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NMR Samples

NMR Samples. Types of NMR tubes Sample preparation. Types of NMR Tubes. Solution NMR Sample Tube Spinners. Solid State Sample Rotors. NMR Sample Tubes with Caps. NMR Sample Preparation. Use clean + dry NMR tubes and caps (tubes can be re-used, caps should not!)

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NMR Samples

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  1. NMR Samples • Types of NMR tubes • Sample preparation

  2. Types of NMR Tubes Solution NMR Sample Tube Spinners Solid State Sample Rotors NMR Sample Tubes with Caps

  3. NMR Sample Preparation • Use clean + dry NMR tubes and caps (tubes can be re-used, caps should not!) • 0.5 ml deuterated solvent (i.e. CDCl ,C D , acetone-d ,etc.) • substrate requirements for routine spectra: 10 mg for proton NMR 100 mg for carbon-13 NMR • min. filling height of tube: 2 inches (5 cm) • Cleaning of tubes: 1. rinse with solvent you were using 2. rinse with acetone 3. dry in (vacuum-)oven at low temperature 5 mm 3 6 6 6

  4. NMR Sample Preparation Clean clear solution Suspension or opaque solution Precipitate Not enough solvent Two phases Concentration gradient GOOD! B a d S a m p l e s !

  5. Good and bad NMR Spectra … are the result of: • Sample preparation • Choice of solvent • Homogeneity of magnetic field • Data acquisition parameters • Processing procedures

  6. Good spectrum ppm ppm

  7. Good spectrum ppm Peakpicking Integrals ppm ppm scale

  8. Good spectrum ppm ppm

  9. Bad spectrum ?

  10. Bad spectrum ! No units specified for axis and peak picking Signal/Noise ratio bad

  11. Bad spectrum ?

  12. Bad spectrum ! Tall signals are cut off

  13. Bad spectrum ?

  14. Bad spectrum ! Signals too small (only allowed to compare signal intensities between different spectra)

  15. Bad spectrum ?

  16. Bad spectrum ! Broad signals(bad sample, poor shimming, wrong processing parameters)

  17. Bad spectrum ?

  18. Bad spectrum ! Signals are distorted (automatic phase correction is often insufficient) Excessive peak picking (low p.p. threshold,also due to improper phasing)

  19. Bad spectrum ?

  20. Bad spectrum ? Areas without signals should be excluded. (If you want to print all your spectra with a default range, i.e. 0-10 ppm, don’t forget to print detailed expansions.)

  21. Lab Assignments Duration Spectrometer Experiment sample requirement (per 0.5 ml solution) 1. 2X2 hrs 100 + 360 MHz Comprehensive 1H NMR + Indirect 13C Observation 100 mg 2. 3 hrs 100 or 360 MHz Pulse Width Calibration and B1 100 mg 3. 2X2 hrs 100 + 360 MHz Rare spin NMR concentrated (80-90%) 4. 3 hrs 360 MHz Decoupling 1H from 13C and B2 100 mg 5. 2 hrs 100 + 300 MHz Spin Echo and Spin/Spin Relaxation, T2 100 mg 6. 2 hrs 100 + 300 MHz Spin/Lattice Relaxation, T1 100 mg 7. 3 hrs 360 MHz Nuclear Overhauser Effect 25 mg 8. 2 hrs 360 MHz Polarization Transfer and DEPT 100 mg 9. 3 hrs 300 MHz 13C CP/MAS in Solids (sample provided) 10. 2 hrs 360 MHz HETCOR (1H/13C COSY) 100 mg 11. 2 hrs 360 MHz 1H COSY / NOESY (optional) 25 mg Use your own samples, if possible. Familiarize yourselves with the procedures for each experiment, before you come to the lab. Print the manuals.

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