Basic Anasazi Proton NMR Tutorial
Sample preparation, insertion and removal.
Small glass vials, about 5 mL volume with caps.
Pasteur pipettes with bulb.
Filter paper with small glass funnel.
NMR tubes, 5mm, Wilmad 507-pp or equivalent.
Tetramethylsilane (TMS)
Carbon Tetrachloride (CCl4)
Kim-Wipes.
HOW TO PREPARE BULK SOLVENT:
Prepare bulk solvent by adding tetramethylsilane (TMS) to carbon tetrachloride (CCl4) for a final
concentration of 1.0% (v/v). Bulk solvent can be stored in a laboratory refrigerator.
HOW TO PREPARE YOUR SAMPLE:
For solid samples, place approximately 25 to 50 mg to a clean glass vial and then add about 2 mL of bulk solvent. Mix well until the sample dissolves. Filter out any particulates or undissolved materials. Add about 0.5 to 1.0 mL of the liquid to a clean NMR tube and cap.
For liquid samples, place approximately 1 drop into a clean glass vial and then add about 2 mL of
bulk solvent. Mix well and filter out any particulates or undissolved materials. Add about 0.5 to
1.0 mL of the liquid to a clean NMR tube and cap.
CHECKING THE INSTRUMENT AIR SUPPLY:
THIS SHOULD BE DONE BEFORE INSERTING THE SAMPLE!!!
Check the position of the air pressure shut-off valve on the wall above the magnet. The handle
should be parallel to the pipe and pointing down to turn the air on. If the handle is in the correct
position and no air pressure is seen on the regulator gauge next to the valve (approximately 20
PSIG), consult an instructor. Note that for some shimming routines, the sample must not be
spinning. If this is the case, turn off the air supply using the shut-off valve, not the regulator.
INSERTING THE SAMPLE INTO THE PROBE:
DO NOT FORCE ANY OF THE FOLLOWING STEPS, BE SLOW AND GENTLE!!!
The availability of sample spinners (the little yellow plastic thing with fins) is limited for this instrument, and they can be easily cracked, broken or worn out by misuse. Additionally, NMR sample tubes can be easily broken and present a safety hazard. If you have problems, get someone to help you (your lab instructor, for example).
Hold the yellow plastic spinner with the fins pointing up and press the sample tube GENTLY down through the spinner about two-thirds of the way up the tube. Twisting the tube a little helps. Then lower the tube into the white plastic spinner depth gauge on the front of the magnet. Now GENTLY press the sample tube down until it stops (or push down on the spinner until it stops). Adjustment of the spinner depth is now correct. Lift the sample tube out of the depth gauge by the top and GENTLY wipe off the lower portion of the tube using a Kim-Wipe. Now lift the smoked plastic dust cover on top of the magnet and lower the sample tube into the probe (the large hole under the dust cover). If a slight resistance is felt, GENTLY move the tube around a little until it drops down into the center of the probe. You should hear a whirring noise as the sample begins to spin.
If the sample tube drops into the probe and doesn't begin to spin, even though the air pressure is
OK, press your finger over the lift air vent tube (3mm tube immediately to the left of the probe
hole). This should lift the sample tube out of the probe. If it doesn't, get an instructor to help
you.
REMOVING THE SAMPLE FROM THE PROBE:
Lift the smoked plastic dust cover on top of the magnet. Press your finger over the lift air vent
tube (3mm tube immediately to the left of the probe hole) and the sample will float on the lift air.
Grasp the NMR tube and gently remove it from the probe. Close the plastic dust cover.