Dionex ICS-3000 - Page 83

2 • DC Description
Doc. 065031-04 1/08 67
Analytical vs. Scanning Waveforms
The pre-programmed analytical waveforms supplied with Chromeleon
are designed for quantitative analysis of specific compounds (alcohols,
amino acids, carbohydrates, etc.). With analytical waveforms, integration
occurs either while a single constant potential is being applied over time
(see the example waveform in Figure 2-24
) or while a series of stepped
potentials are being applied (see the example waveform in Figure 2-25
).
With scanning waveforms, integration occurs while the potential is being
increased linearly over time (see the example scanning waveform in
Figure 2-30
). Although scanning waveforms are typically not as useful
for quantitative analysis as analytical waveforms, when used to collect 3D
amperometric data, scanning waveforms can be optimized to provide
characteristic I-t plots (see Section 2.16.7
). Comparison of I-t plots of a
known substance with an unknown can help to identify unknown peaks or
to determine whether a substance is coeluting with another.
Figure 2-30. Example Scanning Waveform
1.0
-2.5
-1.0
1.0
2.0
0.5
1.5
0.0
0.0
Time (Seconds)
E1
E2
E3/E4
E3.
E4
. Oxidative cleaning potential
Reductive cleaning potential
E1
E2
. Pre-adsorption potential
. Scanning potentials
Potential
(Volts)
Integration