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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 * r0 V: s6 _+ r6 a. ?$ A! eof a sample, especially one which requires signal averaging or phase6 b1 S) X# {4 m, @" K( P cycling, you need to have a temporally constant and spatially" c; P5 p2 T, F- A) s homogeneous magnetic field. Consistency of the Bo! F P* B8 w7 y; O field over time will be discussed here; homogeneity will be discussed ' o) ^$ {5 T" ^ ]% h& N! I( ein the next section of this chapter. The field strength might vary over# s9 n8 D% l( q4 s E+ v time due to aging of the magnet, movement of metal objects near the / C/ r9 A0 d% lmagnet, and temperature fluctuations. Here is an example of a one line% D' b) R* d7 }" R/ n# p3 E NMR spectrum of cyclohexane recorded while the Bo magnetic field was drifting a very significant amount.  + @6 C2 T5 e7 ]! m: T The field lock can compensate for these variations.

: p% D" x: l+ yThe field lock is a separate NMR spectrometer within your spectrometer.' x3 T/ ?4 x& s7 n7 j# l This spectrometer is typically tuned to the deuterium NMR resonance 1 ]+ |. _# a* Afrequency. It constantly monitors the resonance frequency of the2 C- _, W2 X/ q deuterium signal and makes minor changes in the Bo magnetic field to keep the+ e" W' `7 |0 t7 O) e. C2 b resonance frequency constant. The deuterium signal comes from the 5 ?, h, K' `; }1 F+ W* @deuterium solvent used to prepare the sample. The animation window 5 p! v2 ]0 W" a contains plots of the deuterium resonance lock frequency, the small 9 y5 s) Q% z5 v. k% @) @6 C radditional magnetic field used to correct the lock frequency, and the/ b6 a. Y5 Y# r% t7 F- Q) R: v resultant Bo1 Y* z0 Y7 W& e$ P1 R7 [9 W field as a function of time while the magnetic field is drifting. The% C% A0 }5 A' n/ ] J% ?! ]4 x. t lock frequency plot displays the frequency without correction. In % [0 ]1 ^' x4 ^( h% N; I8 ]reality, this frequency would be kept constant by the application of & T, `5 r3 K4 Q! Z4 m8 Dthe lock field which offsets the drift.


8 s) @1 \, S- R; X% ~" @ . i) K* Y4 }0 O- O1 _: c ) B) |+ N! y0 Q! `; v& n" n+ _On most NMR spectrometers the deuterium lock serves a second function. It provides the =0 ( C* A( ]9 `2 x% areference. The resonance frequency of the deuterium signal in many lock * a! E) c8 P& ~* u9 K# f6 |( xsolvents is well known. Therefore the difference in resonance frequency& o5 a p: I! s1 h' v/ P# l1 F0 n of the lock solvent and TMS is also known. As a consequence, TMS does/ `9 d5 V! t! E/ Y* }, j5 d6 c) `# i. s1 X not need to be added to the sample to set =0; the spectrometer can use the lock frequency to calculate , C& n+ u3 G j+ ?. c8 W; A =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?
6 g: M/ n# K- G

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

1 F9 Z( s0 B% }- N: T9 k

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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