Performance of an Enzyme Electrode Designed for a Sulfide Monitoring Biosensor

The construction and evaluation of an enzyme electrode designed for a sulfide monitoring biosensor, are reported in this work. The enzyme, which is immobilized in a carbon (graphite) paste with 1,1′ dimethylferrocene, catalyzes the oxidation of sulfide to sulfur. Amperometric measurements were carried out at room temperature, and a fixed potential of 0.3 V with reference to a saturated calomel electrode, using Tris-HCl buffer (pH 7.5) as the electrolyte, and sodium sulfide solution as the substrate. Under deaerated conditions, the biosensor responded linearly to the tested sulfide concentration range of 0–4mM, giving an average apparent Michaelis constant of 3mM, and maximum current responses between 0.7 and 3.6 μA. The sensitivity of the electrodes tested ranged from 0.2–0.3 μA mM−1.