The Electrochemistry of Gases of Medical Interest and Electrochemical Gas Sensors

Abstract

This chapter discusses the electrochemistry of gases of medical interest and electrochemical gas sensors. Chemical sensors operate by converting a physical or chemical change into a signal which can be interpreted in terms of the concentration of the analyte of interest. In most cases a transducer converts this change into an electrical signal, which is output as a digital or analogue scale. In this respect electrochemical cells are ideal as sensors. The reaction of a substance at an electrode results in changes of an electrical nature—that is, changes in current, voltage or resistance may be generated. These electrical changes are easily measured using quite simple electronic circuitry. Electrochemical devices are also relatively cheap to manufacture or to buy. Clinical gas sensors may cost several hundred to thousands of pounds whereas clinical mass spectrometers cost tens of thousands of pounds. One criticism of electrochemical methods is the possible lack of specificity. There is, however, some specificity inherent in all electrochemical measurements. The chapter reveals that measurement of oxygen concentration or partial pressure is important in many areas. These include aquatic, atmospheric, clinical and laboratory environments. In clinical measurements the monitoring of arterial and veinous oxygen tensions is important (in conjunction with carbon dioxide measurements) in diagnosing and treatment of cardiopulmonary disorders. The measurement of oxygen concentration or partial pressure is usually effected using Clark type sensors.