Decoupling Techniques
User Manual Version 002 BRUKER BIOSPIN 91 (327)
SPINAL Decoupling 5.1.3
SPINAL provides adequate decoupling bandwidth even for high field (>400 MHz)
instruments at an RF-level of 80 kHz or higher. SPINAL-64 (64 phase permutati
-
ons) outperforms TPPM and may be used as standard decoupling sequence. SPI-
NAL-64 can be optimized in the same way as TPPM, by incrementing pcpd2 (p31)
(the phase shifts are fixed). The decoupling pulse is an approximate 180° pulse.
Reference:
1. B.M. Fung, A.K. Khitrin, K. Ermolaev, J. Magn. Reson. 142, 97-101 (2000).
Swept-Frequency-TPPM 5.1.4
This decoupling method combines TPPM and a frequency variation via. pulse
length variation to achieve a wider decoupling bandwidth. The decoupling efficien
-
cy is better than TPPM (especially at high fields), and comparable to if not better
than SPINAL-64. The corresponding cpd-program is called swftppm.
Reference:
1. R.S. Thakur, N. D. Kurur, and P. K. Madhu, J. Magn. Res. 193, 77 (2008).
XiX Decoupling 5.1.5
XiX decoupling requires high spinning speeds, but decouples at a moderate RF
level. 180° proton pulses are used, synchronized to the rotor speed such that re
-
coupling does not occur (pcpd2≠n/4*rotor periods). Usually, pcpd2 is selected to
be about 1/3 rotor period. The decoupler power level must be adjusted to produce
a 180° pulse of (rotor period)/3.
Reference:
1. A. Detken, E. H. Hardy, M. Ernst, and B. H. Meier, Chem. Phys. Lett. 356, 298-304 (2002).
Pi-Pulse Decoupling 5.1.6
Pi−pulse decoupling is a decoupling program, for weaker nuclear interactions like
J couplings or weak dipolar interactions, using rotor synchronized 180° pulses. π-
pulse decoupling uses the xy-16 phase cycle for large bandwidth. Abundant pro
-
tons cannot be sufficiently decoupled with this method, but it is very suitable to re-
move couplings to
31
P, which is hard to do by cw or tppm, since the chemical shift
range is wide. Likewise, it can be used to decouple dilute spins or spins which are
homonuclear decoupled by spinning (
19
F).
Reference:
1. S.-F. Liu and K. Schmidt-Rohr, Macromolecules 34, 8416-8418 (2001).
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