Instructions for Operation of IR100 Spectrometer
At the start of the lab, your TA will:
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turn the spectrometer and printer on
login with their initials and select “atr” for Available Configurations:
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select SetupàOptions and check the default options. The routine settings include not saving
background scans (these are run manually before every student sample), and not showing the
background scan.
To obtain a sample of your compound:
1. Make sure that the crystal window on the top of the spectrometer is clean. If it is not, you can use
acetone and a kimwipe to clean the window area.
WARNING: halogenated solvents such as dichloromethane or deuterochloroform (your solvent for
NMR) will RUIN the crystal, which costs $900. NEVER USE A HALOGENATED SOLVENT TO
CLEAN THE CRYSTAL WINDOW.
2. Select CollectàBackground to obtain a background spectrum. When prompted, use “b” as the name
for this spectrum.
The air in the room contains molecules such as carbon dioxide and water that absorb IR radiation.
The background scan is used to subtract these signals from your sample’s IR spectrum.
3. Select Collectà sample. When prompted, type in a unique identifying name for your spectrum (e.g.
your initials plus the sample name) but DO NOT CLICK ON THE “ENTER” KEY YET.
If your sample is a volatile liquid, it could evaporate off of the window before you finish typing this
information. You only click on the “Enter” key when you are ready to scan.
4. Apply a small amount of your sample to the crystal window.
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If your sample is a liquid, immediately click on the “Enter” key after application so that the
scanning is completed before your material evaporates.
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If your sample is a solid, you will carefully screw down a metal “anvil” to press it against the
crystal window. The metal plunger has a line etched in it that is used to read the pressure
being applied to your sample. Tighten until that etched line aligns with the “12” mark on the left
side. CAUTION: OVER-TIGHTENING TO A HIGHER PRESSURE CAN BREAK THE
CRYSTAL WINDOW. Once this is done, click on the “Enter” key to collect your spectrum.
The machine will take a series of scans of your compound and add them together. The resulting
spectrum will then be displayed:
5. Select AnalyzeàFind Peaks to obtain frequencies for the absorbances in your spectrum. A line will
be drawn across the spectrum that represents the threshold for peak selection. Peaks above this line
will not be selected. In the spectrum shown below, only the largest peaks have been selected.
To move the threshold, click above or below the line to change its position. In the spectrum shown
below, the threshold was moved up to pick some of the smaller peaks:
If too many or too few frequencies have been selected, the Sensitivity slider may be moved to adjust
the number of peaks picked. This usually won’t be required.
6. Select FileàPrint to print out your spectrum. Make sure that “Landscape” is selected and not
“Portrait”:
Make sure that you have a good printout of your spectrum before continuing to the next step!
7. Select ViewàClear Spectrum to delete your spectrum. Select “No” for saving—your data will not be
saved, so don’t lose your printout!
8. Clean the crystal window and anvil with acetone and a kimwipe so that the spectrometer is ready
for the next user.