Thermo Scientific 074114, Руководство оператора

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Dionex PDA Operator’s Manual
48
Doc. 065378-01 1/12
If the sample wavelength is 372 nm, you might select a reference
wavelength of 425 nm because both wavelengths are within the visible
spectrum (380 to 800 nm) of the tungsten lamp.
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
d
310 nm.
When programming a 3D channel, the reference wavelength (if set) must be
within the 3D range. 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.
The active reference mode minimizes baseline drift and is ideal for gradient
analyses, where the baseline may shift. This mode also helps compensate for
fluctuations in ambient temperature caused by air conditioning.
•
To cancel the active reference mode, enter Off as the reference wavelength.
The intensity reading at the time of autozero will be used as the reference
intensity.
When running an isocratic analysis in a laboratory with stable ambient
temperature, operating the detector with the active reference mode turned off
ensures the lowest baseline noise. It also ensures that fluctuations in signal
intensity in the reference wavelength do not cause additional noise.
NOTE When you enter Off as the reference wavelength setting,
the reference bandwidth is not used. The reference value
is the first data point of the sample wavelength and
bandwidth after autozero.
Example Chromatogram: Selecting the Reference Wavelength
Figure 3-7 shows the results obtained from two different channels within
the same run. When the reference wavelength mode is Off (i.e., the active
reference mode is cancelled), the baseline drift is –120 P AU/hour. When
the active reference mode is selected, the baseline drift is reduced to –
40
P AU/hour.