Thermo Scientific 074114, Руководство оператора

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Dionex PDA Operator’s Manual
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Doc. 065378-01 1/12
Sample Wavelength
The Dionex PDA measures absorbance over all wavelengths from 190 to 800 nm.
The deuterium lamp optimizes the UV range (190 to 380 nm), while the tungsten
lamp optimizes the visible range (380 to 800 nm). Set the sample wavelength at
the wavelength with the absorbance maxima for the analytes of interest.
When the analyte wavelength maxima are known, the Dionex PDA can run five
separate wavelengths without the necessity for collecting spectra. Collecting
individual wavelengths instead of the spectra offers two advantages: it uses less
disk space and it eliminates the need to perform extractions for analyses that do
not require spectral data.
If little is known about the analytes in the sample, collect spectra over the full
wavelength range (using both lamps). Although this requires more disk space, it
provides complete information about the analytes and the spectra can be used to
determine peak identity, purity, and wavelength maxima.
Bandwidth
The bandwidth defines a wavelength range around the wavelength at which the
chromatogram is measured. Increasing the bandwidth increases the number of
different wavelength signals averaged at each point in time. As the bandwidth
increases, baseline noise decreases; however, this may decrease the signal,
especially of those peaks that exhibit spectral peak maxima.
Select a bandwidth that provides the resolution required to achieve the desired
sensitivity. Selecting a wider bandwidth reduces baseline noise, but may also
reduce peak height. For narrow spectral peaks, select narrow bandwidths.
Example Chromatogram: Selecting the Bandwidth
Figure 3-6 illustrates how selecting a wide bandwidth for both the sample
and reference wavelengths reduces noise by averaging over a wavelength
range. The operating conditions are:
Sample wavelength = 254 nm
Reference wavelength = Off
Flowing water at 1.0 mL/min, 10.35 MPa (1500 psi)