Sample Preparation
Labelling of samples
Please ensure all samples brought into the NMR labs are
labelled using the tickets provided with the following details:
- Your Name
- Group or Lab Number
- Your sample reference
- Solvent
Length of NMR Tubes
Broken tubes (i.e. tubes with jagged or fractured ends) are a
potential hazard and are not
to be used. Please take any such tubes to the glass workshop where
they will grind them flat. The bottoms of tubes should be
regularly checked for hairline cracks. NMR staff will confiscate
broken NMR tubes. - Minimum tube length is 16.5cm.
- Maximum tube length for the instruments with sample changers is 22cm.
- Young's tap tubes up to
22cm long can be used on the Varian & Jeol sample
changes.
- If you have longer Young's taps tubes PLEASE CHECK WITH NMR STAFF FIRST.
Making up your samples
Sample preparation must be done in your lab, not in S100. The following procedure is recommended:- Check that the tube is clean and does not contain acetone etc. - wash with CH2Cl2 if necessary and dry under vacuum. Do not heat tubes or store them in an oven as it is likely to distort the tube.
- Check that the cap is clean and dry.
- Weigh (roughly) the quantity of sample used – >5-10mg for 1H, 20-50mg for 13C (see ‘Sensitivity Guidelines’ ). In most cases 50mg is the maximum that should ever be required. Greater amounts can result in viscous solutions which give poor resolution.
- Make up the sample in a small tube or test tube in the appropriate amount of solvent and transfer into the NMR tube – use ~0.7ml of solvent.
- Sample length should be 5cm long using 0.7ml of solvent. Shorter samples will produce spectra with much poorer resolution.
- Solid particles, especially those in cloudy solution drastically reduce spectral quality. Do not use large quantities of solvent to dissolve samples, use the minimum volume and filter (either use tissue wrapped round the end of a Pasteur pipette, or filter through a Pasteur pipette plugged with a piece of tissue).
- If your sample is unstable in air you will need to use special techniques. Consult colleagues in your research group.