Determination of diffusion coefficients from semiintegrated d.c. and a.c. voltammetric data: Overcoming the edge effect at macrodisc electrodes

• D.c. and a.c. voltammetric edge current causes the semiintegral plateau to slope.
• Diffusivity can be derived from the sloping semiintegral via several methods.
• The most successful method based on iterated convolutions is complicated.
• Simpler and almost as effective is the constrained linear regression method.
• Less successful, but simple, are straightforward extrapolation methods.

Unless the area of an inlaid disc electrode is sufficiently large, and/or the scan rate fast enough, the ‘plateau’ of a semiintegrated d.c. voltammogram or aperiodic component of an a.c. voltammogram has a slope. This phenomenon, which has its origin in non-planar diffusion at the edge of the disc, interferes with an otherwise efficient method of determining diffusion coefficients. Methods of circumventing this difficulty are presented and tested with simulated and experimental data.