NMR Sample Preparation notes:

Best practices: 

• 1-5mg for Proton;  5-30mg for Carbon and other heteronuclei.
• Use clean and dry glassware.
• No undissolved material should go in the NMR tube. (No Floaters)
• Dissolve sample in separate vial then transfer to the NMR tube by pipette. 
• Sample + Solvent height 40mm in the NMR tube.
• Dry NMR tubes under N2, not in an oven.

Notes:

• Samples that are too concentrated can among other things be difficult (if not impossible) to shim. A sample that is too dilute are just that... too dilute.  20 mmol is a good upper limit for Carbon, much less for Proton
• X(grams)=(0.02moles/liter)(MWgrams/mole)(0.0007liter) 
• No floaters! If there are suspended particulates in the sample, filter it!
• Check the NMR tube for straightness (economy tubes are easily bent in drying ovens and sometimes come bent right out of the package)

Watch the videos:

1 minute Video on making and loading an NMR sample

3 minute Video on making and loading an NMR sample