Ion Selective Sensors and Electrodes Technologies for Industrially, Environmentally and Biologically Significant Ion Measurements - Complete Technical Paper

Ion selective sensors have been used for analytical determination of a wide variety of ions since the 1900??s. Ion selective sensor??s utility and simplicity has replaced other wet analytical methods that were often far slower and more cumbersome to perform. Although it would be impossible to give a comprehensive review of previous work here, (or even to give a complete overview) a brief overview is desirable to properly assess the areas of interest in the current literature and establish its place amongst previous research. In particular, very limited consideration is given to ion selective field effect transistor technologies, due primarily to their very poor commercial acceptance and extensive technological difficulties of their fabrication for the relatively low volume demand in the ion selective measurement industry (including all of the demand for pH sensors) [1, 2]. Most analytical sensors are electrodes of the second kind. As with all electrodes that are not metal-metal ion electrode of the first kind [M|M+], speed of response and reversibility is of critical importance for accuracy and reproducibility of measurements. In fact, the issue of reversibility and consideration of all electrochemical systems as equilibrium processes was one of the major contributions of Nernst. The Nernst equation describes that a change in potential of an electrochemical system is linear to the change of the ion activity (in logarithmic units) of the selected analyte ion. It is clear that the potential is dependent upon temperature.