Non-Nernstian behaviour

This same R T state equilibrium model can also be used to interpret the non-Nernstian behaviour of Fib redox monitored by spectroelectrochemistry. Reduction or oxidation of interacting electroactive centres in Fib gives rise to a nonlinear Nernst plot. The changing slope of the Nernst plot, n, can no longer be simply interpreted as the number of electrons transferred. Nonlinear Nernstian plots obtained from such spectroelectrochemical data require a special treatment. 

Spectroelectrochemistry is a rapid and convenient method to study the redox properties of iron proteins. Nernstian behaviour can be readily identified and used to determine the formal reduction potential (Ei/2) and number of electrons ( ) involved in the oxidation/reduction process. Non-Nernstian behaviour can... 

All conditions should be as close as possible to the sample analysis. The graph E = /(log c) is utihzed as a reference to determine the concentration Cx which belongs to the measured value m- If potentiometric caUbration graphs are not linear, then a non-Nernstian behaviour is perceptible, which means that the electrode may produce inaccurate results. 

Well functioning indicator electrodes, i.e., those which show ion-selective Nernstian behaviour in non-faradaic methods, represent the ISEs. 

For the measurement of gas components like hydrocarbons (HC) or nitric oxides (NOx) in non-equilibrated gas phases kinetically determined sensors are used (Fig. 19.2 middle).Depending on the electrode material, the gas components do not equilibrate on the measuring electrode at temperatures <700 °C. Thus gas components which are not thermodynamically stable are electrochemically active. In an HC- and 02-containing gas, for example, at least two electrode reactions can take place the electrochemical reduction of oxygen and the electrochemical oxidation of hydrocarbons. The measured open-circuit voltage does not obey the Nemst equation. Therefore such electrode behaviour is often referred to non-Nernstian electrodes (or mixed potential sensors). The cell voltage depends logarithmically on the concentrations of the hydrocarbons ... 

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