1 NMR Samples Types of NMR tubes Sample preparation

2 Types of NMR Tubes Solid State Sample Rotors Solution NMR Sample Tube Spinners 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 mm

4 NMR Sample Preparation Clean clear solution Suspension or opaque solution PrecipitateNot 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

7 Good spectrum Integrals Peak picking ppm scale ppm

8 Good spectrum ppm

9 Bad spectrum ?

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

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 ppm, don’t forget to print detailed expansions.)

21 Lab Assignments Duration SpectrometerExperiment sample requirement (per 0.5 ml solution) 1.2X2 hrs MHz Comprehensive 1 H NMR + Indirect 13 C Observation100 mg 2.3 hrs 100 or 360 MHz Pulse Width Calibration and B mg 3.2X2 hrs MHz Rare spin NMRconcentrated (80-90%) 4.3 hrs360 MHz Decoupling 1 H from 13 C and B mg 5.2 hrs MHz Spin Echo and Spin/Spin Relaxation, T mg 6.2 hrs MHz Spin/Lattice Relaxation, T mg 7.3 hrs360 MHz Nuclear Overhauser Effect 25 mg 8.2 hrs360 MHz Polarization Transfer and DEPT100 mg 9.3 hrs300 MHz 13 C CP/MAS in Solids(sample provided) 10.2 hrs360 MHz HETCOR ( 1 H/ 13 C COSY)100 mg 11.2 hrs360 MHz 1 H 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.