ThermoFisher Scientific Vanquish VH-D10, Operating Manual

Page: 104 / 196

6 • Operation
Page 104 Vanquish Diode Array Detectors (VH-D10) Operating Manual
Slit Width
A narrow slit width results in a smaller optical bandwidth and provides a
better optical resolution (the ability of the detector to distinguish
between single wavelengths) which is required for analytes with fine
spectral structures (such as benzene).
Set a value for the slit width that it is not smaller than the smallest value
of all bandwidths and bunch widths used for measurement. If the
smallest value is greater than 8 nm, select a slit width of 8 nm.
The setting of the slit width affects all signal channels and the 3D field.
6.7.6 Selecting the Reference Wavelength and Bandwidth
The reference wavelength and bandwidth can be used to correct the
measured signal from the sample.
Reference Wavelength
Interfering substances can absorb in addition to the absorption of the
analyte in the sample. The absorption of the interferences adds to the
measured signal from the analyte. As a result, this can lead to errors in
the measurement of the analyte concentration. Interfering absorption
frequently results from a changing absorption of the eluent or refractive
index effects. Refractive index effects can particularly occur with
separations with gradients.
If the interfering substance absorbs over a wide spectrum range, the
effect of the interfering absorption on the measured signal can be
reduced mathematically. For this purpose, the absorption is measured at
the measurement wavelength, and at the same time at a reference
wavelength. To correct the signal, the absorbance measured at the
reference wavelength is subtracted from the absorption at the
measurement wavelength.
TIP The use of a reference wavelength can result in additional
interference in the chromatogram. Use the reference wavelength
carefully and only in special cases. In most cases, measurement without
a reference will provide better results.
You can set the reference wavelength separately for each signal channel
and the 3D field.