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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 ( o4 C" k& ^5 y D& I1 U s D, ~* Y4 wof a sample, especially one which requires signal averaging or phase 9 `8 _" v: K" |7 w% `( lcycling, you need to have a temporally constant and spatially ( U: \' t; f9 c+ uhomogeneous magnetic field. Consistency of the Bo0 ]% S4 e( S9 u# x field over time will be discussed here; homogeneity will be discussed* ^! }9 K+ n9 N8 W in the next section of this chapter. The field strength might vary over" ~8 P' q: e/ _( y M5 f. s' c time due to aging of the magnet, movement of metal objects near the" p) p1 e+ P6 p9 X* m0 b' _4 M magnet, and temperature fluctuations. Here is an example of a one line6 `8 @6 L! h2 o) }. @ NMR spectrum of cyclohexane recorded while the Bo magnetic field was drifting a very significant amount.  - v/ c3 t: i0 _The field lock can compensate for these variations.

' N; ~ v7 o3 [6 I, |$ \ The field lock is a separate NMR spectrometer within your spectrometer.# F/ v% o8 |- `1 U8 W: V This spectrometer is typically tuned to the deuterium NMR resonance% n }! \1 }/ x* z) w+ [+ K frequency. It constantly monitors the resonance frequency of the 6 M1 \% M$ J# J% z' fdeuterium signal and makes minor changes in the Bo magnetic field to keep the 5 {1 r) j: S; r' n5 u) |resonance frequency constant. The deuterium signal comes from the # _( N( B9 N: X3 \deuterium solvent used to prepare the sample. The animation window ( M: r7 a' r- R contains plots of the deuterium resonance lock frequency, the small & Q2 r' G# b$ ladditional magnetic field used to correct the lock frequency, and the 8 P$ [8 a3 D9 @' Iresultant Bo - {% j$ ~' `$ A$ K. i$ afield as a function of time while the magnetic field is drifting. The 1 |4 B+ {- |# H/ N# U1 I5 \7 xlock frequency plot displays the frequency without correction. In0 ]+ A& \1 J& {, R& a4 x reality, this frequency would be kept constant by the application of 5 a' T% k& x3 c# k# |4 xthe lock field which offsets the drift.


+ t6 T# s: x4 l3 a- ?: t ; E; c' D) {4 f, W7 d, w/ N# y$ U% c4 e# o, |6 n$ d On most NMR spectrometers the deuterium lock serves a second function. It provides the =0* {' j' T1 s/ Z reference. The resonance frequency of the deuterium signal in many lock, \* V1 T W1 E* d- m2 @" r( q- I/ @. d solvents is well known. Therefore the difference in resonance frequency, Y' v6 U5 ~" f; y( s1 K/ F of the lock solvent and TMS is also known. As a consequence, TMS does! f0 N4 g% r0 T! ? not need to be added to the sample to set =0; the spectrometer can use the lock frequency to calculate : D& U+ A6 Q1 u0 c( \ q: C=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?
- m, u. C# P H# `- k

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

; Y6 p$ ~% ~ @ D1 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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