Hyperpolarization Update #6 (I hyperpolarized a thing!)

A quick recap: I’m troubleshooting a setup to do hyperpolarization, a technique that allows us to take much faster measurements of chemical samples using NMR (nuclear magnetic resonance, which uses magnets and radio pulses to give you information about chemicals, think MRI) . Hyperpolarization speeds up measurements because it increases the amount of signal you pick up from a targeted chemical, so you have to take less measurements to get the same resolution. Our technique for performing hyperpolarization involves transferring nuclear spins from parahydrogen to our sample. Parahydrogen is a spin state of hydrogen that you make at low temperatures. 

So after last week’s exciting success in finally creating parahydrogen, it was time to try doing hyperpolarization. The baseline goal of my project is to get hyperpolarization to work on small, single sided NMR instruments. However, I wanted to try to get it to work on a larger, traditional NMR instrument first, since this has been done before and allows easy separation of the targeted signals from the rest of the signals produced by the sample.

When doing hyperpolarization, it’s critical that while you are dissolving the parahydrogen in your sample, it must be in a magnetic field of about 65 Gauss. (This is what allows the polarization transfer to occur.) Luckily for me, the large NMR that I was using was unshielded, so its magnetic field extends out into the room. Magnetic field strength decreases as you move away from the magnet, so I just needed to find the right distance from the magnet that the sample needed to be held to get the correct field strength. I was able to find the position fairly easily using a gaussmeter (an instrument used to measure magnetic field strength).

My procedure to position the sample correctly is as follows: a person of my height and shoe size, wearing the converse that I usually wear, should stand with toes touching the stool in front of the NMR, then take half a step back (overestimate this step since it causes more harm to have a magnetic field that is slightly too big than to have one that is slightly too small). Finally, hold the NMR sample tube at chest height roughly a foot and a half from your body, which puts it at approximately the correct field strength. This procedure isn’t very repeatable by someone with a different height or shoe size from me, so as my PI said “if [I] get run over by a moose [the lab] is screwed.” (Not actually though, it would be trivial to locate the field again.) (But just to be safe I’ll avoid any trips to Canada.)

Anyways, after performing this procedure several times, I was able to repeatably produce hyperpolarization (see figure)! Although I have a (vague) understanding of the quantum mechanics behind this technique, it still seems like magic to see the enhanced signal.

The black line shows what the signal looks like before the sample is hyperpolarized, and the red line shows what the signal looks like after the sample is hyperpolarized. Notice that for each of the humps on the black line there is a much larger dip in the red line. (Hyperpolarization flips the sign of the signal so the bump goes down instead of up, but the important thing is that the bump is bigger.)

The black line shows what the signal looks like before the sample is hyperpolarized, and the red line shows what the signal looks like after the sample is hyperpolarized. Notice that for each of the humps on the black line there is a much larger dip in the red line. (Hyperpolarization flips the sign of the signal so the bump goes down instead of up, but the important thing is that the bump is bigger.)

I am extremely excited to start working on hyperpolarizing on the single-sided NMR! However, before I can try to get the hyperpolarization to work, I need to troubleshoot the bubbling setup we have to dissolve parahydrogen in the sample, which I suspect does not work.

Comments

  1. apleersnyder says:

    This project seems quite interesting and now it makes sense seeing you in the NMR room all the time! I was wondering more about the applications of this idea. It seems important but is there a specific application that you are moving towards? Also the way you are using the magnetic field on the unshielded NMR is a perfect use of that instrument.

  2. rabeaver says:

    Hi! Right now I don’t really have an application; my first focus was to get the hyperpolarization functional, and I didn’t know how long that would take (I was prepared to make that my entire honor’s thesis). Now that it’s working, Dr. Meldrum and I are looking for an application that will take advantage of the single-sided nature of the NMR’s that we have in our lab. We’re really excited and if you have any ideas of something we might find interesting let me know!