BAS 100B/W Instruction Manual page 74

Therefore, for a reversible process, i
square root of the scan rate, υ
As discussed above, there are many parameters that can affect the shape of the CV
curve. Slow electron transfer kinetics can increase the separation of the peak
potentials (∆E ), and the rate constant for electron transfer can be calculated by
p
examining the variation of ∆E
between the working and reference electrodes can also increase ∆E
uncompensated resistance can be lowered or eliminated using electronic iR
compensation (see iR Compensation under the Control menu).
Another application for CV is the study of the reactions of electrolyzed species.
These are generated on the forward scan, and their reactivity can be examined on the
reverse and subsequent scans. Qualitative estimates of reaction rates can be obtained
by varying the scan rates.
The simplicity and speed of CV means that it is often used as the first technique to
characterize a redox system, and it is a very powerful technique for qualitative
analysis of kinetics and mechanism. However, quantitative kinetic measurements
using CV generally require digital simulation, since there is no other way to separate
the effects of slow electron transfer and chemical reactivity.
The charging current that is present in CV and LSV limit their usefulness as
techniques for quantitative analysis. However, LSV is used as one of the techniques
for the detection of trace metals using stripping voltammetry. This is discussed in
more detail in section 10.6.
It is important to note that the potential wave form used for CV and LSV on the BAS
100B/W (and other digital instruments) is a staircase wave form, since it is
impossible to generate digitally a true linear wave form. There has been much
discussion on the equivalence of "digital staircase" CV and LSV and "analog" CV
and LSV, and it has been shown that variation of the parameters used for the
"staircase" techniques can lead to significant differences. Theoretical studies have
shown that equivalence can only be guaranteed if the potential step height of the
staircase wave form is less than 0.3/n mV (where n = number of electrons
transferred). Therefore, for Scan Rates in mV/s, the potential wave form used on the
BAS 100B/W for CV and LSV is identical to a true analog linear wave form, since
the step height is 0.1 mV. However, for Scan Rates in V/s, the step height is 1.6 mV,
so small inequivalences may arise.
BAS has a considerable number CV Notes, together with articles and Capsules that
describe the applications of CV (the articles and capsules are listed below). These can
beobtained at no charge from BAS.
is proportional to the concentration, C, and the
p
1/2
.
with scan rate. However, uncompensated resistance
p
10-6
. The effect of
p