Nuclear Magnetic Resonance Spectroscopy (NMR)

Why NMR? The most powerful and broadly applicable technique for structure determination Provides the most information about molecular structure 1H NMR and 13C NMR are the most common

NMR in Peer Reviewed Papers

What is NMR? Applying an external magnetic field

How is the External Magnetic Field Created? It is created by a superconducting electromagnet

The NMR magnet is a coiled wire Made of nobium and tin/titanium Lots of current is running through it

Your sample is placed in the middle of a magnetic field The lower the resistivity the higher the current The higher the current the stronger the magnetic field

How do we achieve low resistivity? The wire needs to be at supercritical temperature This is extremely cold If the wire goes below its supercritical temperature it has 0 resistivity

Nobium Niobium makes for a terrific superconductor It has a high critical temperature compared to other elements on the periodic table at 9.25K

That means at that temperature its resistivity is exactly zero It can handle lots of current to increase magnetic field strength  Nb is bonded with tin or titanium (to make Nb3Sn or NbTi wire) to increase durability

Liquid Helium The magnet sits in the coldest substance on the planet Liquid Helium is 4K Liquid Nitrogen (77K) keeps this cold The air conditioner (65 °C) keeps the LN2 cold

Safety Rules Do not turn off the air conditioner Wear a sweat shirt If He rapidly boils it will throw the magnet off center This is a QUENCH! QUENCH = BAD A quench repair on average is $18,000 Cost of NMR $350,000 - $800,000

NMR Probe It’s “pulse” NMR because the console generates RF pulses orthogonally to the magnetic field The probe delivers and receives them to produce a signal Tune properly..but be careful with Tune and Match Rods (use red non-magnetic tool to turn) http://www.analyticalspectroscopy.net/

Let’s run a sample https://youtu.be/B_NWbcDVhMk

Quick Tips to Preserve Probe Use the spacer tool LFG - LISTEN FOR GAS when sample is at top of bore Document all error messages Try “ii restart” if you can’t wobb or lock Try another “getprosol” if you can’t wobb or lock If it’s not the machine it’s probably your sample (Is it the solvent? Is it fresh? Is the sample at optimal concentration?)

Quality Control Prevention is the best medicine Refurbished probe New Console New Software Record error messages (led to updated firmware) Write name on schedule If you see something say something (24/7)

Quick Tips on NMR Tubes Wilmad 528-pp, 8 inch Putting in oven too long can….. ….warp the glass

THINK: What can the NMR do for YOU?