A Excitation Signals

In the first and simplest voltammetric method, the potential of the working electrode is increased or decreased at a typical rate of 2 to 5 mV/s. The cuirent, which is usually in the microampere range, is then recorded to give a voltammogram, which is a plot of cuiTent as a function of applied potential. 

A supporting electrolyte is a salt added in excess to the analyte solution. Most commonly, it is an alkali metal salt that does not react at the working electrode at the potentials being used. The salt reduces the effects of migration and lowers the resistance of the solution. 

The working electrode is the electrode at which the analyte is oxidized or reduced. The potential between the working electrode and the reference electrode is controlled. Electrolysis current passes between the working electrode and a counter electrode. 

In other words, the current in the electrochemical cell is proportional to the voltage output of the op amp. The value of the current can then be calculated from the measured values of and the resistance R. The circuit is called a current-to-voltage converter. 

In operation, the linear-scan voltage generator sweeps the potential between the reference and working electrodes, and the current in the cell is monitored by op amp C. The output voltage of op amp B, which is proportional to the current I in the cell, is recorded or acquired by a computer for data analysis and presentation.  

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Figure 5.8 (a) Excitation signal for alternate drop differential pulse polarography. (b) Total current response for alternate drop differential pulse polarography. 

Figure 23-26 (a) Excitation signal for stripping determination of Cd and Ctr. (b) Anodic stripping voitammo-sram. 

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