Agilent Technologies 1260 Infinity Quaternary LC VL, Руководство системы и краткое справочное руководство

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Agilent 1260 Infinity Quaternary LC VL Manual and Quick Reference 73
Optimization of the Agilent 1260 Infinity Quaternary LC VL
3
Optimizing Detection with DAD
Optimizing Selectivity
Quantifying Coeluting Peaks by Peak Suppression
In chromatography, two compounds may often elute together. A conventional
dual-signal detector can only detect and quantify both compounds
independently from each other if their spectra do not overlap. However, in
most cases this is highly unlikely.
With a dual-channel detector based on diode-array technology, quantifying
two compounds is possible even when both compounds absorb over the whole
wavelength range. The procedure is called peak suppression or signal
subtraction. As an example, the analysis of hydrochlorothiazide in the
presence of caffeine is described. If hydrochlorothiazide is analyzed in
biological samples, there is always a risk that caffeine is present which might
interfere chromatographically with hydrochlorothiazide. As the spectra in
Figure 22 on page 73 shows, hydrochlorothiazide is best detected at 222 nm,
where caffeine also shows significant absorbance. It would therefore be
impossible, with a conventional variable wavelength detector, to detect
hydrochlorothiazide quantitatively when caffeine is present.
Figure 22 Wavelength Selection for Peak Suppression
With a UV-visible detector based on a diode array and the correct choice of a
reference wavelength setting, quantitative detection is possible. To suppress
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