Constant-potential amperometric detection of underivatized amino acids and peptides at a copper electrode

Development of instrumentation for amperometric and coulometric detection using ultramicroelectrodes

“…The CV obtained for Cu UME (Figure 3(a)) was fully in accord with what has previously been reported for copper electrodes exhibiting anodic waves at -0.36 and +0.05 V, corresponding to the formation of Cu (I) and Cu(II) oxides, respectively, and related cathodic waves at -0.55 and -0.81 V, representing the reductions to Cu(I) and Cu(0). 6,18,19 The CV for Ni UME (Figure 3(b)) presented two well-defined anodic and cathodic peaks at +0.48 and +0.42 V. The redox couple is associated to the oxidation of Ni(II)(OH) 2 to Ni(III)O(OH) and its reduction to Ni(II)(OH) 2 .…”

“…The constant potential detection of most aliphatic compounds has been achieved by oxidation at non-noble electrode such as Cu, Ni and Co. 3,6,7 These metals can catalyze the electrode oxidation process through the formation of species of Cu(III), Ni(III) and Co(III) which are commonly believed to act as a redox mediators between substrate and electrode. The alkaline medium (pH >13) represents the main requirement to form and stabilize the catalytic species on the electrode surface.…”

“…On the other hand, unlike the glassy carbon electrode, the non-noble metal electrodes, such the Cu, Ni, and Co electrodes, can catalyze the oxidation process of polar aliphatic compounds through the formation of species of Cu(III), Ni(III) and Co(III) which are commonly believed to act as a redox mediators between substrate and electrode. 4,6,7 In noble metal electrodes, the existence of partial filled d-orbital promotes stabilization of free radicals and compounds with nonbonded electrons pair by adsorption at electrode surface. Unfortunately, this beneficial effect of adsorption (i.e., electrocatalytic activity) is accompanied by the undesirable tendency of the electrode surface to become fouled by the accumulation of adsorbed compounds.…”

“…The CV obtained for Cu UME (Figure 3(a)) was fully in accord with what has previously been reported for copper electrodes exhibiting anodic waves at -0.36 and +0.05 V, corresponding to the formation of Cu (I) and Cu(II) oxides, respectively, and related cathodic waves at -0.55 and -0.81 V, representing the reductions to Cu(I) and Cu(0). 6,18,19 The CV for Ni UME (Figure 3(b)) presented two well-defined anodic and cathodic peaks at +0.48 and +0.42 V. The redox couple is associated to the oxidation of Ni(II)(OH) 2 to Ni(III)O(OH) and its reduction to Ni(II)(OH) 2 .20,21 A characteristic electrochemical behavior of Co was obtained, as can be observed in Figure 3(c). 4,22 The CV for Au UME (Figure 3(d)) presented two waves, which were related to the oxide formation (AuOH and AuO) and the reduction of the surface oxide at +0.460 and +0.100 V, respectively.…”

Bioanalytical profile of the l-arginine/nitric oxide pathway and its evaluation by capillary electrophoresis

“…Microchipintegrated CEECD has been developed and tested with biomedical samples, showing excellent analytical performance and good technological potential for microfabrication [335]. The effort to develop CEECD applications focuses on the analysis of neurochemically and metabolically important small biogenic and essential molecules, including amino acids [336][337][338][339][340][341][342], monoamines [343][344][345][346][347][348][349][350][351][352], excitatory and inhibitory neurotransmitters with low electrochemical activity [342,353], and some vitamins and cofactors such as ascorbic acid and glutathione [354][355][356][357][358][359][360][361][362][363][364].…”