1. NMR SPECTROSCOPY
JM Franconi 1

2. MR SPECTROCOPY
Principle of FT NMR spectroscopy
In a spectrum, each signal represent the resonance frequency
of a nucleus in a specific environment
Bo is fixed
a RF pulse irradiate a broad range of frequency RF
irradiation
sampling FT t
FID
spectrum f

3. MR SPECTROCOPY
Non selective RF pulse
In spectroscopy the RF pulse used is < 100 microsecond RF
rectangular
sinc
g.B1 > 2pF
F frequency range

4. RF pulse Magnetisation evolution
MR SPECTROCOPY
RF pulse Magnetisation evolution
During RF pulse M rotate
Around x direction with an angle: Bo z
Q = g. t . B1 q Mz M y O
Mxy x

5. MR SPECTROCOPY
spectrum parameter
chemical shift f f1 f2 f3 f4
A same nucleus can have different resonance frequency

6. chemical shift phenomenon
MR SPECTROCOPY
chemical shift phenomenon Bo Bo
Bo1 H2
Bo2 H1 O C
Bo2
Bo1

7. chemical shift measurement
MR SPECTROCOPY
chemical shift measurement
u i
u ref
reference f
paramagnetic
low field
high electronégativity
Diamagnetic
High field
Low electronégativity

8. MR SPECTROCOPY
J coupling
J coupling is an interaction between close nuclei
This interaction is independant of Bo field
It does not exit on one isolated molecule
JAB fA fB f

9. MR SPECTROCOPY J scalar coupling H1 C C 50%(+1/2) H2 50%(-1/2) f1+dBH2
H1 is influenced by the 2 H2 sites
Jcoupling is transported by chemical bond C C
50%(+1/2) H2
50%(-1/2) f1
f1+dBH2
f1- dBH2

10. MR SPECTROCOPY
J dipolar coupling
Coupling is also possible directly through space r H1 H2
1/r6

11. The Nuclei magneticaly equivalent have the same chemical
MR SPECTROCOPY
J coupling
The Nuclei magneticaly equivalent have the same chemical
shift. They do not show any coupling effect Ha C
fHa = fHb = fHc C Hb Hc

12. The componants relative intensity are given by a binomial
MR SPECTROCOPY
J coupling
Rules for multiplicity determination
A I nucleus coupled to n spin S give a signal with:
2.n.S + 1 componants
The componants relative intensity are given by a binomial
Distribution.

13. MR SPECTROCOPY
Signal area
NMR spectroscopy is a quantitative method f

14. Concept of digital resolution
MR SPECTROCOPY
spectrum quality DR
Concept of digital resolution
AT = N.DW DW t f At
R = 1/AT
Digital resolution FT
Frequency domain
Time domain
T2*
TR=1/pT2* t f
True NMR resolution
CONDITION: TR > DR

15. MR SPECTROCOPY
Sampling rules
Application of Nquist theorem DW f1 f2 f2 f1 f2
F=1/Dw
2. F. Aq = N

16. The gyromagnetic ratio and the natural isotopic abundance
MR SPECTROCOPY
Sensitivity
The gyromagnetic ratio and the natural isotopic abundance
determine the NMR signal available
- the nucleus sensitivity is proportional to Bo2 and g3

17. concept of population and coherence
MR SPECTROCOPY
concept of population and coherence Mz Mz
MR signal E2 RF E2 E1 E1
population
Cohérence=transition

18. Polarisation transfer (NOE)
MR SPECTROCOPY
Polarisation transfer (NOE) C
+1/2
-1/2-1/2
Transition C13 C
-1/2+1/2
+1/2
Long
distance
+1/2 H
Transition H1
Niveau C13
+1/2-1/2
-1/2
+1/2+1/2 H
Niveau H1
2 independant level of energy
system of 4 levels of energy
NO COUPLING
COUPLING

19. Polarisation transfer (NOE)
MR SPECTROCOPY
Polarisation transfer (NOE)
dH = 4.dC f f +5
-dH-dC
+dH-dC
C13 transition
-dH+dC
H1 transition
dH-dC
-dH-dC -3
-dH+dC
dH+dC
POLARISATION
H1 TRANSITION SATURATION

20. SEQUENCE

21. SEQUENCE
SPIN ECHO SEQUENCE
90°
180°
te/2

22. SEQUENCE

23. SEQUENCE

24. SEQUENCE
DEMI TOUR!

25. SEQUENCE

26. SEQUENCE
ECHO = coherence recovery

27. SEQUENCE SPIN ECHO 90 o
180 o
FID
ECHO DE SPIN T2
T2*
Mxy t

28. CONCEPT OF PULSE SEQUENCE
SPIN ECHO SEQUENCE
180°
90° TR TE RF GS GP
DAC on GR
CONCEPT OF PULSE SEQUENCE

29. NMR SPECTROSCOPY APPLICATION
Chemical structure determination (protein, ADN,…)
Quantitative measurement
(isotopic enhancement determination)
food and beverage quality control
Spectroscopy in vivo (metabolism caracterisation)