Basic Setup Procedures
User Manual Version 002 BRUKER BIOSPIN 75 (327)
For optimum shims (rarely required) set the shims x, y, z
2
, xy and x
2
-y
2
, as well as
xz and yz. You may need to increase the acquisition time aq to see the effect of
increasing resolution. Save the shims using the command wsh followed by a suit
-
able name.
Before the shims are saved, it is recommended to reset the field value in the
bsmsdisp menu to be exactly on resonance with your shift reference sample of
choice (protons of adamantane or water in D
2
O or silicon rubber).
This allows the command probefield (TopSpin version 3 and up) to set the field
according to probe shims and magnet drift (see below, and
"Field Setting and
Shift Calibration" on page 87).
Note: For long acquisition times (aq > 0.05 s) the decoupling power level pl12
must be set to +3 dB and d1 must be increased to 6s. To allow longer acquisition
times than 50 msec, the ZGoption –Dlacq must be set in ased, if the pulse pro
-
gram contains the include file aq_prot.incl. Make sure the –Dlacq option is not left
set for the following steps.
Calibrating Chemical Shifts on Adamantane 4.5
In TOPSPIN (as well as in the XWIN-NMR 3.5 release) the frequency list for NMR
nuclei follows the IUPAC recommendations (see: R.K. Harris, E.D. Becker, S.M.
Cabral de Menezes, R. Goodfellow and P. Granger, NMR Nomenclature. Nuclear
Spin Properties and conventions for Chemical Shifts, Pure Appl. Chem. Vol. 73,
1795-1818 (2001) for reference).
Set the
13
C low field signal of adamantane to 38.48 ppm. This will set the param-
eter SR which is used to calculate the chemical shift axis and the peak positions in
the spectrum.
Note: All data sets generated from this data set will have the peak positions cor-
rectly calibrated, if the magnetic field B
0
is not changed. However, you must make
sure that the magnetic field is always the same. It may change, if the magnet has
a slight drift, or if different shim settings are loaded. Therefore the same shim file
should be loaded and the field be set to the same value using the BSMSDISP
command. If the magnet drift is noticeable, the calibration should be redone in
suitable intervals and the field value recorded in the lab notebook.
One can also use a spinner filled with H
2
O to set the field position more precisely.
Do not spin the sample and make sure the cap is well fitted. Set o1p to 4.85 ppm,
set for proton observe (as described above for adamantane), and use gs for con
-
tinuous pulsing and FID display. Change the field value in bsmsdisp until the FID
is exactly on resonance. Then all spectra taken should be correctly referenced
with sr = 0. For more information on correct field setting and shift calibration, see
"Field Setting and Shift Calibration" on page 87.
For all these experiments the field sweep must be off! When the BSMS unit is
turned off and on again, the sweep will always be on. Running spectra with the
sweep on will superimpose spectra at different fields! One can set the sweep am
-
plitude to 0 in order to avoid such an accidental error condition.
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