Dionex PDA-100, Руководство оператора

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1 • Introduction
Doc. 031644-02 9/03
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Determination of the correct wavelengths in one run
After all peaks have been detected, the maximum absorbance
wavelength for each peak can be determined. A PDA detector can
collect spectra of each peak and calculate the absorbance maximum.
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Detection of multiple wavelengths
A PDA detector can monitor a sample at more than one wavelength.
This is especially useful when the wavelength maxima of the analytes
are different. Wavelengths can be selected to analyze each compound
at its highest sensitivity.
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Peak purity analysis
It is difficult to determine component purity from a chromatogram.
However, a PDA detector can analyze peak purity by comparing
spectra within a peak. A pure peak has matching spectra throughout
the peak (at all wavelengths).
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Positive peak identification
In liquid chromatography, peak identification is usually based on
relative retention times. When a PDA detector is used, spectra are
automatically collected as each peak elutes. The PDA software
compares the spectra with those stored in a library to determine the
best fit matches; this method increases the likelihood of correctly
identifying peaks.
For example, Figure 1-1 shows an overlay of pyrene and an impurity
(obtained from two consecutive chromatographic runs). Based on 2D
data, or if the run had been performed with a conventional variable
wavelength detector, these peaks would have been misidentified as
the same component.
A PDA-100, under the control of Dionex software with the 3D
option, correctly identified and differentiated the components. The
spectra of pyrene and the impurity (see Figure 1-2) clearly indicate
that the two peaks are different components.