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72 211_0010 - ROXY Exceed user manual - rev 04
Scanning voltammogram
An alternative for the chromatographic construction of an I/E relationship is
the application of scanning voltammetry (ROXY Exceed only). In a scan-
ning voltammetry experiment the working electrode potential is ramped up
and down between two preset potentials (E1 and E2) and the current is
measured while the analyte is continuously flushed through the flow cell.
This is repeated as many times as desired. The rate of voltage change
over time is defined as the scan rate (mV/s).
Fig. 28. Scanning voltammetry potential waveform.
The current is plotted against the working potential to give a voltammo-
gram (I/E curve). An example is shown in Fig
. 29 . A difference with a hy-
drodynamic is that in scanning voltammetry, no HPLC separation is in-
volved. The signal is the sum of all EC active substances. It takes only a
few minutes to construct a
scanning voltammogram. This is an advantage,
especially when a number of analytes have to be characterized. However,
it is a prerequisite to have the
pure analyte dissolved in buffer. A scan of
the buffer (blank) should be used to distinguish between solvent peaks and
analyte peaks.
Any contamination in the buffer may lead to artefacts.
t2 t1
W
ork
ing
Pot
ent
ial
(V)
Time (Seconds)
E1
E2
t0
Scanning Voltammetry Waveform
S
ca
n
r
a
te
(
V
/s)