Control of Electrode Aging by a Periodic Anodization Technique
The long-term use of noble metal electrodes for amperometrically monitoring oxygen tension in blood and tissue has been hampered by the unstable nature of the electrode calibration. Changes in sensitivity (current per unit oxygen tension) as rapid as 20% per hour have been reported . If this drift were constant, it would, in principle, be simple to correct for; however, increasing and decreasing trends separated by plateau regions are most frequently encountered [2,3]. In some cases, changes in sensitivity have been attributed to protein deposition or to poisoning by sulfur-containing molecules , but such mechanisms cannot account for the drift observed with electrodes immersed in pure saline solutions [2,3]. The latter phenomenon, usually referred to as “electrode aging”, can best (and perhaps only) be explained by supposing an interrelationship between the electrode’s catalytic activity and its redox history. This, of course, is a concept well documented in the electrochemical literature . Of particular importance here is that some electrochemical studies [6,7] suggest that, at least for Pt electrodes, strong oxidizing treatments, such as exposure to concentrated nitric acid or anodization at elevated potentials, may result in more stable electrode behavior. In this report, we present evidence, based on in vitro tests in physiological saline, indicating that the aging phenomenon can be controlled by periodically restoring the electrode surface to a pseudostable level of catalytic activity via in situ anodization.
KeywordsOxygen Tension Cathodic Polarization Electrode Aging Anodic Pulse Electrode Stability
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