Do-it-yourself NMR spectroscopy

[Simon Quellen Field]

Slightly different from the MRI topic, so I changed the subject line.

I sell extremely strong magnets (1.48 Tesla NdFeB, 52 MegaGaussOersteds).

They can be arranged as a Hallbach array to get closer to 2 Teslas.

NMR spectroscopy is done with magnets in the 1 to 10 Tesla range.

The stronger the magnet, the stronger the signal, but a 1 Tesla magnet

would still provide a signal strong enough for a sensitive receiver.

Such a receiver is in the off-the-shelf television tuners that plug into a

standard PC bus.  There is a lot of Linux software for dealing with these,

and making things like spectrum analyzers.

So the idea is this:  Build a small tabletop NMR spectrograph using an

array of Neodymium Iron Boron supermagnets, and a television tuner

in a Linux box.

Typically, NMR spectrographs use a constant frequency and vary the strength

of the magnet.  With permanent magnets, we would sweep the frequency

and keep the magnetic field strength constant.  Or we could use the pulse

technique and do an FFT of the resulting signal (that requires a more

powerful transmitter, but these are available to those of us with amateur

radio licenses).

"http://www.cem.msu.edu/~reusch/VirtualText/Spectrpy/nmr/nmr1.htm"

"http://electron9.phys.utk.edu/phys250/modules/module%203/nmr.htm"

"http://en.wikipedia.org/wiki/Halbach_array"

"http://iopscience.iop.org/0031-9155/34/9/013;jsessionid=F6204DD0CB5E13C4F4EEEA73A88D1F62.c2"

"http://www.sbf1.sbfisica.org.br/eventos/enfmc/xxv/programa/res0411.pdf"

"http://www.springerlink.com/content/f513765r513w6t8x/"

"http://www.teachspin.com/newsletters/08-4%20SeptPS2.pdf"

I can have the magnets manufactured in any shape or size required.

But I suspect the 12 mm cubes I already carry will do just fine.

On Tue, Mar 16, 2010 at 2:52 PM, Brent Neal <bre...@gmail.com> wrote:

On Tue, Mar 16, 2010 at 15:25, Cathal Garvey <cathal...@gmail.com> wrote:
> Of late, I have fretted along similar lines that patents have stifled the
> development of MRIs. How old is that technology? Why hasn't it been
> developed into a benchtop device by now that we can use for in-vivo live
> imaging? These things have remained huge, room-filling beasts that are only
> used for one task, and I imagine the blame for that lies with the patent
> holders.
>
> Of course, I'll happily admit that this is speculative complaining. With
> regard to the original article, I agree wholly; some disciplines are
> initially colonised by experts but get standardised and black-boxed down to
> amateur level. Others, mostly the ones that are overregulated or patent
> stifled, remain needlessly difficult and remain the purview of the
> "Experts".

There are many good reasons why live-human MRIs remain relatively
controlled. The first is the necessity of and potential side-effects
of the contrast agents. The second is the need to handle liquid
helium. Any moron can be reasonably safe with liquid nitrogen - except
for the morons who think they can drink it. Handling liquid helium
safely is a -whole- different ballgame.

I wouldn't worry so much about this needing a distributed approach at
this juncture. The economic incentive to reduce the cost of labor for
these is profound - its just not that apparent in the US.  Way On Back
When, I did a project where we were designing expert systems for
"upgrading" the types of work that a nurse radiologist could do, thus
reducing the cost of the so-called experts immensely.  One issue with
deploying those systems in the US is the AMA, who can effectively
lobby to prevent them from being used without the supervision of an
Appropriately Licensed Professional (i.e. an MD.)  That's the real
culprit here, not the patent system. (the first MRI was developed in
the 70's. The key patents will have long expired on that. Even some of
the second-gen patents will have probably either expired or become
long in the tooth.)

B


--
Brent Neal, Ph.D.
http://brentn.freeshell.org

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[Ron Amundson]

A few comments

DIYing a probe (coil assembly and sample holder) small enough for a
12mm magnet might prove near impossible. Decades ago, my magnets pole
pieces were around 100mm, and my probe assembly was only 15mm long by
5mm diameter. Granted, technology has changed multifold since then
with much more sensitive and lower noise electronics, but probe size /
field uniformity are still issues.

I think using the TV tuner card to capture the ~63Mhz time domain
signals could prove pretty difficult as well, and thats apart from the
issue of RF leakage during the transmitter on time overloading the
receiver, combined with a the unknown overload recovery aspects of
said tuners.

NMR system design is tricky, and all sorts of voodoo events seem to
pop up out of nowhere... Mr Maxwell is always right, but alas one is
not always aware of where and when what fields and other effects and
such may occur.

That being said, if one were to take a series of smaller steps,
perhaps starting out with earths field NMR and the vastly simpler
hardware (audio sound cards come to mind) might prove a lot less
headache prone.

[Simon Quellen Field]

If it was too easy it wouldn't be fun.

At 1.48 Tesla, shouldn't the frequency be closer to 200 MHz?

The tuners are good for 54 MHz to 1002 MHz.

With the CW method, we are looking for a peak or dip in the response as the

frequency scans through a range.  The receiver would be attenuated until the

signal did not saturate, so it would be operating in its normal range.

We can make the magnets any size of shape we need -- they are not the expensive

part (that would be the transmitter or the computer, but some of us already have

those lying around).  But it is also easy to attach each Hallbach array to a 6 inch

disk of sheet steel as a pole piece to get a larger area if needed.  But a gram of

sample doesn't need that much room.

[Ed]

I am a student, and I could certainly know more about the topic of how nmrs are manufactured, but I wanted to add that it can be done tiny, one could potentially 3d print most of the metal or plastic parts of the probe and have the glass mount thingy made (is it easy to make precise glass bits? I don't know.) I would love to make one of these. Check out picospin. They made an 82Mhz nmr the size of a shoebox that uses a 2T magnet. The similarly sized 45mhz one that they make costs $25k (maybe more or less now, they got bought by thermoscientific) according to a powerpoint presentation I saw on it. I realize this is an old discussion, did anything come of it?

[buzda2]

Hi!

Another student here :-)

Where can I find the presentation you are referring to?

Thanks,

[Nathan McCorkle]

Thanks for reviving this thread, ed! I've got one of the $20 Linux tv receivers, and some magnets I think might be NIB!

On Mar 3, 2014 7:28 AM, "Ed" <ebon...@gmail.com> wrote:

I am a student, and I could certainly know more about the topic of how nmrs are manufactured, but I wanted to add that it can be done tiny, one could potentially 3d print most of the metal or plastic parts of the probe and have the glass mount thingy made (is it easy to make precise glass bits? I don't know.) I would love to make one of these. Check out picospin. They made an 82Mhz nmr the size of a shoebox that uses a 2T magnet. The similarly sized 45mhz one that they make costs $25k (maybe more or less now, they got bought by thermoscientific) according to a powerpoint presentation I saw on it. I realize this is an old discussion, did anything come of it?

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[Jonathan BISSON]

Nathan McCorkle <nmz...@gmail.com> writes:

> Thanks for reviving this thread, ed! I've got one of the $20 Linux tv
> receivers, and some magnets I think might be NIB!
> On Mar 3, 2014 7:28 AM, "Ed" <ebon...@gmail.com> wrote:
>

Don't mess with DVR receivers, you will need real amps, filters for
that. The NMR signal are really small, you can't be close to a computer
to receive them. At least you will have to preamp before sending to your
receiver if you really want to use it (but then you will have delay and
phase issues but let's keep that for later).

Did you see these links ?
http://www.conspiracyoflight.com/NMR/NMR.html
http://kuchem.kyoto-u.ac.jp/bun/indiv/takezo/opencorenmr/

[spencer whyte]

Hey, another student here. I have been working on my own DIY NMR on a budget for a little while now.

Nathan is right, when operating at low fields it is a constant fight against noise.

The best article I have seen so far is this one:

http://iopscience.iop.org/0957-0233/21/10/105902

It is an absolute must read if you are interested in constructing your own NMR on a budget.

All the best,

Spencer Whyte

[Jonathan BISSON]

spencer whyte <spence...@gmail.com> writes:

> Hey, another student here. I have been working on my own DIY NMR on a
> budget for a little while now.
>
> Nathan is right, when operating at low fields it is a constant fight
> against noise.
>
> The best article I have seen so far is this one:
>
> http://iopscience.iop.org/0957-0233/21/10/105902
>
> It is an absolute must read if you are interested in constructing your own
> NMR on a budget.
>
> All the best,
>
> Spencer Whyte
>
>

Hi,

You will need to take care of what you are looking for. Which kind of
samples do you want to analyze ?

The chemical shift dispersion is dependant of the field. So on
ultra-low-fields, you will not be able to distinguish different
compounds (at least not all their signals) and you will be overflooded
by higher-order effects and the influence of coupling constants (which
are everything but negligible at these fields).

I'm pretty impressed by the S/N quality of their spectrums, well ok they
used 0.5L of sample ;) but still, with such cheap amplifiers that's a
good result.

Their technology is pretty nice and can be improved a lot. Especially
decoupling the computer from the acquisition, you can use better cards
than arduinos and connect sdcards for storing acquisitions. Then you can
run your system completely in a faraday cage, avoid those main (50 or 60
Hz and their artifacts) and CFLs (ahh those crappy little emitting
things…)

If you need to develop a complete system you have these :
http://store.gadgetfactory.net/papilio-one-250k/
(This one is just an example, there is a lot of FPGA cards out there)
They will need a lot of development, but having an autonomous system is
priceless in these conditions and you will not be limited anymore by
limitations of an arduino.

Hmmm now I want to build one :p

[Josiah Zayner]

Detecting 1H(especially water) in NMR is the easy peasy thing because it is sooo abundant(99.98% 1H). People first detected water using NMR in the 1940s.50s? Other spin 1/2 nuclei however are not so abundant (C13 = ~1% and N15 = ~0.4%). What this means is that you either need a sample that is huge(liters) or pure and highly concentrated(> 20mM) or you need 15N 13C isotopes which are $$$$$$. Detecting these signals, say carbon splitting can be difficult for modern spectrometers(>=10 Tesla) on anything but very simple molecules not to mention water signal suppression as water will overtake your spectra, shiming to create an even magnetic field, and as people have said signal to noise.

The OpenNMR says they use a superconducting magnet which cannot run at room temperature(at least I don't know of any room temperature super conductors). Usually to make a material super conducting you need to drop the temperature down to < 10K using liquid helium with a liquid nitrogen barrier to prevent rapid evaporation of the helium. These liquids are not cheap. Also, when using electromagnets field inhomogeneities can become an issue. Then you need D2O($$$) for signal locking for frequency drifts. Many detection coils nowadays are also at cryo temps to reduce electronic noise.

It seems like a cool hobby but realistically it doesn't seem very plausible to create a spectrometer that can do much more then detect water DIY. There is a reason somewhat besides price gouging that modern spectrometers cost in the millions of $$$$.

During my Ph.D. I used NMR extensively(Varian and Bruker) and took care of the NMR spectrometers ((500MHz and 600Mhz Varian) usually NMR spectrometers are referred to by their 1H resonance frequency not their magnetic field strength(I don't know why?) so I don't know the Tesla) at University of Chicago for a bit so I know a little but I am by far no expert just an NMR user.

Josiah