Glassy carbon catechols

The conditions for reliable cyclic voltametry determination of trace Sn concentrations in sea water were investigated. All organotin compounds should be converted to Sn(II) by UV-photolysis adsorption on mercury drop in the presence of 40 pM of tropolone (1) cyclic voltametry stripping shows two cathodic peaks, corresponding to the two-step process Sn(IV) — Sn(II) -> Sn(0)29. A complex of Sn ions with catechol can be accumulated in a glassy carbon mercury film electrode, followed by stripping voltametry measurement in the cathodic direction, at pH 4.2-4.7. Interference occurs when Cu, Cd and Cr are present LOD 0.5 pg/L for 300 s accumulation30. 

The combination of anodic oxidation of benzene using the Ag(I)/Ag(II) mediator with cathodic oxidation of benzene using the Cu(I)/Cu(II) mediator in a single electrolytic cell produces p-benzoquinone selectively in both the anodic and the cathodic chambers [242]. Silver-mediator promoted electrooxidation of hydrocarbon has been attempted [243]. The kinetics of indirect oxidation of catechol and L-dopa with IrCl6 has been studied in polymer-coated glassy carbon [244]. 

The choice of working electrode material is an important factor in amperometric detection. For catechols and similar substances, such as phenolic acids, electrodes made of glassy carbon have shown good performances. Other good detectable and biological important substances include thiols and disulfides (e.g., cysteine, glutathione, and their disulfides which... 

ZnO nanoparticles dispersed CH composite films deposited onto glassy carbon electrode (GCE) have been used for immobilization of tyrosinase enzyme for phenol detection. This biosensor shows 95% of steady-state current within 10s, sensitivity as 182 pA mmol"1 L with a detection limit of 5.0 x 10"8 mol/L, exhibits maximum response at 50°C and retains 91% current after about 20 days [39], A sol-gel derived ZnO matrix has been used to immobilize tyrosinase for determination of phenol concentration from 1.5 x 10"7 to 4.0 x 10"5 mol L"1 with detection limit of 8.0 x 10 s mol L"1 and sensitivity of 168 pA mmol L"1. This biosensor shows 95% of steady-state current within 15s after 2 weeks [40], Chen et al. have immobilized mushroom tyrosinase oxidase onto ZnO nanorods for the phenol and catechol detection. The linear concentration ranges have been obtained from 0.02 to 0.1 mM and 0.01 to 0.4 mM, for phenol and catechol, respectively. The apparent Km has been estimated as 0.24 mM for phenol and 1.75 mM for catechol [59],... 

DuVall. S.. and McCreery, R.L. 1999. Control of catechol and hydroquinone electron transfer kinetics on native and modified glassy carbon electrodes. Analytical Chemistry 71, 45594-45602. 

Phenols / -bromophenol, catechol, p-chlorophenol, hydroquinone, o-nitrophenol, p-nitrophenol, phenol and resorcinol C8 amperometry with glassy carbon electrode gradient elution solvent A (0.05 M SDS-3% 1-propanol-phosphate buffer at pH 2.5-NaC104 added to balance the conductivity) to solvent B (0.112 M SDS-3% 1-propanol-phosphate buffer at pH 2.5) in 15 min. 17... 

Molecular Adsorption Studies of Catechols at Diamond and Glassy Carbon Electrodes (pmol/cm )... 

This move from the modification of electrodes to the modification of nonconducting surfaces in contact with electrodes is also seen in systems in which electrodes are modified using nonconduct ive particles. For example, Zak and Kuwana showed that the basic surface of alpha-alumina imbedded in glassy carbon electrodes caused catalysis of the electrooxidation of catechol and other organic species requiring loss of a proton for their oxidation JJ ), Similar results were obtained by Shaw and Creasy (78) using alumina or layered-double hydroxides in composite electrodes (vide infra). 

The surface properties of other solids also have potential applications. For example, electro-oxidation of catechol was catalyzed on a layered double hydroxide, Zn Aly (OH" )2x+3y-z (Cl )2 which has a basic surface (78), Similar behavior was observed on alumina-modified glassy carbon as described above (77). Voltammetric data suggest that catechol and related hydroxy compounds adsorb to the surface of these basic solids. Charge transfer may occur across the surface of the solid among adsorbed electroactive sites. If heterogeneous electrocatalysis at the surfaces of nonconducting solids turns out to be general, the possibilities in electroanalytical and electrosynthetic applications are endless. 

Nagoka and Yoshino (1986) studied the surface properties of electrochemically pre-treated glassy carbon by cyclic voltammetry and adsorption of catechol (1,2-dihydroxybenzene). The authors concluded that adsorption of quinones (on glassy carbon and pyrolytic graphite) depends on an electronic effect such as an electrostatic attraction between the adsorbate and partial surface charges, rather than a specific chemical effect. 

Liu, A. and E. Wang. 1994. Determination of catechol derivatives on pretreated and copolymer coated glassy carbon electrode. Talanta 41 147-154. 

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