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21.3 Testing Decoupler 90° Pulse Width with Polarization Transfer
2.
Retrieve an appropriate parameter set (assuming that dpwr or dhp is set correctly)
by entering rtp('/vnmr/tests/gamah2')
3.
Acquire two spectra by entering ga
4.
Display the first spectrum with two cursors by entering ds(1)
5.
Position the cursors on the
outer lines of the triplet, as
shown in Figure 25.
6.
Read the value delta from
the screen. Divide the result by
2 (because we really want just
the value of a single splitting)
and write down that number.
7.
Display the second spectrum
by entering ds(2)
8.
Position the cursors in a similar
fashion, and read the value of
delta. Again write down half
that difference.
9.
Figure 25. Measuring Residual
Couplings in Dioxane
Start the program to calculate the strength of the decoupler field by entering:
h2cal.
When the system prompts for the low-field residual coupling value, enter the result
from step 6.
When the system prompts for the high-field residual coupling, enter the result from
step 8.
When the system prompts for the full coupling constant, enter 142, the value for
dioxane.
The system displays the calculated value of the decoupler field strength γH2, the
predicted coalescence point (the frequency at which single-frequency decoupling
would collapse the dioxane to a singlet), and the pulse width for decoupler pulses if
this decoupler level is to be used for pulsed decoupling.
21.3 Testing Decoupler 90° Pulse Width with Polarization Transfer
Sample: 30% menthol in CDCl3 (Part No. 00-968120-94)
Parameter set: /vnmr/stdpar/C13
The decoupler 90° pulse width value (parameter pp) from the test above should be
appropriate for polarization transfer experiments. It is also possible to calibrate pp
separately by using a polarization transfer pulse sequence directly, on the sample of
interest. As an example of this procedure, a sample such as menthol having CH, CH2 and
CH3 carbons is useful. If menthol is unavailable, use any small molecule organic compound
that is highly soluble.
1.
Enter jexp2 setup('C13','CDCl3') nt=4 ga.
2.
Phase the spectrum and place the two cursors around the aliphatic region.
3.
Enter movesw ga to narrow the spectral window. Phase the new, narrowed
spectrum.
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