Basic NMR Sample Preparation - Yale CBIC

Choose an NMR tube based on your experimental needs. Economy tubes (red cap) are basic but have poor quality control; WG1 1228 tubes are recommended for routine 400 MHz samples; higher-quality 528 PP tubes are best for extended runs, variable temperature experiments, or precious samples.

Weigh out 1-20 mg of sample material using a clean spatula. For proton spectra use 1-10 mg; for carbon spectra use as much as possible without precipitation (10-20 mg). Place the measured sample into a vial.

Add 0.6-1 mL of deuterated solvent (such as DMSO-d6 from sealed ampules or chloroform from bulk bottles) to the sample vial. Use a vortexer to rapidly dissolve all solid material until you obtain a homogeneous solution.

If solid particles remain in the dissolved sample, insert glass wool into a pipet tip to create a simple filter. Carefully pipet the sample through the glass wool filter to remove any solid particles that could degrade NMR data quality.

Using a pipet, carefully transfer the dissolved sample into a clean NMR tube, avoiding any solid particles at the bottom of the vial. Fill the tube to a height of 3-4 cm (approximately two fingers), then cap the tube.

Place the capped NMR tube into the appropriate spinner (Varian or Bruker) and insert into the depth gauge. Position the sample so the ends extend above and below the detection coil by centering on the marked center line, or push to bottom if sample is tall enough.

Wipe the outside of the NMR tube with a Kim wipe to remove fingerprints and debris. Visually inspect the sample to ensure it is homogeneous, free of particles, properly filled, and without precipitate before inserting into the NMR instrument.