FTIR: STANDARD OPERATING PROCEDURE
BEFORE USE:
- Make reservation with online system
- Fill cooling tank with liquid nitrogen
AFTER USE:
- Clean all sample waste and pellet-maker
- Put away all equipment and tools
Bring along the following to run FTIR: Sample, dry KBr, several pairs of gloves, Kim-wipes, spatula, memory stick
I)
Filling Cooling Tank with Liquid Nitrogen
1) Always use thermal-protective gloves when handling liquid nitrogen!!
2) Open top-most round gray cover on the upper left side of the instrument.
3) Remove black stopper and insert the funnel with a metal shaft attached to its base.
4) SLOWLY pour liquid nitrogen into the funnel until the liquid bubbles out from the base of funnel (~1 liter).
5) Remove the funnel, replace the black stopper, and close the round gray cover.
6) WAIT at least 20 minutes before using the FTIR instrument to allow it to cool down.
** The large white Dewar (container) across from the FTIR supplies the FTIR liquid nitrogen **
- The FTIR nitrogen supply comes from the leftover NMR nitrogen.
- If the Dewar is empty, politely ask an NMR person to help you fill the Dewar with liquid nitrogen.
They may do it for you on their own, or they may need you to carry the Dewar to the NMR room.
- You do not need the Dewar completely filled; just a few liters will be enough.
** Please check the liquid nitrogen amount at least one day before using the FTIR**
- You should give NMR people plenty of time to schedule this additional task.
It is NOT proper to expect an NMR person to instantly stop his/her work to fill the FTIR nitrogen Dewar.
II) Making Sample Pellets
Preparing Sample:
1) Use gloves to reduce the transfer of oils and water to the pellet-maker and/or your pellet.
2) Clean with Kim-wipes and then snap together the two pieces of the pellet-maker base.
3) Into the shaft of pellet-maker base, GENTLY insert one of the mirrored disks with its mirror up.
*Do NOT force the disk into the shaft! Disks scratch easily and must be kept mirror smooth!
4) Using mortar and pestle, thoroughly grind together about 1 mg of sample with 50 mg of dry KBr.
* Your literature may report different ratios of sample to KBr – just keep your ratio consistent.
* Move quickly once you have exposed KBr to the air – KBr is highly hygroscopic.
5) Sprinkle the grinded sample+KBr on top of the mirrored disk and ensure even coverage.
6) Into the shaft, GENTLY insert the other mirrored disk with its mirror down.
7) Into the shaft, GENTLY insert the metal piston rod and GENTLY push it into the shaft until it stops.
Pressing Sample into a Pellet:
1) Place the constructed pellet-maker into the center of the press.
2) Hand-tighten the screw with the top handle so it makes good contact with the pellet-maker.
3) Close the valve on the right-hand side by turning the handle clock-wise.
4) Pump the press until the load is 10 tons. Press the pellet for ~5 minutes.
5) Release the valve on the right-hand side by turning the handle counter-clock-wise.
6) Unscrew the top handle and remove the pellet-maker from the press.
7) Gently separate the two pieces of the pellet-maker base.
8) Use the metal piston rod to push the pellet out of the shaft. Do not touch the pellet with bare hands!
** Remember, the best pellets are thin and transparent **
To create the best pellet for your particular sample, try altering:
- the ratio of sample to KBr that you grind together
- the amount of grinded sample+KBr that you add to the pellet-maker
- the total time you press the grinded sample+KBr in the pellet-maker
III) Setting-Up an Experiment
1) Open the OMNIC program on the desktop.
2) From the drop-down menu in the pop-up window, choose the first “Transmission E.S.P.” option; click OK.
3) Click “Collect” in the toolbar, then choose “Experiment Setup…”.
4) In the “Collect” tab:
- Enter the desired number of scans as a multiple of 32 (256 is the highest; 32 is the lowest)
- Enter the desired resolution (the default of 4 cm-1 is very common)
- Choose the final format of your spectrum display (usually either Absorbance or %Transmittance)
* You can switch between the two displays after the spectrum is collected *
- Choose the desired correction (usually H2O and CO2 correction)
- Click the box for “Automatic atmospheric suppression”
- If the “Save automatically” box is checked, the program will still NOT automatically save spectrum
* You must manually save each spectrum into your personal folder in the SPECTRA folder *
- Choose when you want a background collected (recommend BEFORE EVERY sample)
5) In the “Bench” tab, ensure the gain is within acceptable range (peak-to-peak should be between 3 and 9).
If the gain is not within this range, do NOT operate instrument.
- Wait another 10 minutes. If the gain is still outside acceptable range, notify the responsible user.
6) In the lower right corner of the “Bench” tab, it is recommended to change the range to 4000 to 800 cm-1
7) Click the “OK” button at the bottom of the window
IV) Collecting Spectrum
*Recommend that first three steps below be performed while the KBr pellet is forming in the pellet-maker*
1) Install KBr pellet accessory and place “Screen C” over the left-hand-side laser opening
2) Clear instrument of any sample and close the FTIR lid
3) On the computer, click “Collect” in the toolbar, then choose “Collect Sample”
- Enter a spectrum title, if you would like
- Click OK twice to collect the background
* The background (and spectra) will be multiple scans – lower left corner of screen shows progress.
4) While the background is collected, GENTLY place the pellet into the metal pellet holder
5) After the background is collected, insert the metal pellet holder into the instrument and click “OK”
6) After the spectrum is collected, click “Yes” to view the spectrum
7) Save the spectrum to your personal folder (the red spectrum will be the ONLY one saved)
V) Ending Experiment
1) Close OMNIC software
2) Turn off monitor, leave on CPU. Do NOT turn off the actual FTIR instrument.
3) Clean the pellet-maker with Kim-wipes, NOT paper towels
4) Clean up all waste, samples, gloves, tissue, or anything else you brought into the FTIR area
VI) Miscellaneous Notes
- To stop collection of spectrum:
- Click the “pause” button in the lower right-hand of screen. Then close that individual window.
- To reduce noise in the spectrum:
- If only in lower end -> “Experiment Setup”, “Bench” tab – set the spectral range to 4000 to 800 cm-1
- If generally noisy -> Increase the number of scans or make a thinner pellet
- Adjust the laser to go through a thin region of the pellet:
- The height of the metal pellet holder can be changed with the screw under the holder
- Adjust the pellet in the metal pellet holder. Remember, do not touch the pellet with bare hands!
- To correct baseline
- “Process” from toolbar, then “Automatic Baseline Correct”
- To smooth noise
- “Process” from toolbar, then “Automatic Smooth”