Kate Penrod
Fourier-Transform Infrared Spectroscopy, FT-IR Microscope, and Raman Spectroscopy
Spring 2013
Purpose:
The objective of this experiment is to become familiar with the background, theory, and standard operating
procedures of the Varian Fourier-Transform Infrared Spectrometer, the Varian Fourier-Transform Infrared Spectrometer
with Microscope, and the Varian Raman Spectrometer. Upon completion of this laboratory exercise, the knowledge
gained from the experiment will be passed on to classmates.
Introduction:
Fourier-Transform Infrared Spectroscopy (FTIR) is used to identify the bond types of a molecule/mixture.
Typically, FTIR data is qualitative, but some quantitative data can also be obtained. Microscopy gives us the ability to
focus an infrared beam on a given area of a sample. It also makes us able to probe smaller samples, such as carpet and
fiber samples. Raman spectroscopy uses scattered radiation corresponding to the vibrational modes of the molecule(s)
of interest. Our Varian system is an FTIR with a microscope accessory and a Raman accessory. In this laboratory exercise,
organic solvents will be analyzed by FTIR, fibers will be analyzed FTIR Microscopy, and pain relievers will be analyzed by
Raman spectroscopy.
Procedure-FTIR:
Standard Operating Procedure:
 Make sure instrument is on
 Move black lever between FTIR and Raman down
 Open Varian Resolutions Pro
 Select IR scan
 Select Rapid scan
 Set electric tab parameters (Speed: 20 KHz, Filter: 5, UDR: 2)
 Set optics parameters (Source: Mid-IR, Beam: Internal, Detector: DTGS, Beamsplitter: KBr Broadband, Accessory:
None, Optical Filter: None, Aperature: 4 cm-1 and 2000 cm-1)
 Click Setup and adjust Selectivity until reading is between 1-5 V
 Run Background scan
 Run samples and convert to %T
 Close software to shut down
Lab Procedure:
 Analyze 3 organic solvents and known mixtures of these solvents
 Analyze one unknown mixture of the solvents
Procedure-FTIR Microscope:
Standard Operating Procedure:
 Fill microscope detector with liquid nitrogen
 Insert ATR crystal
 Open Varian Resolutions Pro
 Select Microscope under Current Scan
 Select Rapid Scan and use parameters from FTIR
 Run Background scan
 Run samples and convert to %T
 Close software to shut down
Kate Penrod
Fourier-Transform Infrared Spectroscopy, FT-IR Microscope, and Raman Spectroscopy
Spring 2013
Lab Procedure:
 Analyze known fibers
 Analyze one unknown fiber
Procedure-Raman:
Standard Operating Procedure:
 Fill the Raman dewar with liquid nitrogen
 Wait 20 minutes
 Make sure FTIR is on
 Wait 10 minutes and top off the dewar
 Turn on power supply to laser (press switch and turn key)
 Ensure that levers on either side of the Raman are switched on
 Ensure that the lever inside the Raman is up with bypass closed
 Prepare sample in capillary tube with a depth of about 1 inch
 Prepare solids in 4 inch NMR tube
 Be sure to use the correct holder for the correct tube
 Center the sample on the red holographic dot by adjusting the x, y, and z knobs
 Open Varian Resolutions Pro
 Select Raman Scan (IR Source: Off, Beam: Right, Detector: Raman ge, Beamsplitter: Quartz Near IR, ATR Crystal:
None, Optical Filter: Holographic Notch, Aperature: Open)
 Select Laser tab and turn on diode
 Press shutter switch in front of Raman
 Set Raman power to the highest setting
 Adjust value of laser control current to 600-700 mW
 Click setup and adjust centerburst to its maximum (use x,y, and z knobs)
 Click Scan
 Repeat for all samples
 Turn off laser, close shutter, remove sample, turn off laser key and switch
 Leave instrument on
Lab Procedure:
 Analyze known painkillers
 Analyze one unknown painkiller
Data:
FTIR data from Day 1 can be found on page 71 of Instrumental Notebook
FTIR Microscope data from Day 2 can be found on page 74 of Instrumental Notebook
No Raman data were collected due to errors with the instrument
Kate Penrod
Fourier-Transform Infrared Spectroscopy, FT-IR Microscope, and Raman Spectroscopy
Representative FTIR Data:
% Toluene
% 2-Propanol
% 2-Butanone
Toluene 1 (%T)
Toluene 2 (%T)
100
0
0
25
25
50
33
55.80993568
0
0
100
50
25
25
33
42.44863388
40.111
n/a
n/a
74.956
73.473
59.428
65.393
59.525
9.5458
n/a
n/a
48.981
46.638
28.032
35.91
29.873
0
100
0
25
50
25
33
7.072249589
2-Propanol
(%T)
n/a
20.246
n/a
68.76
44.002
63.664
58.589
75.143
Spring 2013
2-Butanone
(%T)
n/a
n/a
0.054294
4.1811
14.052
18.065
3.9065
8.8219
Calibration Curve for FTIR Data:
80
Calibration Curves for Toluene, 2-Propanol, 2-Butanone
Mixtures (FTIR)
70
% Transmittance (%)
60
y = -0.4399x + 83.173
R² = 0.9698
y = -0.5102x + 59.33
R² = 0.9558
50
Toluene 1
Toluene 2
2-Propanol
40
2-Butanone
y = -0.6095x + 79.454
R² = 0.9677
30
Linear (Toluene 1)
Linear (Toluene 2)
Linear (2-Propanol)
Linear (2-Butanone)
20
y = -0.1833x + 16.593
R² = 0.5756
10
0
0
20
40
60
Mass Percent (%)
80
100
120
Kate Penrod
Fourier-Transform Infrared Spectroscopy, FT-IR Microscope, and Raman Spectroscopy
Calculations for FTIR:
Toluene 1:
y=-0.439x+83.17
y=59.525 x=53.86104784
2-Propanol:
y=-0.609x+79.45
y=75.143 x=7.072249589
Toluene 2:
y=-0.510x+59.33
y=29.873 x=57.75882353
2-Butanone:
y=-0.183+16.59
y=8.8219 x=42.448633
Spring 2013
Discussion and Conclusion:
Infrared spectroscopy is very useful for qualitative data, but it is difficult to generate quantitative data from
FTIR. The calibration curves generates from the FTIR data in this laboratory exercise were not of high quality. The 2butanone curve had an R2 value of 0.575, which is analytically unacceptable. The other calibration curves were better,
but the quality was still less than stellar. Using these calibration curves, we were able to determine that the relative
percentages of the components in the unknown were 56% toluene, 7% 2-propanol, and 42% 2-butanone. This does not
sum to 100%, so it is evident that the percentages are inexact, but the data generated is still useful. It is likely that the
relative order (primarily toluene, followed by 2-butanone, very low concentration of 2-propanol) of the concentrations is
correct, although the numbers may not be entirely representative of the sample.
The microscopy portion of this experiment was interesting, though did not yield entirely useful data. The library
indicated that all samples matched all library entries, indicating that our spectra were of low quality. The images
obtained (page 74 in Instrumental Notebook) were clear and the weave patterns were visible. Unknown B was
tentatively identified as an acrylic/wool mixture, but this identification is inconclusive because wool was not analyzed as
a standard, nor was an acrylic/wool mixture. The unknown spectrum did not conclusively match any of our standard
spectra, so identification cannot be performed with any degree of analytical certainty.
The Raman was not functional during this experiment, but it was useful to learn that SpectroPhysics is not very
helpful in troubleshooting instruments, as our Raman accessory has been down for approximately 90% of the semester.
Overall, the FTIR is a user-friendly instrument, but it is important to obtain clean spectra. Our spectra were not
of highest quality, and this experiment could have been improved significantly if we had waited until consistent spectra
were obtained before analyzing the results. This experiment also could have been improved by analyzing more
standards for the microscopy portion.