IR, Raman, and IR Microscopy Lab
Introduction: The Fourier Transform Infrared Spectroscopy probes the bond types of sample
analyte. It also measures absorbance, emission, transmittance, and photoconductivity of a solvent
or mixture of solvents. This is accomplished by infrared radiation passing through and a sample.
As it passes through a sample, some radiation gets absorbed by the analyte depending on the
chemical bonds that are specific to each functional group in a sample. The rest of the radiation is
transmitted. The FTIR can be used to determine the components and concentration of a sample.
The Raman Spectroscopy focuses the infrared beam on a specific area of a sample. This
spectroscopy can locate and probe a small sample. It is a process of inelastic scattering on
monochromatic laser light. This can analyze solids, liquids, and most gases.
Purpose: The objective for this experiment is to become familiar with the FTIR and the Raman
Spectroscopy. For the FTIR, we will run three organic solvents and identify components of the
spectrum. We will then create a calibration curve by running different mixtures of the three
solvents and observing their wavelength. We will then run an unknown mixture. For the Raman
Spectroscopy, we will analyze fibers with the IR in Microscopy mode.
Procedure:
Procedure: FT-IR:
1. First always make sure the instrument is turned on, but it is usually left on at all times.
2. Check to see if black lever between IR and Ramen is pushed down.
3. Once this is done, open the “Varian Resolutions Pro” on the computer desktop; When opened
click on ‘current scan’ and select ‘basic IR’; then at the top of the screen hit “collect” and select
‘rapid scan’ and follow the parameters.
4. Select optics tab and set parameters but not change them anytime during the experiment; click
setup and should get a reading between 1 and 5, if this not happen adjust the measure on the right
side until there’s a reading between 1 and 5.
5. Perform a background scan and make sure there is no sample in there, if using the trough
make sure it is empty; when background is completed run your sample, go back to collect and
rapid scan and select scan, a spectrum should appear and will be displayed as absorbance. To get
it to % transmittance, select “transform” from the menu and then select %T.
6. To shut down close and save programs but do NOT shut off the IR.
Raman:
1. Fill blue dewar with liquid nitrogen until it overflows, let it sit for 20 min. and then top it off
with more liquid nitrogen.
2. When that is ready turn the laser power on and turn the key behind the instrument, it will
display ”ready” when it has cooled down enough. Make sure the black lever between the IR and
Raman is up and the one between Raman and microscope is down, the lever inside the Raman
should be up as well.
3. Load the sample and make sure to center it on the red dot and then start the program. Click
“Varian Resolutions Pro”, select current scan and switch to Raman Scan. Go to collect at the top
of the menu and select Raman scan, go to the optics tab and check the parameters; you may have
to change them from the IR parameters, but after that do not change them.
4. Select the laser tab and click “turn on diode”, press the shutter which on and set the Raman
power to the highest of 3 ranges.
5. Adjust the power of “laser control current” until laser power reads 600-700mW.
6. Click setup and you should see a center burst, most aren’t really defined but are noticeable, if
no center burst appears, move the X and Y nobs on the front of the Raman to center the sample
more; you may have to open it again and re-center it by eye and then it should work.
7. Click ‘ok’ and hit scan and spectrum should appear; no background scan is required for this
scan.
8. To shut down, turn off laser by clicking “turn off diode” in the laser tab, press the shutter
button and remove sample, turn off laser power supply then the key and switch, do opposite of
how it was turned on. Do NOT turn off computer or Raman/IR.
Data:
2 butanone
%
%
composition Transmittance
100
2
50
7
33
10
25
15
2 propanol
%
%
Composition Transmittance
100
28
50
46
33
55
25
67
Toluene at 1500 cm-1
%
%
Composition Transmittance
100
11
50
30
33
41
25
48
Toluene at 1600 cm-1
%
%
Composition Transmittance
100
35
50
64
33
70
25
79
Results:
2-Butanone
y = -0.151x + 16.351
R² = 0.8702
16
% Transmittance
14
12
10
8
6
4
2
0
0
20
40
60
80
100
120
% Composition
2-Propanol
y = -0.4715x + 73.516
R² = 0.9324
80
% Transmittance
70
60
50
40
30
20
10
0
0
20
40
60
% Composition
80
100
120
Toluene at 1500 cm
y = -0.4729x + 57.092
R² = 0.9731
60
% Transmittance
50
40
30
20
10
0
0
20
40
60
80
100
120
% Composition
Toluene at 1600 cm
y = -0.5624x + 91.244
R² = 0.9896
90
% Transmittance
80
70
60
50
40
30
20
10
0
0
20
40
60
% Composition
Equations:
2- Butanone
y = -0.151x + 16.351
2- Propanol
y = -0.4715x + 73.516
Toluene at 1500 cm
y = -0.4729x + 57.092
Toluene at 1600 cm
y = -0.5624x + 91.244
80
100
120
Unknown
C=O peak
9% = -0.151x + 16.351
x = 48 % 2 - Butanone
OH peak
103% = -0.4715x + 73.516
x = error < 25 %
Toluene
47% = -0.4729x + 57.092
x = 21 % Toluene
Conclusion:
For the 3100 Excalibur FT-IR, we ran three organic compounds and mixtures of 1:1:1, 2:1:1,
1:2:1, 1:1:2, and un unknown. Calibration curves were created. The Toluene peak has good
results. However, the 2- Butanone and 2- Propanol curves did not have good R2 values. When
calculating the percent composition yield of unknown, 21 % Toluene was determined. We
calculated 48% 2- Butanone in the unknown but with the errors in the value, it is not likely.
When calculating percentage of 2- propanol, an error was observed. There may have been many
errors in this experiment. First the mixture concentrations could have not been precise and
therefore altering the calibration curves. Also, the trough could not have been completely clean,
therefore having contamination, and picking up incorrect peaks.
While running the varian FT-raman, we had difficulty in successfully getting a scan. At first 2propanol was attempted and a centerburst did not appear. After asking for help and still not
getting a centerburst, Acetaminophen was attempted. A centerburst appeared but was not very
clear. A scan was run (in notebook) and peaks were observed but there was a lot of noise. After
refilling the liquid nitrogen, acetaminophen was rerun and there was a little less noise. Methyl
salicylate was then run and picked up a good scan, with little noise. Errors in this experiment
could have been not centering the pink dot and not being able to find the centerburst.
On the second day, we attempted to run the microscopy. We were not able to run this
successfully. The voltage range should have been between 1.5 and 5 volts. Even after we had the
highest sensitivity, the voltage was only around 1 volts. We attempted to scan fabrics although
there was a low voltage. While attempting to run an IR, the results came out poor. We were able
to use the microscope and get a clear image of the fabric. After capturing, we had difficulty
finding the image and when printed, the ink ruined the image.