Electrochemical Methods of Analysis

Several useful techniques for water analysis utilize electrochemical sensors. These techniques can be potentiometric, voltammetric, or amperometric. Potentiometry is based on the general principle that the relationship between the electrical potential of a measuring electrode and that of a reference 

Electrode potential versus saturated calomel electrode (V) 

FIGURE 18.10 Differential-pulse anodic-stripping voltammogram of tap water at a mercury-plated, wax-impregnated graphite electrode showing detection of metals at subparts-per-billion levels. 

Electrochemical phenomena and processes are nsefnl for the qnantitative and qualitative chemical analysis of varions snbstances and media, inclnding liquids, gases, and solids. The high accnracy of the electrochemical methods of analysis derives from the fact that they are based on highly exact laws (e.g., those of Faraday). 

The following are the major groups of electrochemical methods for chemical 

Conductometry, which measures the electrical conductivity of the electrolyte solution being examined 

Coulometry, which measures the amount of charge Q consumed for the complete conversion (oxidation or reduction) of the substance being examined 

Voltammetry, which determines the steady-state or transient polarization characteristics of electrodes in reactions involving the substance being examined 

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The majority of FI A applications are modifications of conventional titrimetric, spectrophotometric, and electrochemical methods of analysis. For this reason it is appropriate to evaluate FIA in relation to these conventional methods. The scale of operations for FIA allows for the routine analysis of minor and trace analytes and for macro-, meso-, and microsamples. The ability to work with microliter injection volumes is useful when the sample is scarce. Conventional methods of analysis, however, may allow the determination of smaller concentrations of analyte. 

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