The overwhelming consensus is that it's difficult to impossible,
especially at natural abundance. It appears that the chemical shift
range is less than the expected linewidth, and the sensitivity is
very bad. A few people gave useful references to published studies
and some seem so have had success with solid state NMR. Apparently
there is great interest in this for characterization of rubber. I
have listed all of the responses below with incriminating information
removed. Many thanks to all who responded, hopefully I can dissuade
the faculty in question from using NMR for this.
QUERY: I have been asked about the possibility of using 33S NMR for
characterization of polymers with strings of S-S-S-S... in the
polymer backbone. It looks like an uphill battle: spin 3/2, low
freq., low abundance. But I wondered if anyone has ever tried
this. I think mass spectr. would be a better tool.
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RESPONSES:
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RAMAN.
We tried S33 NMR on [neat] DMSO and that did not even work.
Hopefully someone from the Univ of Akron (OH) will respond to this
post. When I was a grad student there it seemed there was an effort
to look at 33S of polymers. Sorry but I do not recall how successful
it was. I do agree another method would be superior than NMR. Good
luck finding a useful spectrum.
and very broad lines when not symmetric....
Horrible idea. Linewidths would be much bigger than chemical shift
variations.
Sorry for the tongue in cheek comment, but it smells like an uphill battle
to me. Without symmetry the S-33 signal would kill you whether by solid or
liquid high res NMR.
Since I am a person who works with TD NMR I thought you may have wanted a
slightly different approach that is rapid, reproducible and non-destructive
all at once.
Rubber manufacturers who vulcanize rubbers uses low resolution TD NMR to
study their polymer structures via Proton NMR. They measure structural
ratios as a function of temperature. You can distinguish S-S cross linking
and strand mobility since T1 and T2 features of these polymers which are
dramatically different by at least an order of magnitude.
NIR or FTIR may give a better handle on your structure than MS. What type
of prep work do you need to run these compounds by MS? Usually the prep
sometimes kills the structure information.
I was recently asked to do 33S also, and it turns out that the BBFO ATM
probe on my new AV-III 300 can actually tune to 33S (I don't have any other
low-gamma probes here). I was able to see natural abundance 33S
using a saturated ammonium sulfate solution, but this post-doc will have to
use 33S enriched materials to make this work for real. Of course, if I
could go higher than 23MHz it would help :o). The quad-moment is very
small, much smaller than 27Al and on the same order as 11B, which we do all
the time... even in automation on the 300.
I tried to observe 33S in liquids a couple of times in the distant past. As I
recall, no signal was ever found on compounds of interest. The large
quadrupole moment is probably resulting in enormous linewidth. Probe ringdown
most likely is also a problem, probably requiring a pulse sequence to
reduce/eliminate it.
This is not to say that it is impossible, some people have done it. Jim Hinton
at U of Arkansas in Fayetteville studied 33S way back when. You might want to
check his work, in particular, "Sulfur 33 NMR Spectroscopy" in Annual
Reports on NMR Spectroscopy, Volume 19, 1987.
Others have used Solids MAS, I never attempted that myself.
I tried doing S33 once and you're right. It's a steeply uphill battle.
I worked on 33S NMR as a graduate student. A graduate student before
me had vulcanized rubber samples made using enriched 33S.
Unfortunately, I could never find the procedure he used to make the
samples and never felt comfortable publishing the results. Below is a
copy and paste of what was written up at the time. The signal I
observed was real and not probe ringing. Had we received funding for
the project I would have loved to pursue it. I acquired the spectrum
on a 750MHz instrument, I think 10kHz MAS, and hundreds of thousands
of scans. The recycle delay was very short. I could probably dig up
the raw data if you want it. Several years ago you could get S-33,
elem., enrichment 99.9%, 1000 mg at the price of 12.00$/mg from Gamma
Lab Development out of Russia. I would not even attempt 33S NMR on a
polymer sample if it wasn't labeled. Also even with the labeling, if
the sample is crystalline/rigid with no symmetry around the sulfur
nuclei the large QCC will kill your chances of seeing something.
difficult. search Jack Koenig. he has done something.
We have done this experiment a number of years ago. With S-33 (50%)
labeling, signal averaging for days, and a 750 Mhz spectrometer we
saw something that looked hopeful, but not quite good enough to publish.
In 1987, I managed to do this for sodium dodecyl sulphate and manged
to get some results. I was only a PhD student then but the
expereiemnt required an excessive number of scans. All details are
ost but memory tells me it worked. I manged to distinguish between
the H0 and H3 phase transiton of micelles. Recently (last year) we
have made many compounds wih multiple -S-S- bonds and electrospray
works well (Synthesis of MBT). Hope this helps.
I suspect you would be wasting your time - the sensitivity is lousy
and the variation in chemical shift would probably be significantly
less than the linewidth (a bit like trying to characterize peptides
using O-17). However, if you want to dig around it a bit have a look
at the attached article and then try a citation search on it. (J.
Chem. Soc., Faraday Trans. 2, 1985, 81, 63-75)
Neil E. Jacobsen, Ph.D.
NMR Facility Manager
Department of Chemistry
119 Old Chemistry
1306 E. University
University of Arizona
Tucson, AZ 85721
520-621-8146
FAX 520-621-8407
Received on Tue Feb 16 2010 - 08:35:34 MST