO₃^2-) and prussian blue nanoparticles (PB) for the detection of iodate, periodate and sulphite ions. The modified electrodes were characterised using techniques such as transmission electron microscopy (TEM), electron dispersive X-ray spectroscopy (EDX), cyclic voltammetry (CVs) and electrochemical impedance spectroscopy (EIS). The Pt-MWCNT-PB electrode exhibited enhanced electron transport and catalytic efficiency towards the electrocatalysis of iodate (IO₃^-), periodate (IO₄^-) and sulphite (SO₃^2-) compared to the other electrodes studied. The electrode was characterised by some level of adsorption due to adsorbed intermediates. The degree of adsorption was quantified as indicated by the Tafel values of 211.0, 176.2, and 129.2 mVdec^-1 for iodate, periodate and sulphite respectively. The analytes were detected at micromolar level. The limit of detection and the catalytic rate constant were 8.30 μM (1.37x10⁶ cm³mol^-1s^-1), 8.06 μM (0.34x10⁶ cm3mol^-1s^-1) and 4.70 μM (5.24 x 10⁷ cm3mol^-1s^-1) for iodate, periodate and sulphite. The electrode detects iodate in the presence of the interfering effect from other oxo-anions. This electrode can be reliably used to assay iodate in real or commercial salt composition.