Liquid Chromatography Detectors - The Fluorescence Detector > The Multi Wavelength Fluorescence Detector > Page 62
Fluorescence Detector Program
|Time (seconds)||Wavelength of Excitation Light||Wavelength of Emitted Light|
|0||280 nm||340 nm|
|220||290 nm||320 nm|
|340||250 nm||385 nm|
|510||260 nm||420 nm|
|720||265 nm||380 nm|
|1050||290 nm||430 nm|
|1620||300 nm||500 nm|
Figure 40. Separation of a Series of Priority Pollutants with Programmed Fluorescence Detection
The separation illustrates the clever use of wavelength programming to obtain the maximum sensitivity. During development both the wavelength of the excitation light and that of the emission light were changed to provide maximum sensitivity for the particular solute.
The detector can provide fluorescence or excitation spectra by arresting the flow of mobile phase when the solute resides in the detecting cell and scanning either the excitation or fluorescent light. (This is the same technique as that used to provide UV spectra with the variable wavelength UV detector). As a consequence, it is possible to obtain excitation spectra at any chosen fluorescent wavelength or fluorescent spectra at any chosen excitation wavelength. Thus, even with relatively poor spectroscopic resolution many hundreds of spectra can be produced, any or all of which (despite many spectra being very similar) can be used to confirm the identify a compound.