Fluorolog-3 v. 2.2 (10 Sep 2002)
Optimizing Data Acquisition
4-2
Sample preparation
The typical fluorescence or phosphorescence sample is a solution analyzed in a standard cu-
vette. The cuvette itself may contain materials that fluoresce. To prevent interference, Jobin
Yvon Inc. recommends using non-fluorescing fused-silica cuvettes that have been cleaned
as described above.
Small-volume samples
If only a small sample volume is available, and the intensity of the fluorescence signal is
sufficient, dilute the sample and analyze it in a 4-mL cuvette. If fluorescence is weak or if
trace elements are to be determined, Jobin Yvon Inc. recommends using a capillary cell such
as our 50-µL or 250-µL optional micro-sample capillary cells, which are specifically de-
signed for a small volume. A 1-mL cell (5 mm × 5 mm cross-section) is also available.
Solid samples
Solid samples usually are mounted in the Model 1933 Solid Sample Holder, with the fluo-
rescence collected from the front surface of the sample (see
Components and Accessories
).
The mounting method depends on the form of the sample.
•
Thin films and cell monolayers on coverslips can be placed in the holder directly.
•
Minerals, crystals, vitamins, paint chips, and similar samples usually are ground
into a homogeneous powder. The powder is packed into the depression of the Solid
Sample Holder. For very fine powder, or powder that resists packing (and therefore
falls out when the holder is put into its vertical position), the powder can be held in
place with a thin quartz coverslip, or blended with potassium bromide for better
cohesion.
Dissolved solids
Solid samples, such as crystals, sometimes are dissolved in a solvent and analyzed in solu-
tion. Solvents, however, may contain organic impurities that fluoresce and mask the signal
of interest. Therefore use high-quality, HPLC-grade solvents. If background fluorescence
persists, recrystallize the sample to eliminate organic impurities, and then dissolve it in an
appropriate solvent for analysis.
Biological samples
For reproducible results, some samples may require additional treatment. For example, pro-
teins, cell membranes, and cells in solution need constant stirring to prevent settling. Other
samples are temperature-sensitive and must be heated or cooled to ensure reproducibility in
emission signals. (A thermostatted cell holder with a magnetic stirrer is available: See
Com-
ponents and Accessories
).
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