Dear Mr. Sinclair,

if your compounds are uniform it should be possible to do some NMR experiments on them using a sensitive spectrometer, e. g. one with a cryo probehead. You could obtain one-dimensional 1H-NMR spectra without problems and also, by indirect detection, two-dimensional heteronuclear correlated spectra like 1H,13C-HSQC or -HMBC spectra. If possible, one should not use (deuterated) methanol as the solvent because one would lose information on the presence of exchangeable protons (OH, NH, SH).

Best wishes.

Hi Mr. Sinclair,

I agree with Mr. Ernst, a 400 MHz or 700 MHz NMR apparatus would give you a 13C NMR and enough 2D-NMR Spectra to help with complete characterization. You could expect it  to take a few days to complete all of the NMR experiments depending on the molecular weight of the pure samples and the NMR apparatus available. 

Best wishes with your experiments! 

I entirely agree with L. Ernst and D. Delannoy.

Good luck

It depends on the number of protons per mole or per gram really but I have done full characterisations of natural products at 400 Mhz on about 500 mg of sample but agree with the previous authors - you need indirect detection for the 2Ds and it  will take at least overnight for these to achieve reasonable resolution.

If you have NMR with cryo probe head 

Definitely you can get good spectrum

Good luck

there are NMR tube that are very thin, so you can use minimum solvent and get higher concentration

good luck

 Dear Mr. Sinclair,

Dr. Ernst gave you good advise. Also note his comment about solvents - protic solvents like deuterated methanol will result in exchange of OH, NH, NH2, SH protons if present in your compound; those resonances will diminish or disappear, and you will loose important information. Also, use dry solvent! Dry DMSO-d6 is often a good solvent, owing to H-bonding property it often moves OH and NH proton resonances downfield (to higher frequency) out of the more crowded regions of the 1H spectrum.

Good luck in your research - AF

Thank you so much everyone. Thank you Mr Ernst and Mr Foris for the solvent advice. I've read that DMSO-d6 has a few disadvantages in NMR also I know it's never easy to get back your compound when dissolved in it, therefore I am not sure if it will be used. I will be sending my samples to our collaborators for analysis and will update on the progress.

Thanks again.

James

Dear James, I agree when 0.8 mg are the world's supply of a new compound it is better to use a solvent that is easily removed such as MeOD. You r collaborators should start with 1H, HSQC and HMBC. Do you have high res MS? Knowing the mocelular formula goes a long way together with NMR to elucidate the structure.

Dear James,

Yes, all solvents have advantages as well as disadvantages. The choice of solvent depends on the solubility of the compound, the desired information, what possible loss of information is acceptable, as well as the ease of sample retrieval. When only a very small sample is available, careful consideration of the choice of solvent is mandatory.

A trade-off is often necessary. Best of luck in your research.  

Dear James,

• with our 500 MHz, cryo, 1.7 mm machine we often can do a de-novo structure determination on 10 ug within one weekend exp. time for a MW
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Dear James, 

If you have access to equipment as described by Dr. Ross (11.7T spectrometer with 1.7 mm cryoprobe), you should be able to do your structure determination over a weekend. But even at a somewhat lower field (e.g., 9.4T) with a cryo-probe, you should be able to do it. 

As early as 1979, at DuPont's Jackson Laboratory, using a 1.7 mm insert with a Varian XL-100-15/TT CW/FT system we were able to obtain some useful information on very small samples in dry DMSO-d6. Today's much more modern, high-field spectrometers equipped with cryo-probes offer very high sensitivity and facilitate complete structure identification as described by Dr. Ernst. 

Good luck in your research

Tony

interesting