4: Sample Experiments
Note
Do not put the sample itself in the path when taking a reference spectrum, only the
solvent.
4. Click the Store Reference spectrum icon on the toolbar or select Spectrum | Store Reference
from the menu bar to store the reference. This command merely stores a reference spectrum in
memory. You must select File | Save | Reference from the menu bar to permanently save the
spectrum to disk.
5. Block the light path to the spectrometer. Then, take a dark spectrum by clicking the Store Dark
Spectrum icon on the toolbar or by selecting Spectrum | Store Dark from the menu bar. This
command merely stores a dark spectrum in memory. You must select File | Save | Dark from the
menu to permanently save the spectrum to disk.
Note
If possible, do not turn off the light source when taking a dark spectrum. If you must turn
off your light source to store a dark spectrum, allow enough time for the lamp to warm up
again before continuing your experiment. After the lamp warms up again, store a new
reference scan.
You must take a dark spectrum scan before measuring absorbance.
6. Put the sample in place and ensure that the light path is clear. Then, take an absorbance
measurement by clicking on the Absorbance Mode icon on the toolbar or selecting Spectrum |
Absorbance Mode from the menu. To permanently save the spectrum to disk, click the Save
icon on the toolbar or select File | Save | Processed from the menu bar.
Note
If you change any sampling variable (integration time, averaging, smoothing, angle,
temperature, fiber size, etc.), you must store a new dark and reference spectrum.
Transmission Experiments
Transmission is the percentage of energy passing through a sample relative to the amount that passes
through the reference. Transmission Mode also displays the portion of light reflected from a sample, since
transmission and reflection measurements use the same mathematical calculations. The transmission is
expressed as a percentage (%T
λ
) relative to a standard substance (such as air). OOIBase32 calculates %T
λ
(or %R
λ
) with the following equation:
S
λ
- D
λ
%T
λ
=
R
λ
- D
λ
x 100%
20 220-00000-000-02-0605
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