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Dionex PDA Operator's Manual
Reference Bandwidth
The reference bandwidth is analogous to the conventional bandwidth of a channel.
The purpose of the reference bandwidth is to average several photodiode signals
in a range surrounding the reference wavelength.
It is not necessary to select a reference bandwidth unless you enter a reference
wavelength (i.e., you select the active reference mode). If you enter Off as the
reference wavelength, the reference bandwidth will be the same as the bandwidth.
If you specify a reference bandwidth, it should meet the following criteria:
•
Select a reference bandwidth in an area of the spectrum where the sample
does not absorb.
•
Select a reference bandwidth that is narrow enough not to interfere with
nearby compounds. A wider bandwidth will reduce baseline noise, but may
increase the chance that the sample absorbs in the reference bandwidth; this
will reduce sensitivity.
•
The reference wavelength plus one-half the reference bandwidth must be
within the sample wavelength range selected. The reference wavelength (if
set) must be within the 3D range.
•
If the active reference mode is selected (see
page
47), select a reference wavelength and reference bandwidth in a quiet
area of the spectrum where little absorption occurs. The reference wavelength
plus one-half the reference bandwidth must be within the sample wavelength
range selected; if it is not, the reference wavelength will default to the longest
wavelength. If the data collection rate is 20 Hz, the 3D sample wavelength
range must be 310 nm.
Example Chromatogram: Selecting the Sample Wavelength,
Reference Wavelength, and Reference Bandwidth
Figure 3-8
50
shows the spectrum of caffeine. The operating conditions are:
Sample wavelength = 272 nm
Bandwidth = 5 nm
Reference wavelength = 325 nm
Reference bandwidth = 51 nm
"Reference Wavelength" on
Doc. 065378-01 1/12
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