It is well known that for this system the kinetic parameters reported are highly variable even when using apparently identical electrodes and conditions (see and references cited therein). Using our new approach we are able to show that this difficulty is not due to the impact of random experimental noise, since for each individual data set we are able to fit the mathematical model to the experimental data extremely accurately. However, we are able to demonstrate that the recovered values from each individual data set vary significantly from one another, i.e. the system itself varies between experimental runs, and so the recovered parameter values are extremely sensitive to the precise experimental conditions pertaining on that particular run. Since we have already demonstrated its advantages over the dc approach, we restrict ourselves to the ac case in this paper.