Effects of restricted diffusion at ultramicroelectrodes in brain tissue: The pool model: theory and experiment for chronoamperometry

• Published in: Journal of electroanalytical chemistry and interfacial electrochemistry 1986-11, Vol.213 (1), p.31-42
• Main Authors: Amatore, Christian, Kelly, Richard S., Kristensen, Eric W., Kuhr, Werner G., Wightman, R.M.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Fundamental and applied biological sciences. Psychology; General aspects. Models. Methods; Vertebrates: nervous system and sense organs
• ISSN: 0022-0728
• DOI: 10.1016/0022-0728(86)80595-2

The theory for chronoamperometry has been considered for the case where diffusion involves transport from media with lower diffusion coefficient and reduced volume fractions to a medium of unrestricted diffusion adjacent to the electrode. An analytical expression is developed in spherical coordinates for the special case of slow charge transfer kinetics and conditions where steady state behavior is approached, that is, for the experimental case of interest here. It is shown that the form of the resulting expression is similar to that obtained for slow charge transfer in homogeneous media. However, the expression obtained in restricted media is dependent on the radius of the media adjacent to the electrode and the volume fraction of the outer media. The chronoamperometric response of disk-shaped voltammetric electrodes in rat brain tissue is found to agree with the model predicted by these expressions. Evaluation of the data with the model enables an estimate of the size of the region of free diffusion next to the electrode to be made.