title: Digital simulation of chronoamperometry at an electrode within a hemispherical polymer drop containing an enzyme: comparison of a hemispherical with a flat disk electrode.
abstract: Current-time and steady state current behaviour was simulated for the cases of a hemispherical and flat inlaid disk electrodes located under a hemispherical polymer drop containing an enzyme which converts a substrate diffusing into the drop into a product that is electroactive at the electrode. As well, a cylindrical electrode with length much greater than its diameter and coated with a layer of polymer/enzyme was treated. The ratio of steady state currents at the hemispherical to the disk electrode is not, as has sometimes been assumed, always equal to π/2; indeed this is only approached for polymer drops with large spillover ratio, that is, having a radius much larger than that of the electrodes. Steady state currents for all electrode geometries (including the cylinder) go through a maximum for some spillover ratio and then approach a constant value for larger spillover ratios. This constant value is the same as that for the diffusion limited current in a semi-infinite medium. For a cylindrical electrode, the steady state current tends towards zero for large spillover ratios.
authors.affiliation: Department of Chemistry, Aarhus University, 8000 Aarhus C, Denmark. Electronic address: britz@chem.au.dk.
authors.forename: Dieter
authors.initials: D
authors.lastname: Britz
authors.forename: Jörg
authors.initials: J
authors.lastname: Strutwolf
mesh_terms: D000465:Algorithms; D015374:Biosensing Techniques / Q000295:instrumentation*; D003198:Computer Simulation; D004058:Diffusion; D055664:Electrochemical Techniques / Q000295:instrumentation*; D004566:Electrodes; D004800:Enzymes, Immobilized / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008954:Models, Biological; D008956:Models, Chemical; D011108:Polymers / Q000737:chemistry*
chemical_list: D004800:Enzymes, Immobilized; D011108:Polymers
keywords: Digital simulation; Enzyme systems; Finite differences; Michaelis–Menten kinetics; Numerical simulation; Polymer drop