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5.
General Considerations
5.A. Handling Samples
1.
Take care not to spill liquid into the Sample Compartment. Promptly wipe any spills.
2.
The QuantiFluor™ Fluorometers are very sensitive, and even small amounts of material from
a previous sample may result in errors. Use a clean cuvette for each reading. Thorough and
proper cleaning of cuvettes between sample readings is essential and is especially important if
the same cuvette is used for both the sample and the blank.
3.
The minimum volume is 2ml for 10 × 10mm cuvette, or 50µl and 75µl for the QuantiFluor™-
ST and QuantiFluor™-P Minicell Adapters, respectively.
4.
Ensure that the cuvette is clean and dry on the outside when taking readings. Moisture and
condensation on the outside can result in error.
5.
Minute bubbles in samples will cause errors in the readings. Be sure not to introduce bubbles
into samples. Particular care must be taken with the Minicell Adapter. Slight tapping on the
outside cuvette wall often will help dissipate bubbles.
5.B. Linear Range and Quenching
The linear range is the concentration range in which the QuantiFluor™ Fluorometer readout is directly
proportional to the concentration of the fluorophore. The linear range begins with the smallest detectable
concentration and continues to an upper concentration limit that depends upon the properties of the
fluorescent material, the filters used, and the path length.
A nonlinear relationship occurs at higher concentrations where the fluorescence signal increases at
decreasing rates in relation to the concentration change. At even higher concentrations, readings begin to
decrease despite increasing sample concentrations. This effect is known as "signal quenching."
Linearity may be checked by diluting a sample 1:1 or some other appropriate ratio (be sure to use a
corresponding buffer 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.
5.C. Temperature
Fluorescence is temperature-sensitive. As the temperature of the sample increases, the fluorescence
decreases. For greatest accuracy, read the blank, standard and samples at the same temperature.
Promega Corporation · 2800 Woods Hollow Road · Madison, WI 53711-5399 USA · Toll Free in USA 800-356-9526 · Phone 608-274-4330 · Fax 608-277-2516 · www.promega.com
Part# TM338
Page 16
Printed in USA.
Revised 1/11
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