Correct preparation of samples for NMR measurements is essential for getting high quality NMR spectra. In order to guarantee safe operation of spectrometers and to ensure the best possible experience with our NMR instruments, please use the following guidelines:
- Never use chipped or cracked NMR tubes for your sample submission. Complaints on spectra quality will not be accepted if your sample is submitted in one of those.
- To ensure the best experience, use only the tubes provided by the NMR services. Some tubes are slightly thinner/thicker and do not fit the sample carrier. If you encounter difficulty on inserting your NMR tube into a spinner (too tight), do not force it. In case of a breakage of a tube whilst placing in a sample carrier, severe cuts to your hand can occur. Try to use another spinner or replace your tube. At the same time, make sure that the NMR tube is not loose in the spinner. If so, try to use another spinner or replace your NMR tube.
- J.-Young or any other specialised tubes can be used on our instruments, but these must be inspected and approved by the Analytical Services coordinator first. An NMR tube with a cap longer than 22.5 cm (8.5 inches) must not be used on the DEPT400 MHz instrument.
- Place your tube appropriately in the sample carrier using depth gauge. Be aware that the depth gauge is made of material that turns into a glue when in contact with chloroform or any other organic solvents. If you break your sample tube inside the depth gauge, notify Analytical Services stuff immediately and do not allow anyone to use it to avoid contamination of instrument.
- Please ensure that your compound is fully soluble in an appropriate deuterated solvent prior to placing inside the NMR tube. Optimal amount of solvent is ca. 0.6mL (for standard 5mm tube). Note, DEPT400 NMR operates at RT, that is just slightly above melting point of DMSO-d6. Consequently, fine structure of multiplets in this solvent may not be well resolved. Please, use DPX400 or DEPT500 instead, where you can setup your temperature slightly higher.
- Remember that the majority of NMR measurements require high sample concentration. If you do not get sufficient signal/noise ratio in your spectra, try to increase the concentration first. In contrast, 1H measurements require diluted samples, otherwise distortions/broadening to/of a multiplet fine structure may occur.
- Avoid attaching paper labels or anything else to NMR tubes. Parafilm tape may be wrapped around the cap to reduce solvent evaporation, a single layer of parafilm is enough. Using a permanent marker pen, a code can be written on the NMR tube, but not lower than 3 cm from the cap of the NMR tube.
- The outside of the tube must be cleaned after the sample preparation, and immediately before submission using methanol/paper tissues.
- If you break a sample tube in the NMR lab or you found that your tubes is broken after retrieval from instrument, do not leave without notifying the Analytical Services stuff. Should this happen in the absence of any staff member, e-mail the Analytical Services Coordinator immediately via email (firstname.lastname@example.org).