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NMR equipment is expensive, yet delicate, especially the NMR probehead, which is inside the magnet. While the automated operation excludes many of the steps that may cause damage, the users must still follow a certain protocol when preparing and submitting their samples and avoid improvising in unfamiliar situations. Please read the following before attending NMR training session. Usually, you will be trained to use the 300, 400 and 500 MHz instruments first. Once experienced, you will be allowed to use the 600 and 700 MHz instruments.
Safety
NMR magnets are permanently active and are independent of electricity supply. Make sure you do not carry any ferromagnetic object, such as keys, scissors, paper clips or a screwdriver, either in your hands or in your pockets when approaching magnets in the NMR lab. Your phone and mobile devices such as a tablet or a USB stick, as well as bank and travel cards, can be damaged by NMR magnets and should, therefore, be left on the table between the old fridge and the printer or in the office area.
If you see a staff member or somebody else filling NMR magnets with liquid nitrogen or liquid helium, do not approach or speak to them. Skin contact with liquid nitrogen (temperature -196 oC) or liquid helium (temperature -269 oC) can cause tissue freezing resulting in severe burns and you must avoid approaching magnets during cryogen fills or distract those working with cryogens.
Your Sample
To avoid instrument downtime, never use chipped or cracked NMR tubes. NMR tubes of the standard length are available from the stores. An NMR tube with a cap longer than 22.5 cm must not be used on the 400 MHz NMR. Long J Young tubes (~23 cm in length) are no longer allowed on any of our NMRs. Short J Young tubes must be used on 400 and 500 MHz instruments.
Avoid attaching paper labels or anything else to NMR tubes. Parafilm may be wrapped around the cap but only a single layer of parafilm should be used. A paper label or a thick layer of parafilm near the top of the NMR tube may lead to misalignment of the tube when picked by the sample changer. This would lead to a broken tube near the entrance into the magnet thus damaging the equipment.
The outer surface of the tube must be cleaned after the sample preparation. Using a marker pen, a short code (e.g. ABC18, where ABC are the user's initials) can be written at the top of the NMR tube, not lower than 3 cm from the cap of the NMR tube.
If you encounter difficulty when inserting your NMR tube into a spinner (too tight), do not force it. Use another spinner. At the same time, you need to make sure that the NMR tube does not slide up and down too easily in the spinner. If it does, use another spinner or a spinner with two black O-rings at the bottom. If the tube still slides too easily in the spinner, replace your NMR tube.
If you break a sample tube in the NMR lab, do not leave without notifying the NMR manager. Should this happen in the absence of the staff member, e-mail the NMR manager immediately (a.e.aliev@ucl.ac.uk). The depth gauge is made of a material that turns into a glue-like material when in contact with chloroform or other organic solvents. If you break your sample tube with an organic solvent inside the depth gauge, notify the NMR manager immediately. In his absence, you must ensure that the damaged depth gauge is not used for tube depth adjustments. This is to avoid the transfer of contamination into the probehead inside the magnet. In the absence of the NMR manager, a damaged depth gauge or a spinner with broken glass inside it must be left on the sample preparation desk near the solid-state NMR instrument.