Ion-Selective Microelectrodes

PH and ion-selective microelectrodes are rapidly finding an increasing number of applications in the study and control of living (and nonliving) systems. They are unique in their capacity to measure chemical species without altering natural or controlled environmental conditions. Furthermore, these potentiometric tools measure the activity of the chemical species in contrast to conventional ones that measure total concentration. The "Workshop on IonueSelective Microelectrodes" is designed to provide an insight into the principles, theory, fabrication, techniques, present limitations, goals, and applications of some of these tools.The importance and types of microelectrodes and guidelines for their application in biological systems are discussed by Berman. Their present limitations are reviewed by Durst. He warns that their use in analyzing living matter should be approached with caution because of the ill-defined nature of biologic systems. Techniques are presented next for the fabrication of pH (Hebert), antimony (Green and Giebisch, and Malnic et al.), oxygen (Whalen), then single-barrelled (Wright, Walker and Ladle, Morris and rnjevic) and double barrelled (Zeuthen et al., and Khuri) potassium and chloride liquid ion-exchanger microelectrodes. Difficulties with and fabrication of reference and glucose electrodes are covered, respectively, by Durst and Wright, and Bessman and Schultz. Applications of pH and ion-selective microelectrodes are described in microanalysis (Wright), measurement of intracellular ion activity and calculation of equilibrium potentials (Brown and Kunze), and then studies of the kidney (Wright, Malnic et al., and Khuri), brain (Zeuthen et al., Morris and Krnjevic), frog heart (Walker and Ladle), and human skeletal muscle (Filler and Das). In addition, actual and potential clinical applications, respectively, of pH (Filler and Das) and glucose (Bessman and Schultz) electrodes are reviewed.