Thermo Scientific Dionex UltiMate 3000 Series Operating Instructions Manual page 82

UltiMate 3000 Series:
VWD-3100 and VWD-3400RS Variable Wavelength Detectors
5.5.1.1 Wavelength
When you select a wavelength, make sure that the mobile phase is "transparent", showing
little or no absorption at the selected wavelength. In addition, observe the following,
depending on the selected way of data acquisition:
Single-channel data acquisition
Note the following key criteria for determining the wavelength for a single-channel data
acquisition:
• Sample components should absorb strongly at the selected wavelength. Preferably, select a
wavelength on an absorption maximum. At the selected wavelength no other sample
components should absorb that can falsify the peaks of the sample components of interest.
• If the absorbance spectra of the sample components differ significantly, the measurement
wavelength can be adjusted or switched any number of times during the single-channel
data acquisition. The switching is considerably shorter than one second and should be
performed when no sample components of interest are present in the flow cell. While the
wavelength is switched, no absorption takes place for a short period of time. If the
wavelength is switched during an analysis of a sample component, the peak area is
changed, and a correct quantification is not possible.
For information about adjusting the baseline behavior, see section 5.6.1.4 (→ page 87).
For information about identifying optimum wavelength, see section 5.6.2 (→ page 88).
Multi-channel data acquisition (VWD-3400RS only)
In addition to the above, the VWD-3400RS detector can record chromatograms with a
multi-channel data acquisition. With this data acquisition mode, the detector switches
between two and four wavelengths. The required period of time for this mode depends on
the number and distance of the selected wavelengths. Chromeleon calculates the possible
data collection rate. For wavelengths with small distance the data collection rate can be up
to 5 Hz.
Tip: The optical filters for suppressing higher-order wavelengths are also moved
automatically into the light path with the multi-channel data acquisition.
Sample components with different absorption characteristics can also be analyzed without
complete chromatographic resolution. Data that has been recorded in the multi-channel
mode is reported in different data tracks.
Page 74 Operating Instructions