Low impedance pH sensitive electrochemical devices that are potentially applicable to transcutaneous PCO2 measurements.
Two cases of low impedance, non-glass membrane electrodes for pH measurement were evaluated: (I) Metal--metal oxide electrodes and (II) Reduction-oxidation electrodes. The fundamental cause of oxygen sensitivity of metal-metal oxide electrodes were examined and three approaches for its suppression were proposed. For the case of Sb--Sb2Ox electordes, oxygen sensitivity can be attenuated partially by cell loading, either directly across the reference electrode or indirectly across a third slave electrode. In a PO2 range of 8--54 kPa, more than 95% of the PO2  response can be suppressed by loading the cell emf to half of tis open-circuit value. The oxygen sensitivity also was observed to diminished by grinding the metal-metal oxide and pressing it under high pressure into a pellet electrode. Other metal-metal oxide electrodes that have promise in transcutaneous  measurement are the Pd-PdO2 electrodes. The redox electrodes are typified by the Quinhydrone electrode. A membrane Quinhydrome electrode showed a sensitivity of 56 mV/Decade at 37 degree C and no oxygen sensitivity up to 50 kPa and a drift of 1 mV/h over a 24-h period. However, the stability deteriorated over a long-term period.
D001784:Blood Gas Analysis / Q000295:instrumentation*; D002245:Carbon Dioxide / Q000097:blood*; D004553:Electric Conductivity; D004566:Electrodes; D006863:Hydrogen-Ion Concentration; D008567:Membranes, Artificial; D008670:Metals; D010084:Oxidation-Reduction; D010087:Oxides; D010313:Partial Pressure; D012867:Skin
D008567:Membranes, Artificial; D008670:Metals; D010087:Oxides; D002245:Carbon Dioxide