FTIR and Raman
Fourier Transform Infrared Spectroscopy (FTIR) refers to a fairly recent
development in the manner in which the data is collected and converted from an
interference pattern to a spectrum. An FTIR spectrometer simultaneously collects
spectral data in a wide spectral range. This technique shines a beam containing
many different frequencies of light at once, and measures how much of that beam is
absorbed by the sample. It can identify unknown materials, determine the quality or
consistency of a sample and determine the amount of components in a mixture.
Some of the major advantages of FTIR over the previous techniques include speed
and sensitivity. It can be applied to the analysis of solids, liquids, and gasses.
Raman spectroscopy is a spectroscopic technique used to study vibrational,
rotational, and other low-frequency modes in a system. Raman spectroscopy is
commonly used in chemistry, since vibrational information is specific to the
chemical bonds and symmetry of molecules. Therefore, it provides a fingerprint by
which the molecule can be identified. Raman spectroscopy can be used to study
solid, liquid and gaseous samples. This instrument can be used for both qualitative
and quantitative applications.
Purpose:
We will perform experiments using the FTIR and Raman that will help us
learn how to operate these instruments. Data will be collected and a calibration
curve will be made of the collected data.
Method:
FT-IR
I.
Open Resolution Pro
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Click on the Center burst on towards bottom of the page
Ensure the black flap on the right side of the FT-IR is pushed down
Ensure you see the center burst, and a number in the left corner ranging from 1.2-5
Check the parameters on the right side
The scan dialog box should appear
Check Parameters in Electronics Tab
Scans to co add – 16
Save range – 4000-700cm-1
Check Parameters in Optics Tab
IR-Source – Mid-IR
Beam – internal
Detector – DTGS-Det#1
Beamsplitter – KBR Broadband
Accessory – None
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Source - 2cm-1 at 2000cm-1
Microscope Box – Detector: Left, Optics Mode: Reflectance
o Go to Collect tab at the top
 Hit scan button
 Name the standard
o Take a screen shot of your background & polystyrene
 Click the print screen key on the keyboard (located on the
right side near top)
 Open up the Paint application in the start menu
 Hold ctrl+V to paste the picture into paint
 Save the image to the desktop and put it on a flashdrive to
put into notebook
 Repeat the same steps for the polystyrene
o You can now go back to the graph in the resolutions pro program
 Select the polystyrene sample graph and change the
absorbance to % transmittance by selecting “%
transmittance” under the transforms menu at top
Varian FT-RAMAN
Fill The RAMAN blue dewar with liquid nitrogen (wait 20 min)
Make sure the FT-IR instrument is ON (located in back of instrument)
Top off the dewer with (l) nitrogen after 10 min
Turn on the power supply to the laser located on the floor (press switch
and turn key to on)
V.
The two levers on either side of the raman must be switched to on.
VI.
The lever inside the raman should be up with the bypass closed.
VII.
Prepare sample and put solid in capillary tube to a depth of 1 inch
VIII. Liquids are placed in a 4 inch nmr tube
IX.
There are diff. sample holders for the different tubes.
X.
Center the sample on the red dot on the holographic filter.
XI.
The red dot, is not actually red, it’s more of a pale pinkish. To find it,
lower the lid about halfway and then adjust the X, Y, and Z knobs to
center it.
XII.
Open Varian Resolution Pro on the desktop.
XIII. From the current scan menu select raman scan
1. Ir source: off
2. Beam: right
3. Detector: raman ge
4. Beamsplitter: Quartz Near IR
5. ATR Crystal: None
I.
II.
III.
IV.
6. Otical filter: Holographic Notch
7. Aperture: Open
XIV. Select laser tab click turn on diode
XV.
Press the shutter switch in front of raman
XVI. Set the raman power to the highest of 3
XVII. Return to software and the laser tab and adjust the value of the laser
control current to 600-700 mW
XVIII. Click setup and center burst should appear. This is far less defined than
the center burst seen with the ft-Ir. Click the autoscale icon at bottom of
screen Using xyz knobs and adjust the position of the sample holder until
the center burst peak is at a maximum. Adjusting the y position is most
helpful. If you are having trouble finding the center burst, play around
with the knobs for a few more minutes, but if you’re still unsuccessful,
press the shutter button, open the lid, and re-center the sample on the red
dot by eye.
XIX. Click scan
XX.
Shutting down
a. Turn of laser by selecting raman scan, and laser tab click turn off
diode
b. Press the shutter button on the front of the raman to close the shutter
c. Remove the sample
d. Turn off laser (turn of key, turn off switch)
e. Do not turn off computer, ftir, or raman accessory
Data:
FTIR Microscope was currently not working so we could not perform an experiment on
it.
FTIR
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Sample One: Toluene
Sample Two: 2-Butanone
Sample Three: 2-Propanol
Mixture One: (1:1:1) 33% Each
Mixture Two: (1:1:2) 25% 2-Propanol/2-Butanone 50% Toluene
Mixture Three: (1:2:1) 25% Toluene/2-Butanone
50% 2-Propanol
Mixture Four: (2:1:1) 25% Toluene/2-Propanol
50% 2-Butanone
Unknown (1 ppm)
**NOTE: All spectral data is located in notebook
Calibration Curves:
2-Propanol
98
% Transmittance
93
y = -0.7799x + 111.49
R² = 0.9829
88
83
78
73
68
20
25
30
35
40
Concentration (%)
50
2-Butanone
20
18
% Transmittance
45
y = -0.3426x + 26.702
R² = 0.936
16
14
12
10
8
20
25
30
35
40
Concentration (%)
45
50
Toluene
29.5
% Transmittance
27.5
25.5
y = 0.223x + 15.284
R² = 0.78
23.5
21.5
19.5
20.5
25.5
30.5
35.5
40.5
Concentration (%)
45.5
50.5
Results of Unknown:
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Contained all three compounds (Toluene, 2-butanone and 2-propanol)
Toluene: 23% Transmittance
2-Butanone: 14% Transmittance
2-propanol: 96% Transmittance
Raman:
 Sample One: Acetaminophen
 Sample Two: Toluene
 Sample Three: Methyl Salicylate
**Data located in notebook**
Conclusion:
Unfortunately, we were only able to use two out of the three instruments
because the microscope was not working. The FTIR and Raman were interesting to
use. The most difficult part about the raman was trying to center the laser. That
consumed the largest portion of our time. We realized that by aligning it with your
eyes first before shutting it made a huge difference. The data for the raman was hard
to be interpreted also. It was difficult to distinguish the correct peaks that uniquely
identified that particular substance. We believe that a large amount of peaks were
due to solvent effects. I am interested to see the variety of products that can be run
through the FTIR because I could possibly use it in my independent study research.