Double-sampled differential square-wave voltammetry

A differential form of square-wave voltammetry (SWV) is proposed based on a double sampling current protocol within the last quarter of the duration of each potential pulse. Differential forward (I-d,I-f) and backward (I-d,I-b) current components are well defined peaks with precisely accessible peak characteristics, which is not the case in conventional variant of the technique where most frequently one encounters asymmetric or sigmoid curves. The proposed methodology is theoretically tested with a simple quasi-reversible electrode reaction of a dissolved redox couple at a macroscopic planar electrode, as well as with the mechanism where the electrode reaction is coupled with a follow-up chemical reaction (i.e. ECr mechanism). Besides expected advances in analytical context, the proposed methodology is promising for mechanistic and kinetic analysis by inspecting the features of the forward and backward current components for any degree of electrochemical reversibility. Thus, the common analysis of the net peak current in conventional SWV can be replaced with the peak current ratio of the forward-to-backward (I-p,I-f/I-p,I-b) current components in the differential variant of the technique. The peak current ratio is a dimensionless, relative parameter enabling a straightforward comparison to experimental data, which is not always the case with the net peak current of the conventional SWV.