Understanding the NMR Spectrometer

What it is, what it does and how to properly care for it

What is NMR?

Nuclear magnetic resonance is a technique used to identify molecular structures, reactions, and metabolism.  This is a common technique in drug discovery as it helps scientists who are looking to uncover specific information like structure, target binding, and confirmation preference. It is used both in the very early stages (like compound discovery) and then even later into optimization of a lead drug.

What is an NMR Spectrometer?

An NMR spectrometer is equipment that is used to perform nuclear magnetic resonance.

The NMR spectrometer consists of a superconducting magnet, a probe, a sample spinner, an RF transmitter and receiver, a shim system, a console, plus a computer and software.

The models can range in size, and capacity from some small capacity models which are roughly the size of a microwave to high-throughput models that take up an entire room and have isolation requirements.

What is it used for?

The actual process a scientist follows is sample preparation, followed by magnetic field set up, RF excitation, data analysis like chemical shift, and interpretation.

The sample which is most usually prepared with a deuterated solvent like deuterochloroform is placed into a small glass tube. This tube is inserted into a spinner that is lowered into the magnet and spun. Radiofrequency is used to generate signals that are detected and converted into a spectrum that looks like peaks. The peaks show chemical shift, splitting patterns, and nuclei which then allow the scientists to extrapolate structure.

This is useful for early stages in compound discovery when scientists are creating compounds and need to confirm their structures, find binding sites, and conformation. In drug creation most of these compounds are used to bind with a protein so knowing this information can increase and optimize binding affinity. Later down the line, once scientists want to refine their lead compound, they can use NMR to do this by improving selectivity and binding, functional group adjustments, and other refinements.

Quenching

A superconducting NMR magnet is kept at extremely low temperatures (around 4 K, or −269 °C) so the superconducting coils can carry current without resistance. If these coils warm up or the magnetic field becomes unstable, the superconductivity can suddenly “collapse.”

NMR’s require liquid nitrogen or helium to “quench” the magnet. This is a delicate process because NMRs are sensitive pieces of equipment and are very expensive. Depending on the type and size of the NMR this can mean filling multiple times a week or as little as twice a year.

Safety Precautions/ Equipment Care

Now that you understand what an important role this machine plays in R&D, let’s talk about some other important things to consider like safety precautions.

An NMR spectrometer houses an extremely strong magnetic field. Due to this anyone who has a pacemaker or any such device should not enter an NMR room as it can disrupt the pattern and cause complications. This is why you’ll see a warning sign outside of NMR rooms.

Filling the magnet has its own safety risks and considerations.

When filling the magnet, it is important to have liquid nitrogen rated plastic tubing. It is also very important to follow the correct procedure, otherwise you can blow the tubing off due to the difference in temperature when the liquid nitrogen fills the tube. This could cause liquid nitrogen to shoot out and spray into the room. Obviously, this is very dangerous as it can easily burn the skin and in extreme cases can cause a risk of asphyxiation where there is poor air flow.

One trick to limit the risk is to start the filling process very slowly at first. This allows the tube to fill with the liquid nitrogen and freeze over becoming rigid and fixed in place. Allowing the tube to adjust and slowly freeze will greatly reduce the risk of it flying off and is also better for the equipment in general.

It is also very important to wear proper protective equipment such as cryo gloves and a face shield.

Always keep track of the levels of liquid nitrogen and/or helium. These levels should be checked daily to ensure that the magnet is always full.

Conclusion

At Venture Forward Lab Partners, our personnel are rigorously trained; from being able to handle the smallest and simplest equipment to caring for something as complex as a high field NMR. We know the importance of proper procedures and maintenance. We understand how important properly running equipment is to your research.

Venture Forward Partners is a full-service Laboratory Planning, Project Management and Lab Services provider for life science and biotech laboratories in Greater Boston. From site selection and lab relocations to setting up and maintaining your lab, we provide a broad range of services and solutions to support your lab operations.  Our team possesses unparalleled energy and enthusiasm towards the work we do and we have the expertise, training, hands-on lab experience and industry connections to ensure your lab’s success.  Whatever your lab needs – we make it happen.