158 (327) BRUKER BIOSPIN User Manual Version 002
REDOR
Packing the sample is critical for the success of the experiment, check your sam-
ple is within the central region of the spinner or use a 12ml spinner. The quality of
the refocusing p pulses is essential, this can only be achieved with a center
packed sample. The coil of a 4mm MAS probe has a length of 10 mm, the sample
should be no longer than 5mm, preferably 3mm (CRAMPS spinner or 12 ml HR-
MAS spinner).
Setup the CP conditions for the
1
H magnetization transfer on both coupled nuclei
(X and Y). Use cp90 to determine precise p pulses on both the X and Y channel of
your probe.
Accurately setup the p/2 and p pulses for both
13
C and
15
N according to the stan-
dard setup procedures with an accuracy of at least 0.1ms.
After the setup, the pulse lengths for the different channels should be within the
same duration and short enough to not exceed an overall duty cycle of about 5%.
One can reoptimise the refocusing pulse on the coupled nucleus using a 1D ver-
sion of redor, setting the number of experiments (1 td) to 1. Here, the number of
refocusing pulses l0 is chosen to a value in a way that there is a noticeable de-
crease in dephasing experiment (normally this is between l0=1-15), and then the
refocusing p pulse is optimized for minimum signal intensity in the dephasing ex-
periment.
Table 12.1. Acquisition Parameters for a
13
C observed C/N REDOR
Parameter Value Comments
pulse program cpredori pulse program
nuc1
13
C nucleus for f1 channel
nuc2
1
H nucleus for f2 channel
nuc3
15
N Nucleus for f3 channel
p3 according to specs π/2 pulse on f2 channel
p15 2000 Contact time between f1 and f2
pcpd2 about 2*p3 pulse length for decoupling sequence
p2 according to specs, 6-10 µsec π pulse on f1
p12 about 10 µsec π pulse on f3
cnst31 =masr MAS spinning rate
l0 1 starting value for the desired evolution time,
value must be odd
d1 4s recycle delay
pl1 for HH condition f1 power level for contact pulse
pl11 according to specs f1 power level for π pulse
sp0 for HH condition power level for
1
H ramp
pl2 - not used
To Next Page
Loading...