Bruker BioSpin Solid State NMR - 4 Basic Setup Procedures

User Manual Version 002 BRUKER BIOSPIN 55 (327)
4
Basic Setup
Procedures 4
This chapter contains information and examples on how to set up basic solid-state
NMR (SSNMR) experiments. We‘ll begin with the settings for the RF-routing of
the spectrometer, some basic setup procedures for MAS probes and how to mea
-
sure their (radio frequency) RF-efficiency and RF-performance. Accurate mea-
surement of the pulse lengths and the associated RF-power levels is essential for
solid-state NMR experiments. In SSNMR, RF-field amplitudes are often ex
-
pressed as spin nutation frequencies instead of 90° pulse widths. Spin nutation
frequency n
rf
and 90° pulse width are related through the reciprocal of the 360°
pulse duration 4t
p90
such that:
n
rf
= 1/(4t
p90
)= RF-field in Hz (with t
p90
in µsec)
Setting up the magic angle, shimming a CPMAS probe, setting up cross polariza-
tion and measuring probe sensitivity for
13
C will also be explained. This is part of
probe setup and performance assessment during installation. However, regularly
scheduled performance measurements should be part of the hardware, probes
and spectrometer maintenance.
Therefore, these checks should be performed pe-
riodically.
The checks also need to be performed if an essential piece of hardware has been
exchanged. In the following, we describe all steps which are necessary to assess
performance of a CPMAS probe, along with all necessary settings. Detailed infor
-
mation about TopSpin software commands is available in the help section within
the appropriate chapter.
Setting up a CPMAS probe from scratch requires the following steps:
1. Mount the probe in the magnet and connect the RF connectors of the probe to
the appropriate preamps.
2. Connect the spinning gas connectors and the spin rate monitor cable.
3. Insert a spinner with finely ground KBr and spin at 5 kHz.
It is assumed that these operations are known. If not, please refer to the following
sources:
• Probe manual.
• MAS-II pneumatic unit manual in TopSpin/help.
• SBMAS manual in TopSpin/help.