Novel ultrasensitive and ultrafast voltammetric determination of biological aminochromes on the copper nanodoped mercury monolayer carbon fiber electrode

Fast cyclic voltammetry of redox system NAD+/NADH on the copper nanodoped mercury monolayer carbon fiber electrode

“…As a result, the electrocatalytic process of systems where Cu 2+ acts as a catalyst on a nanostructured Cu-MMCFE ( Fig. 1) occurs very fast (diffusionless conditions) which assures a picomolar sensitivity for Cu 2+ determination [10] as well as for the biosystems whose redox transformation are catalyzed by Cu 2+ [8,9] under conditions where fast cyclic voltammetry is applied.…”

“…2, curve a) is registered at nanomolar range of NADH for a potential scan rate exceeding 100 V s À1 . The nanomolar sensitivity of NADH detection presumably occurs due to adsorption on the electrode of dissolved coenzyme through it complexation [14,15] with adsorbed Cu 2+ (anion-induced [9]) (reaction (6)). …”

“…If this hypothesis is correct then the addition of a protolytic active compound, able to adsorb specifically on mercury layer, must increase the electrocatalytic signal of NADH while contributing to the registration of a linear CC. Taking into account that the mechanism of redox transformation of aminochromes and of NAD + /NADH is similar (reactions (2) and (3)) and that the bovine serum albumin (BSA) increases by a few orders the voltammetric sensitivity of aminochromes [9] we have selected this protein as a protolytic agent.…”

“…This parameter (sensitivity) can serve implicitly as a measure of catalytic efficiency of chemical reactions (9)- (11) in the considered redox process. The variation of the experimental time window also could be useful in an eventual attempt to quantify separately the coenzyme mixture components taking into account that chemical reaction (9) in contrast to reaction (11) could contribute to an additional (to electrolytic) deposition of copper atoms [13] and that the MMCFE is extremely sensitive to these atoms [10].…”

“…Recently [8,9] we have demonstrated that the mercury monolayer carbon fiber electrode doped with the atoms of metallic copper (Cu-MMCFE) is a powerful agent for recycling of biologically important redox systems accompanied by hydrogen (proton) transfer (reaction (3)) due to generation of highly chemically active hydrogen intermediates -H 0 (atomary hydrogen, a strong reductant) and H þ 2 (the molecular ion, a strong oxidant) under conditions where fast voltammetry (v (potential scan rate) > 100 V s À1 ) is utilized.…”