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Fourier Transform Infrared Spectroscopy
Standard Operating Procedure
INSTRUMENT:
Varian 3100 Fourier Transform Infrared Spectrometer (FT-IR)
INSTRUMENT START-UP:
 The FT-IR does NOT have a detector cooled by liquid nitrogen
 Make sure the lever between the FT-IR and the Raman is closed (down)
--------------------------------------------------------------------------------------------------------------------PREPARING THE HATR ASSEMBLY:
A. Remove the HATR assembly from the black case stored below the FT-IR
B. Insert the HATR assembly into the FT-IR
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C. Use the trough plate
D. Load the trough plate onto the HATR assembly

If a salt plate assembly will be used, see page 6
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RUN THE EXPERIMENT:
A. Open the Varian Resolution Pro Software
B. From the Collect menu at the top of the screen, select Rapid Scan and check that
the following parameters found in the Electronics tab are selected:
Speed:
Filter:
UDR:
20 KHz
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Save Range: Custom: 4000-700 cm-1
Note: “Resolution,” “Sensitivity,” and “Scans to Co-add” are set to good
starting values by the method. If needed, only these should be changed to affect
the signal/noise of your spectrum
C. Select the Optics tab and be certain to set the following parameters:
IR Source:
Beam:
Detector:
Mid-IR
Beamsplitter: KBr Broadband
Internal
Accessory:
None
DTGS – Det #1 ATR Crystal:
None
Optical Filter: None
Source:
2 cm-1 at 2000 cm-1
Microscope
Detector:
Left
Optics Mode:
Reflectance
THE OPTICS PARAMETERS LISTED SHOULD NOT BE CHANGED AT ANY TIME
D. Click Setup
E. A center burst should appear with a voltage reading in the upper left corner.
This reading should be between 1.5 and 5. If it is not, adjust the sensitivity
(right-hand window). Clicking the 4-way arrow icon will rescale the center burst
to fit the window, if needed.
F. Click OK
---------------------------------------------------------------------------------------------------------------COLLECT A BACKGROUND SPECTRUM:
A. Be sure the sample is not in the sample holder and click on Background
B. Name and save the background scan
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COLLECT A SAMPLE SPECTRUM:
A. Using a glass Pasteur pipet , load the sample onto the trough plate
B. From the Collect menu, select Rapid Scan. Click the Background Tab. Make sure
the background properties box says Status = Exists.
1. If no background exists, it will need to be defined. Click use current and
open to find the background file
2. If the file cannot be found, select collect background after sample
C. Click the Computations tab and be certain the method follows this order:
1. Compute
2. Ratio
3. Truncate
4. Stop
5. Absorbance to % transmittance
D. If the method order is different, click set to default and the method should
return order listed above
E. Click Scan
F. Name your standard and save the spectrum
---------------------------------------------------------------------------------------------------------------ANALYZING THE SPECTRUM:
A. To switch from absorbance to % transmittance, click the Transforms menu and
click % Transmittance.
B. To run a library search, use the following steps:
1. Select the Operations menu
2. Select Varian Search
3. Select Search
4. Under the algorithm section make sure Correlation is selected
5. Select the libraries applicable to your search
6. Click Search
--------------------------------------------------------------------------------------------------------------------CLEANING THE PLATE:
A.
B.
C.
D.
Pour remaining sample into a waste beaker
Use acetone to clean the plate
Use a Kim-wipe to gently wipe the outside (silver) part of the plate
If you are running more samples, load the next sample
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--------------------------------------------------------------------------------------------------------------------INSTRUMENT SHUT-DOWN:
A.
B.
C.
D.
E.
Remove the HATR Assembly
Clean the trough plate with acetone
Close Software
DO NOT log off the computer
DO NOT turn off the instrument
--------------------------------------------------------------------------------------------------------------------WASTE CONSIDERATIONS FOR INSTRUMENTAL CHEMISTRY COURSE:
A. Standards and samples may be disposed in waste container D in the waste hood
B. Container is denoted by Yellow Label tape
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SALT PLATE SAMPLE PREPARATION:
A. Get two salt plates and metal holder located in the desiccator
1. Make sure the salt plates are clear
B. Place one salt plate on the metal sample holder
C. Load the sample using a glass Pasteur pipet
D. Sandwich your sample between the two salt plates
E. Slide the metal cover the salt plate
F. Tighten the screws in a diagonal line (2 screws at a time)
1. Stop tightening the screws when you feel resistance
2. DO NOT OVER TIGHTEN OR YOU WILL BREAK THE SALT PLATE
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--------------------------------------------------------------------------------------------------------------------CLEANING THE SALT PLATE:
A. Use acetone to clean the salt plate
B. Use a Q-tip or Kim-wipe to gently wipe the plate
C. Make sure you clean both plates
D. NEVER USE WATER IT WILL DISSOLVE THE PLATE
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