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4 ADJUSTMENT OF MEASUREMENT CONDITIONS AND PROCESSING CONDITIONS
4.3
SETTING CONTACT TIME IN CP METHOD
The contact time (contact_time) is the time required to transfer the magnetization from
1
H to
13
C. The efficiency of the magnetization transfer changes depending on the length of
the transfer time. As an example, the relationship between the contact time and the signal
intensity of the
mum signal intensity occurs during 1 to 2 ms for typical organic compounds.There are
also samples that require longer contact time among samples with rapid molecular motion
(rubber and plastic crystals such as adamantane, camphor, and hexamethyl benzene) or
samples with many quaternary carbons.
Generally, the peak intensity reaches its maximum in about 1 to 2 ms for
connects directly to
NMECAXS_V50-SLD-2
13
C nucleus of polypropylene is shown in the following figure. The maxi-
0
2
Fig. 4.2 Relationship between contact time and peak intensity
1
H, and about 1 to 5 ms for a quaternary carbon.
4
6
Contact time (ms)
iso-Poly-Propylene
8
10
13
C that
4-3
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