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Welcome to the Tips, Videos and Knowledge Base page, where all our tutorial videos can be found.  Beneath the video list are some tips and tricks to help you with your NMR analysis, followed by our new knowledge base where some of the more common questions we receive are answered.

NMR Service Tutorial Videos

These short (2-3 minutes) training videos will cover most of the common problems and questions we encounter on a daily basis.  We recommend downloading the video to your computer or device and playing it from there for best performance.  All videos are in .avi format.  Please send any questions or queries about these videos to the NMR Service team at nmr@ch.cam.ac.uk.

  • Video Tutorial 002 - Filling in a Sample Submission Form - Filling in a Submission Form.avi Slightly out of date as we have changed to online submission only due to the COVID-19 pandemic, and redesigned the form slightly, but the essence of the information given is the same.
  • Video Tutorial 003 - Preparing your NMR Service sample in a 5mm NMR tube - Preparing your sample in a 5mm tube.avi

NMR Service Tips and Tricks

Here are some tips and tricks to make your life easier and solve some of the common problems encountered when submitting samples to the NMR Service or using one of the spectrometers.

Preparing your sampleNow available as a video tutorial (see above) When making up your sample try to avoid floating impurities or other solid material in your NMR tube.  These will affect the quality of your spectrum.  If necessary, filter your solution before putting it in the NMR tube.  Aim to get about 0.7ml of solution in your NMR tube.  The individual vials of solvents that the NMR Service sell are 0.75ml, sufficient for one sample at the correct depth in the tube.  Too little solvent means that the air-liquid boundary may fall in the area of the probe coils leading to field inhomogeneity.  Too much solvent means your sample concentration is lowered leading to a requirement for a longer acquisition time.

NMR tubes - Your NMR tubes should be straight, free from scratches, and a minimum of 17.5cm in length.  This will mean that you can use your tube in any of the systems with a sample changer.  Short tubes may fail to be picked up by the sample changer, which could stop the automatic run.  You should always use Wilmad 528PP tubes in the departmental spectrometers - other makes of tube may slide too easily in the spinners, break more readily and not be manufactured to such fine tolerances leading to inhomogeneity and poor spectra.  The NMR Service reserve the right to remove any non-standard tubes from the open-access spectrometers.  You should take care when placing a cap on your tube, especially if the top of the tube is chipped.  We sometimes have second-hand Wilmad 528PP tubes for sale at half the normal price - please ask in B28.  Tubes that have been gathered from the open-access spectrometer rooms and have gone uncollected for two weeks are available on a first-come first-served basis, usually from 8am on Tuesday mornings.

Inserting your tube into a spinner - You should take care when you insert a tube into a spinner (turbine).  Grip the tube towards the bottom and gently insert into the spinner.  Do not exert too much force - you may find that rotating the tube as you push it helps.  Keep your hand near to the spinner as you push the tube further into it.  Gripping the tube at the top and attempting to insert it into a spinner can create unnecessary forces which may cause the tube to snap with the potential for injury.  When using a ceramic spinner for variable temperature work you should take extra care as they tend to be tighter than the normal spinners.

Breakages - We are all human, and sometimes things go wrong.  If you break a tube in an NMR room, please try and clean up as much as possible, collecting the broken glass and disposing of it in a safe manner.  If you break a tube when it is in a spinner, please bring the spinner to the NMR Service in B28.  We have a tool for removing the glass from the spinner, and can clean it and return it to service.  Please do not throw the spinners away - they are very expensive to replace.  If a tube breaks inside the magnet, you should stop work immediately and inform the NMR Service.  If this occurs outside normal working hours, then you should leave a large note on the instrument to warn others not to use it.  Please email or leave a note for us - we will endeavour to clean inside the magnet and probe and restore the instrument to service as quickly as possible.

At the spectrometer - When you have inserted your sample into the magnet it is good practice to load the default shimset.  The previous user of the instrument may have been working with an unusual sample and the shims may be a long way from their default position.  This could make your sample difficult to lock and shim.  Type rsh and select the shimset named current or similar.  This will provide a good starting point for shimming your sample with Topshim.  You should not assume that the probe is tuned correctly either.  Check the tuning using atma (or by typing wobb and manually adjusting the knobs on the underside of the probe on non ATM equipped probes).  If you have any problems with locking and shimming your sample, or tuning the probe then please see us in B28 as we will be able to help you get the best possible result.

Variable temperature NMR - When running experiments at very high or low temperatures you should use a ceramic spinner.  You should also use the bore gas system which helps maintain the bore and o-rings in the magnet nearer to room temperature.  This is operated from the top of the magnet.  Please see the NMR staff in B28 if you do not know how this works.  You should use the default configuration files when changing between temperatures, as these have heater power and gas flow calibrated.  If you need a different temperature, select the nearest temperature file, and just change to the exact temperature required manually.  The BBO Smart Probe 500MHz spectrometer (Glengrant) has a BCU chiller unit that can lower the temperature to -80C - controlled as normal using the edte window. The old style chiller units will lower the temperature to -5C, below this you will need to use the liquid Nitrogen tank and apparatus (with compatible probes).  See the NMR Staff if you have not used this before.  When using the TCI 500 spectrometer (Glenlivet), please be aware of the upper temperature limit of the probe which is 45C.  Increasing the temperature beyond this limit will trigger the Cryoprobe to warm itself up, thus ruining your experiment.  Please allow extra time to return the probe to the default temperature when booking slots on the instruments.  For sessions of a number of hours at elevated or lowered temperature, it could take up to 30 minutes to re-equilibrate at the default temperature.

Filling in a submission form - Now available as a video tutorial (see above) - The sample submission form (available on the NMR Home page) helps us decide on the length of experiments we will run.  Please take a little time to fill it in accurately and correctly.  The sample weight and molecular weight of your sample are the most important pieces of information.  The difference between 2mg and 0.5mg could be the difference between hundreds and many thousands of scans for a carbon experiment.  If you don't know the exact molecular weight then make a very rough calculation to the nearest hundred.  Don't forget to fill in your solvent details - we don't like having to sniff your tube to find out what it is!  Try to write clearly, especially your name, telephone number and email address - we sometimes need to contact you before running your sample.  Your personal code should relate to an entry in your lab book, and this is what we will name the experimental files prefixed by your group initials.  For example jrn-abc1-25-prep.  Please include the structure if you know it, it does help us to decide if the NMR experiment is successful or otherwise.

Salty (Ionic) samples - These types of samples often cause problems when they are very ionic. In cryoprobes especially they can be difficult to tune and result in broader peaks. To counter this you can move the sample further away from the NMR coils. This is achieved by using a 3 or 4mm tube and the special spinners available from B28. By using the same amount of sample with the reduced volume of solvent you can increase the number of nuclear spins in the active volume thus helping to claw back some of the sensitivity lost by having the sample further away from the coils.

3mm Match set

Topspin installation and use - TopSpin 4.x is now free for academic use.  For information and assistance with this software please see our home page. We have an installation guide for TopSpin 4.x and Duncan has also written a guide to processing using TopSpin which is very informative.

 

NMR Facility Knowledge Base

In this new section of our website we aim to answer some of the common questions that we receive in person and by email on a regular basis as each new intake of researchers get to grips with NMR.

1. How the heck do these Accuratus keyboards work??

2. How do you use this booking system? How can I set one up?

3. Quantitative NMR - a quick overview

 

 

Our new Accuratus glass keyboards are fantastic for sanitising in the current COVID-19 climate, but they can be a little tricky to get used to. Firstly there is a quick instruction guide put together by Duncan available here. Secondly there are a few tricks to getting it to work when it appears to have given up the ghost, usually as a consequence of someone poking the wrong key or button!!

Symptom: Nothing happens.......

Are the lights on? If not, try each of these in turn until something does!!

  • Push 'Wake'
  •  Check the keyboard isn't locked. If it is, hold the 'Lock' button for 3 seconds until it unlocks
  • Turn the keyboard power on with the power switch at the back
  •  Plug the white USB-C cable into the back of the keyboard

The lights are on, but nothing happens

  • Toggle the connection to '2.4'
  • Plug the USB cable in and toggle to USB

Symptom:  The mouse doesn't work

  • Toggle the trackpad to on

All the controls can be found in the PDF guide link above.

 

 

Clustermarket Manuals and Guides are all available at their website and the link is here!

It is quite intuitive to use as a basic booking system but if you are setting it up for a large facility with different groups of users with different training records and different requirements it does take a little learning. Don't learn on the job like Andrew, just download the manual.....yes

 

Questions about using NMR quantitatively crop up all the time! Duncan has a pretty stock standard answer which serves as a quick overview of the perils and pitfalls of relying on your NMR spectrum to give a quantitative answer!

All NMR is precisely quantitative, as long as you understand the spin system sufficiently well! So the books will tell you for the relative integrals within a spectrum to be correct, you need to wait 5 x the longest T1 between each scan (for a 90 degree pulse). The absolute integral ratios should scale between samples, so twice the concentration would give twice the absolute area, as long as you do exactly the same experiment. In other words the same number of scans, the same receiver gain, delays, temperature etc. However as this is essentially a physics experiment, your chemistry might spoil it!! What we mean by this is; as the properies of a solution change they affect things like the efficiency of the receiver coils, or a decoupling sequence may interfere with the area of the peaks of a 19F spectrum if the protons are particularly close. If you want to quantify a known substance you can run a range of concentration with a defined experiment to give you a calibration curve. Duncan has  even done quantitation of 13C labeled glucose and lactate in brain microdialysates by using test samples and ignoring all the trouble of relaxation delays and 1H-13C nOe effects. So we'd give the same advice to anyone wanting to use NMR to quantify samples. Please do test the methodology with known test samples first!