Dual mode antimony electrode for simultaneous measurements of PO2 and pH

Background: In biomedical research and clinical medicine there is a demand for potent sensors to measure the components that make up blond gas analyse s. Today, as when the electrochemical PO2, PCO2 and pH electrodes were firs t introduced, these measurements are usually made with the same type of sen sor technology The aims of: the present study were, firstly, to find out wh ether the platinum cathode in the Clark electrode can be replaced by antimo ny for oxygen measurements (amperometry (A)); secondly, whether, during oxy gen measurements, the inherent corrosion potential of the antimony metal ca n be used for measurement of pH in the same measurement area (potentiometry (P)). Methods: An electrode of purified, crystallographically orientated monocrys talline antimony (COMA) connected to a reference electrode (silver-silver c hloride) was used for the P measurements. Measurements of A (at -900 mV) an d P were made in an aqueous environment regulated for oxygen, pH, and tempe rature. Results: Reproducible oxygen sensitivities of 0.925 nA/% oxygen (2% CV (coe fficient of variation)) (A), 10.7 mV/% (P), and 0.7 mV/% (P) were found in the oxygen range: 0-21%, <5%, and above 5%, respectively The pH sensitivity was 57 mV/pH unit (P). Oxygen and pH measurements were less accurate at ox ygen concentrations close to 0%. Conclusions: Both the oxygen and pH part of the composite electrode signal can be identified by this dual mode technique (A and P). The sensor seems t o be promising as it provides measurements of two separate variables (oxyge n and pH) and also has the desirable characteristics of a solid state senso r.