Monique Gray
Instrumental Analytical Chemistry
Standard Operating Procedure (2012):
Fourier Transform Nuclear Magnetic Resonance
INTRODUCTION
NMR stands for Nuclear Magnetic Resonance. This instrument allows you to analyze the
structure of an organic compound. An advantage of the NMR technique is that it allows you to
determine functional groups and allows you to indentify neighboring carbon-hydrogen bonds
and functional groups relative to particular types of carbon-hydrogen bonds and
hybridizations. Thus, you can determine and analyze the entire structure. FT-NMR can be
used to analyze different types of organic molecules. Some of them are C13, H1, N15, F19, and
P31. These atoms are available to be analyzed because there quantum spin is not equal to
zero. A spinning nucleus within an atom creates a magnetic field, when an alternate magnetic
field is not present the magnetic moment within the nucleus of the atoms will orient itself
randomly. When you apply a strong magnetic field and place an atom between its pole, the
atom’s magnetic properties will align with or against that magnetic moment of the applied
magnetic field. This creates alpha and beta spin states. Those atoms that align with the
magnetic field are considered to be in the alpha state, which implies that they are in a lowerenergy state and those atoms that align against the magnetic are in a much high energy state
and termed beta-energy states. Simple, it takes more energy to align oneself against an
applied magnetic field. The energy difference between the alpha and beta energy states is
what the basis of NMR spectroscopy is based upon. Thus, FT-NMR stands to Fourier Transform
Nuclear Magnetic Resonance, which basically implies that the instrument has the capability of
transforming the time interval associated with the particular molecules and transform its
corresponding time into a frequency (cm-1) via a complex mathematical expression.
PREPARING A SAMPLE
To prepare a sample to the NMR is important to note what tape of sample you have
because solid samples are prepared differently than liquid/aqueous sample.
SOLID SAMPLE
A solid sample needs to be massed to about 80mg. Once you have massed the sample
to about 80mg. Measure out 1mL of chloroform. Then, add both substances to a test tube and
pipette up and down to mix the compounds together. Once, the mixture is done mixing,
obtain a NMR tube with a NMR cap and a small ruler, preferably with a cm measuring scale.
Transfer the mixture to the NMR tube drop wise. Use your rule to measure the height of your
sample. You need your sample to be between 4 and 4.5 centimeters inside the NMR time. If
you go above or below 4 -4.5cm the NMR instrument may not be able to read you sample
property and it will have a hard time locking on to your sample. Once sample is ready cap
with a NMR cap and take to the NMR room.
Monique Gray
Instrumental Analytical Chemistry
**WHEN TRANSPORTTING NMR SAMPLEs BE SURE IT IS TAKEN TO THE NMR ROOM VIA A
BEAKER. ALL SAMPLES SHOULD BE IN A BEAKER. TRY NOT TO TOUCH GLASS NMR TUBE
WITH YOUR FINGERS.
** Also, when labeling the NMR tube you DO NOT write on them, you a take a piece of
paper and poke a hole in it and place NMR tube thru the hole, and label the paper.
LIQUID SAMPLE
If you have a liquid sample the proper way to prepare this sample is to obtain a test
tube. To the test tube add 4-5 drops of the liquid sample. Next, add 1ml of chloroform, and
pipette up and down to mix the compounds together. Once mixed, obtain an NMR tube and
NMR cap and a small ruler preferably with the centimeters scale. Transfer the sample into the
NMR tube drop wise, and make sure the sample’s height reaches between 4-4.5 cm high
within the NMR tube. If you go above or below this measurement the NMR instrument may
have a hard time reading your sample or may not be able to lock onto your sample. Once
sample is ready take the sample to the NMR room.
**WHEN TRANSPORTTING NMR SAMPLE BE SURE IT IS TAKEN TO THE NMR ROOM VIA A
BEAKER. ALL SAMPLES SHOULD BE IN A BEAKER. TRY NOT TO TOUCH GLASS NMR TUBE
WITH YOUR FINGERS.
** Also, when labeling the NMR tube you DO NOT write on them, you a take a piece of
paper and poke a hole in it and place NMR tube thru the hole, and label the paper.
SOFTWARE: How to Set up and Prepare NMR for Analysis
1. Click on “York Chemistry”.
2. On the desktop screen click “Topspin 2.1”
The topspin 2.1 NMR software will load. There is a pink command bar at the bottom of the
screen, that it where ALL typing will be done. This bar tells/commands the instrument what
to do. Be sure to make sure your spelling everything that needs to be typed into this
command bar appropriately. Incorrect typing will not rely anything to the instrument, it will
simply not do anything for you. Also, it important to wait until the instrument has completed
your command before typing a new command. If you type too many commands at once the
instrument can get backed up and freeze or become very slow. You will know when the
instrument has completed your command because it will read below the pink command bar
“complete” or “finished”.
3. Type “ej“. This will inject the placeholder/blank sample that is always kept in the
NMR when other samples aren’t being analyzed.
There is a wooden block sitting on the computer desk near the NMR. Take the blank
sample out of the NMR and place in the black region, with blue sample holder still attached,
Monique Gray
Instrumental Analytical Chemistry
of the wooden block. Take a kem wipe and once the sample blank has been pressed the whole
way down within the block, take the kem wipe and hold around the top of the opening where
the blue hold and black region of the wooden block meet. You just want to secure the surface
so that you can gently pull out the blank NMR sample.
Pull sample out and place sample in a beaker different from your sample beaker. Take
you sample and place inside the blue tube within the wooden block. Gently, press the sample
into the blue holder until it reaches the bottom of the block and can’t go any further. This
should be done with a kem wipe. Once you have your sample in the blue holder, by the cap
take a kem wipe around your fingers and gently pull the tube out and the blue place holder
will come out with the tube. DO NOT adjust on move the blue holder because its suppose to
be in the position it is in for NMR analysis. With you other hand, take another kem wipe and
gently wipe all exposed glass and gently wipe the blue place holder.
During this whole process you should have still been hearing noise from the air
pressure at the sample injection site of the NMR. This noise is good; you’re supposed to hear
it. DO NOT inject sample if you do not hear the air pressure noise around the injection site of
the NMR. Place your sample in the same injection site that you removed the blank sample
from. The sample may seem as if it will drop into the NMR but it will float until you inject it
back into the NMR. DO NOT press down on the sample once you put it in the sample injection
whole. The sample will float until you inject the sample into the NMR.
Once sample in sample injection whole, go back to the computer and do the following.
4. Type “ ij”. This will inject your sample.
5. Type “ro on”. This will turn the spin on.
6. Type “new”. This will set up a new experiment.
- Fill in Name, Exp#, Pro#, Dir, and user from user manual on the NMR desk. It on
page 2 and is number 9.
7. In, the same window, select you solvent, “CDCL3”.
8. Select the type of NMR analysis you would want to run. (HNMR or CMHR)
9. Type “rsh” to select the shim file. (You would want to select the most recent. The
most recent is Feb 20, 2012 for your particular solvent, which should be CDCL3.
10. Type “lock”, and find your solvent. This locks on to your sample. This is how the NMR
analyzes your sample; finding locking on to the solvent that your sample is analyzed
in.
11. Type “bsmsdisp” to start shimming.
- Click on z and adjust +1 and -1 until the line has reached its max
- *If the line goes too far up the screen to where you cannot see it, click “power”
and bring the line down to where you can see it (preferably in the middle of the
center of the screen and the top of the screen, and the hit z again. If the happens
when doing z2, do the same thing but hit z2.
- Click on z2 and adjust +1 and -1 until the line has reached its max.
- Minimize screen do not exit out.
Monique Gray
Instrumental Analytical Chemistry
*** The objective of shimming it to lock onto the sample and reach the maximum point
where the NMR can view your sample. You want to have a very precise reading of your
sample so the best way to get a precise reading it to shim.
*** HOW TO SHIM: when you are ready you continue to press +/-1. You bring your line
up to where you can’t go up any further. The line will start to come down when you
reached your maximum. The point where the line starts to do the opposite of what
you’re doing, (when you’re clicking up and it starts to go down) that’s the point where
you want your line to stay.
12. Type “eda” to open experiment parameters. (You will not need to worry about this
unless you want to change the parameters, but usually you do not need to mess with
this.
13. Type “getprosol”
14. Type “rga”
15. Type “zg”
16. Type “zz” to acquire data (FOR ADVANCED USERS, but you usually can do this the
second time running a sample. For the first time using the instrument go through the
steps 13-15. Afterwards to can just type “zz”.
17. Your sample should be running now. After the sample is done running. Its time to
process the spectra.
18. Type “ft”, this does a Fourier transform
19. Type “apk”, this adjusts the phrase spectrum
20. Type “abs”, this adjusts the baseline for your spectra.
21. Integrate and pick your peaks. The best way to do this is following the instructions
manual kept in the NMR room on the desk of the computer. The integrating
instructions are on page 6-7 of the manual.
22. Print the spectra. Follow the direction in the instructions manual. These instructions
are on page 8.
23. Type “ro off”, this turns the magnetic spin off.
24. Type “ej” to eject the sample, and replace the sample with the blank sample.
25. Type “ij” to inject the blank sample back into the NMR.