TBS-380 Mini-Fluorometer Operating Manual
11
4 General Considerations for Analysis
4.1
Handling Samples
1. Be cautious not to spill samples into the sample chamber. Promptly wipe any spills.
2. The TBS-380 is very sensitive and even small amounts of material left behind from a previous sample
may result in errors. Use a clean cuvette or disposable cuvette for each reading.
3. Fill the cuvette to the minimum required volume, significant error will result if it is not filled enough. A
minimum volume of 2 mL in a 10x10 mm cuvette or 50
µ
L in the Minicell is required for best results.
4. When taking readings, the cuvette MUST BE CLEAN AND DRY. Moisture and condensation on the
outside can result in erroneous readings.
5. Minute bubbles in samples will also cause errors in readings. Be sure not to introduce bubbles into
samples. Particular care must be taken with the Minicell. Tapping the outside cuvette wall slightly will
often help dissipate bubbles.
4.2
Linear Range and Quenching
The linear range is the concentration range in which the readout of the TBS-380 is directly proportional to
the concentration of the fluorophore. The linear range begins with the smallest 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 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 the fluorophore.
0
1
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3
4
5
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7
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2
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8
10
12
Fluorophore conc.
R
el
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e F
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rescen
ce U
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