Thin functionalized films on cylindrical microelectrodes for electrochemical determination of Hg(II)

Cylindrical carbon fiber microelectrodes (CFMEs) were used for the determination of Hg(II) in aquatic solutions using anodic stripping voltammetry (ASV). Optimizing the parameters, such as the potential and time of deposition, resulted in linear response of the fiber over a large range of Hg(II) concentrations (5 × 10^-8-1 × 10^-5 M). Furthermore, three methods of modification of glassy carbon and CFMEs with thiol or other Hg(II)-complexing groups, have also been examined. Electrodes were modified by electrochemically reducing 4,4′- disulfanediyldibenzenediazonium, followed by reduction of the disulfide bond, by electrodepositing sol-gel based on 3-mercaptopropyltrimethoxysilane and by spin-coating or adsorbing cellulose acetate thin films in which 4,13-didecyl-1,7,10,16-tetraoxa-4,13-diazacyclooctadecane (Kryptofix® 22DD) was incorporated. We found that all modified glassy carbon electrodes extracted Hg(II) under open-circuit potential, however, only the cylindrical microelectrode modified via the electrochemical reduction of the diazonium was capable of extracting mercuric ions. The interference of Pb(II), Cd(II), and Cu(II) with the determination of Hg(II) with 4,4′- disulfanediyldibenzenediazonium modified CFME was also studied.