Electrode recovery potential.
In some instances the same electrodes are used for stimulation and then for recording a bioelectric event immediately after the stimulus. However, after the current pulse there remains an electrode potential that decays quasiexponentially. We have designated this falling potential the electrode-recovery potential. This study investigated the recovery potentials of single electrodes of rhodium, stainless steel, platinum and platinum-iridium in contact with 0.9% saline at room temperature (25 degrees C) over a current density ranging from 0.1 to 100 mA/cm2 using a constant-current pulse. In all cases, with increasing current density, there was a decrease in the time for the electrode potential to fall to one half of the immediate post-stimulus value. Above about 20 mA/cm2 the decrease in recovery time was smooth with increasing current density. Below 20 mA/cm2, the recovery time was slightly irregular. The shortest recovery times were for platinum and platinum-iridium. The largest decrease in recovery time with increasing current density was for stainless steel, which decreased 10 fold from 0.1 to 100 mA/cm2. The recovery time for rhodium decreased about three-and-one half fold over the same current density range. It was found that the waveform of the recovery potential is not a simple exponential because the Warburg and Faradic components of the electrode-electrolyte interface are current-density dependent. In general, for all current densities studied (0.1-100 mA/cm2), there was a sudden initial fall in electrode potential with cessation of current flow, followed by a very gradual nonexponential decrease in potential.
Mayer
S
S
School of Electrical Engineering, Purdue University, W. Lafayette, IN 47907-1293.
Geddes
L A
LA
Bourland
J D
JD
Ogborn
L
L
D004553:Electric Conductivity; D004558:Electric Stimulation / Q000379:methods; D004566:Electrodes; D004594:Electrophysiology / Q000295:instrumentation*; D007495:Iridium; D008422:Materials Testing; D008954:Models, Biological; D010984:Platinum; D012238:Rhodium; D013193:Stainless Steel
D013193:Stainless Steel; C077763:platinum-iridium alloy; D007495:Iridium; D010984:Platinum; D012238:Rhodium