10
The step-by-step procedure for making an absorption/transmittance measurement
is as follows:
1.
Turn on the spectrophotometer by pressing the power switch (the power switch
is located on the right side of the back of the instrument.) In order to stabilize
the lamp and detector; allow the instrument to warm up for at least 15 minutes.
2.
Turn the wavelength control knob to the desired wavelength.
3.
Fill a test tube full with blanking solution and with a tissue, wipe off any residue
and fingerprints on the outside of the test tube. If the test tube has no guide
mark, some may wish to use a permanent marker to draw an approximate ¼
inch vertical line at the lip of the test tube or cuvette (this ensures that you
minimize the bearing of any differences in reflection due to small changes in the
thickness in the wall of the test tube). Place a test tube into the sample
compartment with the test tube guide mark aligned with the mark at the top of
the compartment (this mark is located at the front of the sample compartment).
Be sure that the test tube has been firmly pressed into the sample compartment
and the lid of the sample compartment has been closed.
4.
Adjust the display to 100%T and 0.00A by turning the 100%T/ 0A knob.
5.
Remove the test tube from the sample compartment and empty the blank
solution.
6.
Rinse the test tube twice with small volumes of the sample solution to be
measured, then fill the test tube 2/3 full with the sample solution and wipe it
clean.
7.
Place the test tube in the sample compartment, aligning the guide marks (if
any).
8.
Close the lid of the sample compartment. (Sample site can also be
covered)
9.
Read the %T and absorbance from the digital display.
10.
Remove the test tube from the sample compartment, empty it and repeat
Step 7
to
10
for any additional samples.
Making Measurements at Different Wavelengths
Repeat
Step 2 to Step 10
above and remember to blank your
spectrophotometer whenever a measurement is being made at different
wavelengths. In addition, when operating at a fixed wavelength for an extended
period of time, check to make sure that the transmittance reads 100%T when the
