Data from overlapping signals at an amperometric electrode using admittance vectors

A simple admittance vector presentation, common in telecommunication signal processing, is examined to separate mathematically two overlapping analytical amperometric signals. The method is based on a theoretical derivation of a constant potential amperometric electrochemical system experiencing an ac perturbation. For a given reaction at different concentrations of the electrochemically active species, the current measured during an ac perturbation at a particular frequency on a constant bias potential Edc, has constant phase angle (φ) of the admittance and only its magnitude (Y) changes with concentration. The complex admittance vector space is spanned by the basis vectors of the individual components of a mixture. The admittance measurement is thus given in terms of the contribution from these components. The concentration calibration may be computed by taking the distance to each admittance point. In the context of the conventional constant potential amperometric methods for detection of H2O2 and ascorbic acid via their oxidation currents, where there is an inherent problem of interference and overlap of each electroactive species, their simultaneous estimation is taken as a model case to illustrate the methodology to extract the basis vectors for each species and obtain the concentration calibration vectors for the mixture. Evaluation of the use of the technique in complex mixtures is introduced.