6
•
Operation
Vanquish Diode Array Detectors (VH-D10) Operating Manual
Page 103
6.7.5
Optimizing the Bandwidth and Slit Width Settings
As a standard, a bandwidth of 4 nm and a slit width of 4 nm are defined
in Chromeleon. If required, both parameters can be set individually.
The interaction between bandwidth and slit width has a substantial
impact on linearity, baseline noise, selectivity as well as the spectral
resolution of the peak.
Bandwidth
You can accept the standard bandwidth in Chromeleon, or set the
bandwidth to a higher or lower value. For a wider or smaller bandwidth,
the detector can average several single photodiode signals. This process
is referred to
photodiode bunching
. Note the following:
•
The averaging always takes place symmetrically to the selected
wavelength.
•
When performing a detection near the edge of the spectral range
If the bandwidth setting results in an averaging asymmetrically to
the selected wavelength, the detector will correct the setting.
Example:
If you perform a detection at a wavelength of 195 nm with
a bandwidth of 20 nm, the photodiode bunching is set to 190 to
200 nm, i.e. the largest possible symmetrical range around the
detection wavelength. As a result, the bandwidth is changed to
10 nm. This is done to avoid a wavelength shift as would be the case
with an asymmetrical averaging.
The following table serves as guidance for selecting the bandwidth
based on the spectral features of the analyte to be detected:
Spectral Features
Bandwidth
Effect
Samples with extremely fine
spectral features, such as
benzene, and very high
absorptions.
< 4 nm
May increase baseline noise.
Samples for "normal" analysis
with fine spectral features, such
as caffeine.
4 nm –
8 nm
Reasonable compromise
between low baseline noise,
good linearity and low cross-
sensitivity
Samples with broad spectral
features.
> 8 nm
Most suitable for low noise. A
reduced linearity and increased
cross-sensitivity may occur.
Summary of Contents for Vanquish VH-D10
Page 4: ...Contacting Us Page 4 Vanquish Diode Array Detectors VH D10 Operating Manual...
Page 44: ...4 Unpacking Page 44 Vanquish Diode Array Detectors VH D10 Operating Manual...
Page 80: ...5 Installation Page 80 Vanquish Diode Array Detectors VH D10 Operating Manual...
Page 110: ...6 Operation Page 110 Vanquish Diode Array Detectors VH D10 Operating Manual...
Page 162: ...7 Maintenance and Service Page 162 Vanquish Diode Array Detectors VH D10 Operating Manual...
Page 190: ...11 Appendix Page 190 Vanquish Diode Array Detectors VH D10 Operating Manual...
Page 191: ...12 Index Vanquish Diode Array Detectors VH D10 Operating Manual Page 191 12 Index...
Page 195: ...12 Index Vanquish Diode Array Detectors VH D10 Operating Manual Page 195...