IR, Raman, & IR Microscopy Lab
Introduction:
Infrared spectroscopy is a type of instrumentation that uses the wavelengths found
in the infrared region of the electromagnetic spectrum to determine a particular compound.
One of the most widely used types of infrared spectroscopy is known as the Fourier
Transform Infrared Spectroscopy, which is named after the mathematical algorithm it uses
to interpret the data it receives. This instrument works by passing shining a beam of
infrared energy through a chemical sample, where some of the wavelengths of light are
absorbed by the sample whereas others simply pass through, or transmitted. Since each
chemical compound absorbs/transmits individually, no two spectrums are similar and
therefore each compound has a “molecular fingerprint” of frequencies of that compounds
molecular bonds/structure. Raman Spectroscopy is another type and it utilizes a laser as an
energy source through the sample and the scattered light is then collected from the sample.
The instrument measures the vibrational frequencies that are characteristic to each
particular molecule, bond, etc. From these frequencies, the type of compound can then be
identified.
Purpose:
There are two procedures in this particular lab, each with its own individual
purpose. In the first FTIR procedure, the purpose of the experiment is to first learn the
basics of how the IR operates by running various organic samples through the instrument
and identifying the resulting peaks. After identifying the peaks of the organic samples,
mixtures of these samples will then be run in order to produce a calibration curve, from
which the identity of an unknown mixture will be derived.
The second procedure in this experiment Instrumental Analysisuses the FTIR
microscope, in which the purpose is to understand the basics of operating the instrument
and then to run unknown fiber samples through the IR and uses the observations and data
collected to determine what the fibers might be.
Instrumental Procedure:
Varian 3100 Excalibur Series FT-IR
1.
2.
3.
4.
5.
Make sure that the FTIR is on (should not be turned off but have to check)
The black lever between the FT-IR and the Raman should be pushed down
Open the software by double-clicking ‘Varian Resolutions Pro’ icon
From ‘current scan’ drop down menu at bottom of screen, select ‘Basic IR Scan.’
From ‘collect’ menu, select ‘rapid scan’ and make sure parameters are set (under
‘electronics’ tab) to speed- 20KHz, filter-5, UDR- 2, and save range- custom 4000700 cm-1.
6. Select the optics tab and set parameters to:
a. IR source – Mid-IR
b. Beam – Internal
c. Detector –DTGS
d. Beamsplitter – KB r Broadband
e. Accesory – None
f. ATR Crystal –None
7.
8.
9.
10.
g. Optical Filter –None
h. Aperture – Not installed
Click setup
Center burst should read between 1 and 5. Click ‘ok.’
To run background scan, click ‘background’ and make sure no sample is in the
compartment.
To run sampel, click ‘collect’, the in rapid scan menu, click’scan’
Varian 600 UMA FT-IR Microscope
1.
2.
3.
4.
5.
Fill the Microscope detector with liquid nitrogen
Insert ATR crystal
To set up software, open software by click ‘varian resolutons pro’
From ‘current scan’ drop down, select method file ‘microscope’
From collect menu, select rapid scan, check that parametres are set up same as
above procedure states
6. Run a background scan and then run the samples
Experimental Procedure:

FTIR:
1. Obtain three different organic compounds from the available stock
samples.
2. Run each sample individually to identify the characteristic peaks for
each.
3. Run a 1:1:1 ratio solution of each and identify the characteristic peaks.
4. Repeat #3 for a 2:1:1. 1:2:1, and 1:1:2 ratios.
5. Make an unknown sample and attempt to identify the ratio of each
organic compound
Data:
1. FTIR:
Compound
2-propanol
Toluene
2-butanone
1:1:1 ratio
Key Peak
Peak Description
3000-3500 (broad peak)
2800-2900
2800-3100
1500 + 1600 (twin peaks)
790
2800-3000
~1700
3000-3500 (broad peak)
2800-3000
~1700
1500 + 1600 (twin peaks)
~790
OH alcohol
CHsp2/sp3
CHsp2/sp3
Alkene (aromatic)
mono sub. Benzene
CHsp2/sp3
C=O
OH alcohol
CHsp2/sp3
C=O
Alkene (aromatic)
mono sub. Benzene
2:1:1 ratio
1:2:1 ratio
1:1:2 ratio
Unknown ratio

3100-3400 (broad peak)
2800-3000
~1700
1500 + 1600 (twin peaks)
~790
2800-3000
~1700
1500 + 1600 (twin peaks)
~790
2800-3100
~1700
1500 + 1600 (twin peaks)
~790
2800-3100
~1700
1500 + 1600 (twin peaks)
~790
OH alcohol
CHsp2/sp3
C=O
Alkene (aromatic)
mono sub. Benzene
CHsp2/sp3
C=O
Alkene (aromatic)
mono sub. Benzene
CHsp2/sp3
C=O
Alkene (aromatic)
mono sub. Benzene
CHsp2/sp3
C=O
Alkene (aromatic)
mono sub. Benzene
Unknown Ratio Determination: 0:1:2 (2-propanol:toluene:2-butanone)
2. Raman
Compound
Key Peak
Peak Description
2-propanol
3100-3000 tall peak
~3000
~900
3000-3100 tall peak
1600
~900
OH alcohol
CHsp2/sp3
mono sub benzene
OH alcohol
C=O
ortho sub benzene
Toluene
methyl salicylate
3. IR Microscopy
a. The IR microscope was not working properly, so we were not able to
complete this part of the procedure.
Conclusion:
Overall, I was quite confident in the overall results obtained from this
experiment. Both the IR and Raman results were easily obtained, and the results
from each test were conclusive and easily analyzed as each spectrum corresponded
to its respective compound. They were easily utilized to compare relative
concentrations of each compound in each mixture as well as to ultimately determine
the mixture of compounds that was prepared for us. However, the only real trouble
experience with this experiment was just the fact that the microscope was not
functioning properly, and therefore that part of the procedure were not able to be
completed.