Square-wave amplitude polarography

Many of the experimental parameters for normal-pulse polarography are the same as with differential-pulse polarography. Differential-pulse polarography is a technique that uses a series of discrete potential steps rather than a linear potential ramp to optimize specific applications (130). Unlike normal-pulse polarography, each potential step has the same amplitude, whereas the return potential after each pulse is slightly negative of the potential prior to the step. In this manner, the total waveform applied to the dropping mercury electrode is very much like a combination of a linear ramp with a superimposed square wave. 

Figure 3.16. Waveforms for pulse and differential-pulse polarography. Curves A and D Excitation signal applied to the working electrode. Curves B and E Instantaneous current observed at a single drop as a function of time. Curves C and F The resulting current-versus-voltage curves. In pulse polarography, square-wave voltage pulses of 40-msec duration are applied to the mercury drop, of drop-life mechanically controlled at 2.5 sec (A) ta,ti,ti,... represent successive drops. The overall rate of increase of the amplitude of the voltage pulses is about...

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