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做C13NMR谱为什么要用氘代试剂?

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发表于 2009-8-18 08:48:16 | 显示全部楼层 |阅读模式
做C13NMR谱为什么要用氘代试剂?
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发表于 2009-8-18 12:13:31 | 显示全部楼层
 需要氘代溶剂来完成锁场(Field lock)和匀场(deuterium gradient shimming).

Field Lock

In order to produce a high resolution NMR spectrum& O0 x; f* D5 V1 W6 O6 |9 Q of a sample, especially one which requires signal averaging or phase + }- {0 j/ r; {+ h! Icycling, you need to have a temporally constant and spatially- B$ o4 ~+ z1 n# k0 | homogeneous magnetic field. Consistency of the Bo 7 |/ t! P0 a& `* Ffield over time will be discussed here; homogeneity will be discussed 0 u# ]4 v3 S0 n- t/ `6 g8 nin the next section of this chapter. The field strength might vary over 3 u, o9 T) C3 X, X5 Otime due to aging of the magnet, movement of metal objects near the+ a* z, }9 N- D. L# x6 Y magnet, and temperature fluctuations. Here is an example of a one line" G% \) @5 ?/ A- ]0 P2 |$ O/ L NMR spectrum of cyclohexane recorded while the Bo magnetic field was drifting a very significant amount.  1 a% D0 Y7 B( T$ @/ IThe field lock can compensate for these variations.

. x" p8 t6 i, _+ P \# o The field lock is a separate NMR spectrometer within your spectrometer.- x5 x" Q! k6 h' i) A+ x This spectrometer is typically tuned to the deuterium NMR resonance Q/ E* H% G* _, l: O7 X3 S/ b frequency. It constantly monitors the resonance frequency of the$ T* _8 E' m+ k- Q4 x( ~ deuterium signal and makes minor changes in the Bo magnetic field to keep the2 O* H' d( Q% f6 }6 B. [. E8 e% r resonance frequency constant. The deuterium signal comes from the3 u' M' G+ x4 g5 Z deuterium solvent used to prepare the sample. The animation window  . K6 p4 u1 \8 L1 k0 R7 ^' Scontains plots of the deuterium resonance lock frequency, the small$ q w( T2 h# c! P additional magnetic field used to correct the lock frequency, and the ) L# \% t& g) \4 L/ i/ {/ presultant Bo( A6 l4 f; O* M9 O+ H+ s field as a function of time while the magnetic field is drifting. The - k. |: q% G5 l) ?# }5 W, J5 S& vlock frequency plot displays the frequency without correction. In3 q4 N, g- ]4 u" } reality, this frequency would be kept constant by the application of" i* A& y* k2 e the lock field which offsets the drift.


' d4 M$ t+ \7 X+ | $ p# E. a, K% Q2 _ 6 k8 B* n6 n$ ^1 Y4 ~% G On most NMR spectrometers the deuterium lock serves a second function. It provides the =07 y E# C) k) ]% A. t$ G/ W: _: d reference. The resonance frequency of the deuterium signal in many lock. w4 {* r8 K% S/ y3 w solvents is well known. Therefore the difference in resonance frequency . @/ m) E& Z9 W& l8 I% x' [# oof the lock solvent and TMS is also known. As a consequence, TMS does; s1 ^- b6 \4 o5 @" C8 p) [' ` not need to be added to the sample to set =0; the spectrometer can use the lock frequency to calculate : z' Z# M6 U9 {8 q=0.




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 楼主| 发表于 2009-8-18 13:34:05 | 显示全部楼层
看不懂,有中文的没?
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发表于 2009-8-18 17:25:58 | 显示全部楼层
以下是引用cannotsay在2009-8-18 13:34:05的发言:
看不懂,有中文的没?
# G' g6 T: ~6 A3 C9 p* f7 k, r

现代NMR仪器要用氘锁

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发表于 2009-9-13 15:32:24 | 显示全部楼层

楼上说的还蛮有道理的哦

4 `. r1 |, A* M: I" w4 B

超级师傅

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发表于 2009-9-16 15:59:52 | 显示全部楼层
 看看

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