Chemistry Reference
In-Depth Information
periods of time that the pulses are applied. However, after each pulse, the
potential returns to its initial potential, giving the electrode surface time to
return to its initial condition and to compensate for the changes of surface
condition caused by the application of the pulse.
Differential pulse voltammetry
In differential pulse voltammetry (DPV)
69-73
, short pulses (t=10-100 ms)
with limited amplitude (D
E
= 1-100 mV) are superponated to a linearly
increasing DC ramp (Fig. 2.12). This means that besides the current of the
pulse, a DC current also is obtained due to the inclining DC ramp. Practi-
cally, the current is measured before the application of a pulse (
I
1
) and at
the end of the pulse (
I
2
). The first current is attributed to the DC ramp,
while the difference
I
2
-
I
1
reflects the current of the potential pulse. The
resulting voltammograms of the pulse current have a differential shape,
which is illustrated in Fig. 2.13. In Fig. 2.13a, the common voltammogram is
illustrated that would be obtained in linear sweep, cyclic or normal pulse
voltammetry, while in Fig. 2.13b, the differential pulse voltammogram is
shown. As explained above, the signal in differential pulse voltammetry is
the result of the difference between two signals - the signal just before the
pulse and the signal at the end of the pulse. Therefore, it can be seen in Fig.
2.13a that the pulses cover a small fraction of the common voltammogram,
I
2
I
1
Time (s)
2.12
Variation profile of the applied potential in differential pulse
voltammetry.
