Hoefer DQ300 - Manual (Page 24)

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4.2 Linear Range and Quenching
The linear range is the concentration range in
which the readout of the DQ300 is directly
proportional to the concentration of the fluoro-
phore. The linear range begins with the small-
est detectable concentration and extends to an
upper limit (concentration) that is dependent
upon the properties of the fluorescent material,
the filters used, and the path length. See the
diagram below.
A nonlinear relationship is seen at higher
concentrations where the fluorescence signal
increases more slowly than the change in
concentration. At even higher concentrations,
readings will begin to decrease even though the
sample concentrations are increasing. This effect
is known as “signal quenching.”
Linearity may be checked by diluting a sample 1:1
or some other convenient ratio (be sure to use an
appropriate blank for the dilutions). If the sample
is within the linear range, the reading will decrease
in direct proportion to the dilution. If the read-
ing does not decrease in direct proportion to the
dilution or if the reading increases, the sample is
beyond the linear range of your fluorophore.
TBS-380 User’s Manual 15
A nonlinear relationship is seen at higher
concentrations where the fluorescence signal
increases slower than the change in concentration.
At even higher concentrations, readings will begin
to decrease even though the sample concentrations
are increasing. This effect is known as "signal
quenching."
Linearity may be checked by diluting a sample 1:1
or some other convenient ratio (be sure to use an
appropriate blank for the dilutions). If the sample
is within the linear range, the reading will
decrease in direct proportion to the dilution. If the
reading does not decrease in direct proportion to
the dilution or if the reading increases, the sample
is beyond the linear range of your fluorophore.
4.3 Temperature Considerations
Fluorescence is temperature sensitive. As the
temperature of the sample increases, the
fluorescence decreases. For greatest accuracy,
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