IR, Raman & IR Microscopy
Introduction:
Fourier Transform Infrared Spectroscopy (FTIR) detects the vibration characteristics of
functional groups in a sample. Chemical bonds bend, contract, or stretch in such a manner that is
unique to each functional group when they are exposed to the FTIR’s infrared light. This
movement creates a spectrum of wavelength absorbances. This method is used for both
qualitative and quantitative analysis of compounds.
Raman Spectroscopy, on the other hand, is generally just used for qualitative analysis of
compounds. It is based on the inelastic scattering of monochromatic light, which forms a
spectrum that can be analyzed to give the functional groups in an analyte. Microscopy is used to
focus an infrared beam on a very specific area of a sample in order to analyze the sample. This
is commonly used to look at carpet fibers.
Purpose:
The purpose of this lab is to be able to run the FTIR and Raman instruments and interpret
the data collected. Three organic solvents and mixtures will be analyzed with the IR. Different
carpet fiber samples will be looked at using the microscope and then used to try to match an
unknown.
Procedure:
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Run three organic solvents through the IR
Identify unique components of each spectrum
Run a mixture of solvents through the IR
Run different mixtures of the three solvents
Run an unknown mixture and determine the concentration of each component
Learn how to operate the IR in Microscopy mode
Obtain spectra for known fibers
Match fibers collected with the known fibers
SOP
FTIR:
1. Make sure than the instrument is on.
2. Make sure that the black lever between the FT-IR and the Raman is down
3. Double click on the Varian Resolutions Pro icon in the top right of the display.
4. In the Current scan menu on the bottom of the screen select IR scan.
5. From the Collect menu at the top of the screen select Rapid scan
6. The Electronics tab parameters should be:
speed: 20 KHz
Filter: 5
UDR: 2
7. The Optics tab parameters should by:
IR Source: Mid-IR
Beam: internal
Detector: DTGS
Beamsplitter: KBr Broadband
Accessory: none
Optical filter: none
Aperture: 4 cm-1 at 2000 cm-1
8. Click setup. The voltage reading should be between 1-5V. If not, change the
selectivity
9. Click background to run a background scan
10. Return to rapid scan from the collect menu and click scan
The transformers menu allows you to convert to %T
11. To shut down, close Varian Resolutions Pro and LEAVE EVERYTHING ON
Raman Spectroscopy:
1. Fill the blue dewar with liquid nitrogen and wait 20 minutes then top off.
2. Make sure the FTIR is on
3. Turn on the laser power supply switch and then turn the key to the on position
4. make sure the lever between the Raman and FTIR is up, the lever between the
Raman and microscope is down, and the internal lever in the Raman should be up,
meaning bypass closed
5. double click on the Varian Resolutions Pro icon to open software
DON’T USE SOFTWARE UNTIL SAMPLE IS LOADED (SEE TROUBLESHOOTING)
6. From the current scan menu select Raman scan
7. The optics parameters should be:
IR Source: off
Beam: right
Detector: Raman Ge
Beamsplitter: quartz near IR
Accessory: FT-Raman
ATR Crystal: none
Optical filter: holographic notch
Aperture: open
8. Select the laser tab and click turn on diode
9. Press the shutter switch on the front of the Raman (to open) and turn the power
to its highest, 3
10. Under the laser tab, adjust laser control current until the Raman display reads
between 600-700 mW
11. Click setup. If filled with noise, click autoscale (the four arrows)
12. Adjust same with X, Y, and Z, knobs until the centerburst is at its maximum
13. Click scan
14. To shut down: collect menu> Raman scan> Laser tab and click turn diode off.
Press the shutter button (closed), remove your sample, turn off the laser power supply and
turn key to off position, and exit Varian Resolutions Pro. Leave everything else on!
Data/Results:
Day 1:
Goal: Run three organic solvents through the FTIR. Then run different mixtures of solvents
through the instrument. Run an unknown as well and compare to the different spectra to
determine what the unknown is. Run samples through the Raman instrument.
Today, we were able to successfully run both the FTIR and the Raman instruments. Our
three organic solvents were 2-butanone, 2-propanol, and toluene. The spectra from the FTIR
showed peaks that matched up to where peaks for each sample should be. After running the
solvents, we ran mixtures of the solvents at different ratios. The four ratios were 1:1:1, 2:1:1,
1:2:1, and 1:1:2. An unknown mixture was also run. Next, we ran two samples on the Raman
instrument. The spectrum collected from this instrument was not as readable as the spectrum
from the FTIR. We first ran a solid acetaminophen sample. We ran this twice since the first
time it was difficult to read the peaks due to the excess background noise. Afterwards, we ran a
liquid methyl salicylate sample, to see if we could get a better spectrum with a liquid sample
rather than a solid sample. This sample did produce a better spectrum, however, there was still a
lot of background noise.
Day 2:
Goal: Look at fibers through the microscopy instrument
Today, we attempted to use the FTIR microscope to look at fiber samples. First, we had
trouble getting the desired voltage. The reading was supposed to be between 1.5 and 5. The
highest value we could get was a little over 1 (about 1.030), however, Donna told us it should be
fine to run as long as it stayed over 1. We ran a 50-poly, 50-cotton sample. We were able to
take a picture of the sample using the microscope, however, it was difficult to see when we
printed it out. The spectra of the data we collected did not turn out well either. There was a lot
of noise and it was difficult to pick out distinguishable peaks.
Conclusion:
This week we learned how to use the FTIR, Raman, and FTIR microscope instruments.
For the FTIR, we looked at three different organic solvents and then combined them at different
ratios to compare the spectra. Then we ran an unknown mixture to compare to the known ratios
and determine what it is. After comparing the spectra, it was determined that the unknown we
ran was the 1:1:2 mixture. All of the spectra we collected were easy to read and comparable to
one another. For the Raman instrument, we ran two different samples, one solid and one liquid.
We had a little bit of trouble finding the center-burst and when we did find it, there was a lot of
background noise on the spectra, which made it hard to analyze. The FTIR microscope was
difficult to work with since no other group had used it yet. We were able to take a picture of a
sample and run an analysis on it, however, the spectra was unreadable.
There were a couple problems with the lab. At first, the student operating procedures
were not online so we had to research how to use the instruments and look for the packets next to
the instruments in lab. Another problem was with the Raman instrument. Our spectra, no matter
if it was a solid or a liquid, had a lot of background noise which made it very difficult to analyze.
Overall, the experiment was a success since we were able to successfully use all the instruments
and collect data from each.