CLARK ELECTRODE

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References: 9

This is a polarographic electrode used for measuring the concentration of oxygen in blood and gases. The sample is brought into contact with a membrane (usually polypropylene or PTFE - Teflon) through which oxygen diffuses into a measurement chamber containing potassium chloride solution. In the chamber are two electrodes; one is a reference silver/silver chloride electrode and the other is a platinum electrode coated with glass to expose only a tiny area of platinum (e.g. 20 [u]m diameter). The electric current flow between the two electrodes when polarized with a voltage of 600-800 mV determines the oxygen concentration in the solution.

The reaction is very sensitive to temperature and to maintain a linear relationship between the oxygen concentration and the current measured the electrode temperature must be controlled within 0.1[d]C. The electrode is calibrated using two gas mixtures of known oxygen concentration. Such electrodes are used in the blood gas analyser in the clinical chemistry laboratory or in intensive care areas.