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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 spectrum8 [& ? ~, ^3 X of a sample, especially one which requires signal averaging or phase# s8 D! \& e# u2 E( D1 r" J' W cycling, you need to have a temporally constant and spatially ' n& r& o; d: B* z! t( Thomogeneous magnetic field. Consistency of the Bo 8 s+ {) w& G% k0 |/ D7 Hfield over time will be discussed here; homogeneity will be discussed$ {" U+ M7 _3 l: ] in the next section of this chapter. The field strength might vary over ! A1 ^: p0 G* A* v& l- m5 ^/ C* j1 N$ Atime due to aging of the magnet, movement of metal objects near the % X$ @2 f# w9 u/ ]$ S, x' r% X/ lmagnet, and temperature fluctuations. Here is an example of a one line$ Y. V! ?9 y6 I1 x, C, |$ G- { NMR spectrum of cyclohexane recorded while the Bo magnetic field was drifting a very significant amount.  8 b5 l' A! x2 [The field lock can compensate for these variations.

9 I. B( b+ C B+ `$ {' v4 u1 g The field lock is a separate NMR spectrometer within your spectrometer.5 _# ^2 U# s0 x2 _$ a$ p This spectrometer is typically tuned to the deuterium NMR resonance( P* q* a* e/ i" K) W frequency. It constantly monitors the resonance frequency of the ~( Q8 c% w& f( T7 P5 z/ x! f' Y deuterium signal and makes minor changes in the Bo magnetic field to keep the" a+ j( a) E6 B v* B resonance frequency constant. The deuterium signal comes from the $ L2 C# k! }& h" ?4 k- q" N: Ydeuterium solvent used to prepare the sample. The animation window  ) M3 w2 y) h0 O# }$ F# u* f: Zcontains plots of the deuterium resonance lock frequency, the small6 C+ b( ]6 j) A7 o% |/ Y3 w additional magnetic field used to correct the lock frequency, and the 8 Y' d4 j. g( P" V1 x uresultant Bo ! J9 z1 i8 y6 F3 u* @6 l0 Ffield as a function of time while the magnetic field is drifting. The . t8 E3 d$ R0 g$ ^6 w* Alock frequency plot displays the frequency without correction. In ' {, f+ A7 g% k. c1 Freality, this frequency would be kept constant by the application of; g" [3 \/ }7 m3 f the lock field which offsets the drift.


# s, ^8 D1 T, c& N4 s 3 y, F* d8 B, C3 K : u2 @8 P# r2 {9 B8 @8 c. N. {On most NMR spectrometers the deuterium lock serves a second function. It provides the =0 2 Z" c! V$ r) O+ p S9 I( `# dreference. The resonance frequency of the deuterium signal in many lock ' {0 V7 @$ o, W# Q% csolvents is well known. Therefore the difference in resonance frequency1 w3 Y1 b' ^/ D* U+ Q8 d of the lock solvent and TMS is also known. As a consequence, TMS does 8 H' D% ^: r5 B% o2 Nnot need to be added to the sample to set =0; the spectrometer can use the lock frequency to calculate , s( t! S! d. b% K8 t( z ? =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?
4 }# W5 X! x$ ~- O

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

5 N3 f0 i3 h. K" _0 P7 G

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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