Catalytic Currents ionic strength

Fig. 6 Cyclic voltammetric analysis of the kinetics of an electrode coated with antigen-antibody immobilized monomolecular layer of redox enzyme with a one-electron reversible cosubstrate in the solution, (a) Cyclic voltammetry at saturation coverage (2.6 x 10 mol cm ) of glucose oxidase with 0.1 M glucose and 0.1 mM ferrocenemethanol in a pH 8 phosphate buffer (0.1 M ionic strength). The dotted and dashed lines represent the cyclic voltammogram (0.04 V sec ) in the absence and presence of glucose (0.1 M), respectively. The full line represents the catalytic contribution to the current,/ cat (see text), (b) Primary plots obtained under the same conditions with, from top to bottom, 0.01, 0.02, 0.05, and 0.1 M glucose, (c) Secondary plot derived from the intercepts of the primary plots in (b).

Fig. 15 Variations of the catalytic plateau current in the cyclic voltammetry of ferrocene methanol in the presence of 0.5 M glucose in a phosphate buffer (pH = 8, ionic strength = 0.1 M), at 25 °C and a scan rate of 0.04 V sec at three different electrodes, (a) Electrode coated with 10 inactivated (Fg = 2.0 X 10 mol cm ) and 1 active (F° = 1.5 x 10 mol cm ) glucose oxidase monomolecular layers, (b) Electrode coated with 1-10 active glucose oxidase monomolecular layers (F = 1.5 x 10 mol cm ).

Whereas diffusion and adsorption currents are usually independent of the buffer concentration, kinetic currents (in some instances) and catalytic currents are very often a function of the concentration and composition of the buffer. The ionic strength was also observed in some instances to affect catalytic currents. 

Conversely the presence of such a catalytic wave was claimed for some substances containing no sulphur. From the study of the influence of the composition of the buffer solution, of the ionic strength and of the concentration of cobalt as well as of the concentration of the catalytically active substance, it has recently been possible to distinguish at least three different types of catalytic currents. Thus it is possible that the catalytic effects e.g. for uric acid, ) glycerinaldehyde, or dihydroxyacetone, ) have characteristics other than the catalytic waves due to thio-compounds. 

---