Fluorolog-3 v. 2.2 (11 Jul 2002)
Applications
10-4
Fluorescence detection of highly scattering
samples
Qualitative and quantitative determinations normally are difficult to ascertain from
highly scattering samples. Typically, fluorescence signals are dwarfed by stray or scat-
tered light from the sample. The flexibility of the Fluorolog
®
-3 systems, however, al-
lows the introduction of a double-grating emission spectrometer, thereby improving the
system’s stray-light rejection. With a single-grating emission spectrometer, scattered
light from the sample often finds its way through the exit along with the selected band
of emitted light. However, when the band is re-dispersed by the double-grating spec-
trometer, most stray light is stripped away as the band passes through the exit slit to the
emission detector.
Quantum-yield calculations
Among the many features unique to Fluorolog
®
-3 systems, is the capacity to measure
fluorescence-related parameters required to calculate the quantum yield for samples in
solution. This includes recording excitation-source intensity and calculating the area
under the corrected emission spectra.
Characterizing complex mixtures via
synchronous scanning
The fluorescence spectrum of a complex mixture often contains overlapping spectral
features representative of the mixture and revealing no indications of the contents of the
sample. A spectrum of this nature is all but useless.
Synchronous scanning
offers a so-
lution to this problem.
Simultaneous scanning of the excitation and emission spectrometers with a constant
offset between them yields an intensity proportional to the product of the emission and
excitation intensities. This resulting spectrum often can be analyzed readily.
The figure below shows the emission scan and the synchronous scan of a mixture of
polynuclear aromatic hydrocarbons.
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