A highly stable and sensitive chemically modified screen-printed electrode for sulfide analysis

We report here a highly stable and sensitive chemically modified screen-printed carbon electrode (CMSPE) for sulfide analysis. The CMSPE was prepared by first ion-exchanging ferricyanide into a Tosflex anion-exchang polymer and then sealing with a tetraethyl orthosilicate sol-gel,e layer. The sol-gel overlayer coating was crucial to stabilize the electron mediator (i.e., Fe(CN)(6)(3-)) from leaching. The strong interaction between the oxy-hydroxy functional group of sol-gel and the hydrophilic sites of Tosflex makes the composite highly rigid to trap the ferricyanide mediator. An obvious electrocatalytic sulfide oxidation current signal at similar to 0.20V versus Ag/AgCl in pH 7 phosphate buffer solution was observed at the CMSPE. A linear calibration plot over a wide range of 0.1 mu M to 1 mM with a slope of 5.6 nA/mu M was obtained by flow injection analysis. The detection limit (S/N = 3) was 8.9 nM (i.e., 25.6 ppt). Practical utility of the system was applied to the determination of sulfide trapped from cigarette smoke and sulfide content in hot spring water. (c) 2005 Elsevier B.V. All rights reserved.