1 / 29

NMR SPECTROSCOPY

NMR SPECTROSCOPY. JM Franconi. 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.

lars-salinas
Download Presentation

NMR SPECTROSCOPY

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. NMR SPECTROSCOPY JM Franconi

  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 spectrum f FID

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

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

  7. 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 H1 is influenced by the 2 H2 sites Jcoupling is transported by chemical bond C C 50%(+1/2) H2 50%(-1/2) f1+dBH2 f1 f1- dBH2

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

  11. 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. 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. 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* f t True NMR resolution CONDITION: TR > DR

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

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

  18. 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. 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. 180° te/2 90° SEQUENCE SPIN ECHO SEQUENCE

  22. SEQUENCE

  23. SEQUENCE

  24. SEQUENCE DEMI TOUR!

  25. SEQUENCE

  26. SEQUENCE ECHO = coherence recovery

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

  28. 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)

More Related