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Sample Preparation for the Perkin-Elmer IR Spectrometers
Preparing Your Sample
- The small round NaCl crystal plates must always be kept wrapped in
a clean Kimwipe within their metal containers and stored in a dessicator
when not in actual use, because they are hygroscopic and will pick up
moisture from the air. Ideally, they should not be handled with your
bare hands, because perspiration and oils from your skin will severely
damage their highly polished surfaces.
- Preferably while wearing protective gloves, remove the metal containers
holding the NaCl crystal plates from the dessicator, take out two crystals,
and carefully place them side by side on a clean paper towel. (They
are very fragile and will easily break if dropped).
- Using a clean disposable Pasteur-type pipette, place 2-3 drops of
your liquid sample on the surface of one of the crystal plates, then
slowly slide (to minimize any possible air bubble formation) the second
plate over the sample-containing surface of the first, thereby "sandwiching"
your sample between the two plates. Using a fresh Kimwipe, gently wipe
the edges to remove any excess sample that may have leaked out.
- Open the sample compartment of the spectrometer, and carefully place
the crystals containing your sample on the sample holder, then close
the sample compartment door and proceed to take a spectrum by following
the specific instructions provided for the instrument (If you are
not sure about what you are doing, please ask an instructor for help).
Cleaning the NaCl Crystal Plates When Finished
- After taking a spectrum of your sample, remove (while
still wearing protective gloves) the crystal plates from the instrument,
carefully separate them, and place them on a clean paper towel. Using
a clean Pasteur pipette, thoroughly flush all the surfaces of each
crystal with chloroform (ideally this should be done in a hood
to avoid inhaling chloroform vapors), wrap each crystal in
a fresh Kimwipe, place it back in its metal container, and return
the containers to their storage dessicator.
- Dispose of all used pipettes, paper products, etc. in proper waste
containers, and check to be certain that you have left the work area
clean and neat for the next person.