This spectrum was acquired on a 300 MHz spectrometer.
Wednesday, May 7, 2008
Simultaneous NMR of both 23Na and 51V
When one looks at an NMR spectrum, it is almost always assumed that the spectrum is composed of the resonances of only one nuclide. There are examples where this is not the case. One of these examples is shown below. The spectrum is that of sodium orthovanadate, Na3VO4 (which also forms Na2VO3(OH) in aqueous solution). The spectrum contains the resonances of both 23Na and 51V and shows the ratio between the VO43- and [VO3(OH)]2- ions.
This spectrum was acquired on a 300 MHz spectrometer.
This spectrum was acquired on a 300 MHz spectrometer.
Subscribe to:
Post Comments (Atom)
4 comments:
Dear Glen,
I don't know if you are still reading comments, especially to blog posts in 2008. But anyway....
After reading your article about detecting V51 and Na23 simultaneously, I read about V51 shifts in "NMR and the periodic table" (Harris, Mann). On page page 206 they discuss they suspicious V51-shift of [V(CO)6]- at 5662ppm. They explained this not very credible value with paramagnetic impurities. The book "Multinuclear NMR" (Mason) doesn't mention any positive V51 shift values at all (pp. 491-492) but in a table on p.492 there is a foot note "Shifts in Ref. 190 are in error".
Thanky to your post, the explanation now is obvious: The measured compund in both cases was Na[V(CO)6].
Many greetings from Germany
Martin Maurer
Dear Martin,
Thank you for the information. I’m pleased that this post has resolved a problem.
Glenn
Dear Glen,
I have found this post very useful for me to implement 23Na NMR at my current company.
Just one project that I'd like to accomplish is to replace IC for 23Na content with 23Na qNMR.
I have tested several 23Na containing compounds such as NaCl, NaF. NaI, NaBr, R-COONa, R-ONa, in known concentration confirmed by ICP.
I used ERETIC method to calculate the concentrations.
However, they all resulted in inaccurate results, off by 100-200%. they were all given d1=1, ns=32. td= 16k at 400Mhz.
Other than the sodium impurities from the NMR tubes, do you have any other thoughts that can possibly contribute to the off concentrations? I really cannot think of any other factors other than the sodium in the tubes. at the same time, wouldn't the sodium impurities be too small to make the concentration off by 200%?
I highly appreciate to this greatest NMR blog.
Jamie from Toronto
Jamie,
That is a very large error. It could be that the relaxation of all of the transitions are not the same. The outer transitions may be broader than the central transition. It could be that you are not seeing the total signal for some samples compared to others. Are all of your 23Na resonances of the same width? Are the lineshapes Lorentzian? It is also possible that you need to use a longer recycle delay. Have you tried measuring T1 relaxation times? Is the relaxation exponential in nature?
Glenn
Post a Comment