When you try to fit catalytic waves, don't take a crap fit for granted: this could happen because the initial values of the reduction potentials are too far from the mid-wave potential. When you try to fit overlapping non catalytic peaks, try to keep to a minimum the number of adjustable parameters.
In the case of a two-electron non-catalytic signal (ncli), the peak shape is insensitive to DeltaE=E(O/I)-E(I/R) if DeltaE is too negative (when the one-electron reduction potentials are too crossed), say lower than -50mV. In this case, ET is cooperative, the peak looks like a two-electron peak and the best values of E(O/I) and E(I/R) are meaningless: only the average two-electron reduction potential E(O/R)=(E(O/I)+E(I/R))/2 can be interpreted. If the 2-electron peak looks very much like a cooperative 2-electron peak, ncai should be used, fixing napp to 2.
In the case of catalytic wave shapes, if the one-electron reduction potentials are found to be crossed, the same remark as above applies. If on the contrary E(O/I) is `much' greater than E(I/R), the signal is essentially a one-electron wave, and the oxidative or reductive waveshape is insensitive to E(I/R) or E(O/I) respectively. To check whether that is the case, you should make sure that no reduction potential lies in the electrode potential range where there is no current (in the baseline before the onset of activity). Another thing to do if you're not sure is to fit the oxidative or reductive wave again, FIXING E(I/R) or E(O/I) (respectively) to a very low or high value (respectively). If the fit is not significantly worse than when you adjust both reduction potentials, that means that the wave is a one-electron wave, and that only E(O/I) or E(I/R) (respectively) can be measured. This is discussed in the appendix of .
Christophe Leger 2009-02-24