Chapter 2. CP/MAS Solids Operation
37
VNMR 6.1C User Guide: Solid-State NMR 01-999162-00 C0402
6. Enter crossp=dipolar cntct=2500 at=0.02 d1=1 nt=4 sw=45000 .
7. Set the following parameter values according to the spectrometer used.
8. Enter lb=50 ga.
9. When acquisition is finished, enter dssh to display the results.
10. Select the spectrum with the lowest value of tpwrm that gives the maximum signal
and set tpwrm to the value of this spectrum.
11. Optimize pw.
a. Array pw from 0 to 2 times its current value.
b. Enter d1=1 ga.
c. When acquisition is finished, enter dssh to display the results.
d. Select the spectrum with the maximum signal and set pw to this value.
e. Enter ga.
f. Save this spectrum for reference.
12. Continue with “Measuring Signal to Noise,” page 37.
Measuring Signal to Noise
1. Use the parameters and the value of tpwrm from “Adjusting the Hartmann-Hahn
Match,” page 36.
2. Enter d1=5 nt=4.
3. Enter ga.
4. Set delta=10000 and place cursor at the right edge of the spectrum and enter
dnsmax to measure the signal to noise.
5. Compare the signal to noise to the specifications.
If necessary, increase the gain and repeat step 2 through step 4. Do not overload the
ADC.
6. Repeat step 2 and step 4 three times and record the signal to noise for each test.
7. Record the average signal to noise for the system.
2.8 Referencing a Solids Spectrum
A solids probe is not locked during operation. If exact chemical shifts are required, a
spectrum of a test sample with know chemical shift must be obtained. The HMB
signal-to-noise sample can be used for this purpose.
1. Obtain a spectrum of HMB using the parameters that gave the best spectrum in 2.7
“Calibrating the CP/MAS Probe,” page 35.
2. Enter cr=100p movetof.
Parameter INOVAcpmas
INOVAcpmas
(1 kW amplifier)
MERCURYcpmas
gain 40 40 20
tpwr 60 54 63
tpwrm array(‘tpwrm’,40,95,100) array(‘tpwrm’,52,0,5)
To Next Page
Loading...
