tailieunhanh - Modern Analytical Cheymistry - Chapter 11

Electrochemical Methods of Analysis Trong chương 10, chúng tôi kiểm tra một số phương pháp phân tích dựa trên sự tương tác của bức xạ điện từ với vật chất. Trong chương này chúng ta chuyển sự chú ý của chúng tôi với các phương pháp phân tích trong đó một thước đo tiềm năng, phí hiện hành hoặc, trong một tế bào điện hóa phục vụ như tín hiệu phân tích. | Electrochemical Methods of Analysis I n Chapter 10 we examined several analytical methods based on the interaction of electromagnetic radiation with matter. In this chapter we turn our attention to analytical methods in which a measurement of potential current or charge in an electrochemical cell serves as the analytical signal. 461 462 Modern Analytical Chemistry 11A Classification of Electrochemical Methods Although there are only three principal sources for the analytical signal potential current and charge a wide variety of experimental designs are possible too many in fact to cover adequately in an introductory textbook. The simplest division is between bulk methods which measure properties of the whole solution and interfacial methods in which the signal is a function of phenomena occurring at the interface between an electrode and the solution in contact with the electrode. The measurement of a solution s conductivity which is proportional to the total concentration of dissolved ions is one example of a bulk electrochemical method. A determination of pH using a pH electrode is one example of an interfacial electrochemical method. Only interfacial electrochemical methods receive further consideration in this text. Interfacial Electrochemical Methods The diversity of interfacial electrochemical methods is evident from the partial family tree shown in Figure . At the first level interfacial electrochemical methods are divided into static methods and dynamic methods. In static methods no current passes between the electrodes and the concentrations of species in the electrochemical cell remain unchanged or static. Potentiometry in which the potential of an electrochemical cell is measured under static conditions is one of the most important quantitative electrochemical methods and is discussed in detail in Section 11B. The largest division of interfacial electrochemical methods is the group of dynamic methods in which current flows and concentrations .