Varian UNITY INOVA NMR, Hardware Installation

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Chapter 6. CRAMPS/Multipulse Module Tests
56
UNITY
INOVA Solids Hardware Installation 01-999044-00 C0501
Finally, set
phase2=0
and repeat the
pw90
determination as outlined above, using the
flip-flip process. No reexamination of gating is required, but the 90° pulse should be set as
precisely as possible.
Using MREV8 to Demonstrate Multipulse Operation
The MREV8 pulse sequence demonstrates the operation of the multipulse system.
1. Enter
mrev8
to set up the sequence and parameters for the MREV8 pulse sequence.
2. Make sure that
tau=3.5
,
rof1=1.5
, and
rof2=0
.
3. Enter
go
. A FID should be obtained.
If the FID is off-resonance, enter
gf
or
acqi
and adjust the probe tune/match to
place the FID on-resonance.
4. Array
tof
from –1e4 to 1e4 in 1000 Hz steps.
5. Set
d1=20
and enter
ga
.
The resultant displayed spectra should show a single resonance that moves with
tof
. Note that changing
tof
by 1000 Hz does not move the peak by 1000 Hz!
6. Write down the value of
tof
that gives the sharpest line. This is a guide for later use
of the multipulse sequences.
Testing
1
H Wideline
The
1
H wideline test is more of a proof statement than a test with a quantitative result.
1. Use adipic acid as the sample. If using a CRAMPS probe, pack a rotor as detailed in
“Preparing the Sample” on page 56 for the CRAMPS probe tests. If using a wideline
probe, pack a 15 mm long piece of 5 mm NMR tube with about 3 mm in depth of
adipic acid. Try to arrange this so that when placed in the probe, it is approximately
in the center of the coil.
2. Install the probe and sample in the magnet. Do not retune the probe.
3. Change the following parameters from those used for the MREV8 test:
seqfil='s2pul' np=1e4 tof=0 nt=4 cp='y' d1=40 lp=0 rp=0
lb=250 ga
4. When the experiment is finished, compare the resulting spectrum with Figure 28
The spectra should be similar. The lower trace of the wideline
1
H spectrum in Figure
28 is 2 MHz wide. The upper trace is an expansion showing the shape of the line.
Testing the CRAMPS Probe
Follow the two procedures in this section only if you are installing a Varian probe.
Preparing the Sample
The final tests are performed using a solid sample of adipic acid. This compound is a white
powder. Sample preparation is crucial to obtaining the resolution specification. The sample
must be packed centrally in the rotor and must be only 1 mm long; this is done as shown in
the following steps.
1. Pack either a spacer or some inert material with no protons to the center of the rotor.