Flow Injection Analysis of Ultratrace Sulfide at Low Potentials on Screen-Printed Carbon Electrode Modified with Cinder/Hexacyano Cobaltate Hybrid

Flow injection analysis (FIA) of ultratrace sulfide has been demonstrated on a screen-printed carbon electrode modified with industrially waste cinder/hexacyano cobaltate (CoHc) hybrid (designated as cinder/CoHcSPE) in pH 2 NH4Cl (0.1 M)/HCl solution at 0 mV (vs. Ag/AgCl). Hybridization of CoHc was achieved through bimetallic formation of FeIII[CoIII(CN)6] in the *FeIII[CoIII(CN)6] in the *Fe-enriched industrially waster cinder modifier. Possible mediated electrocatalytic oxidation of sulfide by higher oxidation state of Co in the hybrid-bimetallic complex is proposed for the system. Under the optimized conditions, the calibration plot is linear up to 2.08 μM with slope, regression coefficient, and detection limit (S/N=3) of 6.19 A/μM, 0.9985, and 12 nM, respectively. Interferences by direct electrochemical oxidation of easily oxidizable substances can be prevented due to the low detecting potential of the working system.