Linear voltage ramp

In cyclic voltammetry, we apply the triangular waveform in Figure 17-22 to the working electrode. After the application of a linear voltage ramp between times t0 and f, (typically a few seconds), the ramp is reversed to bring the potential back to its initial value at time t2. The cycle may be repeated many times. 

Differential pulsed voltammetry (DPV) is a technique in which potential pulses of fixed but small amplitudes are superimposed periodically on a linear voltage ramp. The most commonly used working electrode is the SMDE and one pulse is applied for each drop. The mV pulse is applied near the end of the life of the mercury drop. Current is measured once before the pulse and after the pulse. The difference between the currents is plotted against potential (Figure 5.8). The resultant peak-shaped current-voltage signal, which... 

The voltage sweep is identical to that used in conventional differential pulse polarography (Fig. 4.3b). It consists of a linear voltage ramp on which small pulses of 10-100 mV amplitude and about 50... 

Differential pulse polarography - on to a conventional rising linear voltage ramp is imposed a very short potential pulse of small fixed amplitude, one pulse towards the end of each drop lifetime the... 

This method is based on superimposition of a small amplitude sine-wave voltage E over the linear voltage ramp (see Figure 1). 

Figure 17-12 Voltage profiles for voltammetry (a) linear voltage ramp used in vitamin C experiment (b) staircase profile for sampled current polarography. Inset (c) shows how faradaic and charging currents decay after each potential step.

To record the voltammogram of vitamin C in Figure 17-10, the potential applied to the working electrode was varied at a constant rate from -0.4 V to +1.2 V. We call this voltage profile a linear voltage ramp (Figure 17-12a). 

Two recent developments in the measurement technique have resulted in a major reduction in the charging current. Firstly, with the introduction of digitally controlled instruments, the linear voltage ramp applied to the electrodes has been replaced with a stepped (staircase) waveform. The voltage... 

In this technique, a linear voltage ramp is modulated with a sinusoidal alternating voltage of small amplitude (A . = 10-100 mV) and low frequency (/=5-100Hz). The superimposed alternating voltage causes an alternating current, whose size depends on the instantaneous value of... 

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