the samples are not completely soluble - just swelled the solvents that's mean the sample may be partially soluble
any suggestion, please
Dear Mahmoud,
Turbidity and opacity of the samples can cause problems to obtain accurate spectra, with a good noise-to-signal ratio. If you think that your sample is partially soluble, try to pulverize it (to increase the contact surface with the solvent), add the solvent, stir vigorously to get that partial solubility and then filter it before recording the NMR spectrum. Even if you have a low concentration, this can be overcome if you just accumulate the sufficient amount of scans. You can previously check if you got the partial solubility by evaporating the solvent after filtration, as a quick test (obviously, after that you can just repeat the process).
Other possible fast solution is to change the NMR solvent for another one more appropiate. There are plenty of them, even protic ones (like methanol-d4), so you can choose other more suitable for your sample.
And then you also have other non-standard options, such as derivatization of your sample so it becomes soluble or even solid state NMR if you cannot get a clear solution by any means. But these should be tested after the previous ones have failed.
Hope you find it helpful
Dear Dr. Enrique Manuel Arpa
thank you for your wonderful explanation
To assist you really need to have more info on what solvents you have tried and what solvents are compatible with your experiment. If the molecule is polar than DMSOd6 normally dissolves most small organic molecules. Can either try this on its own or as a co-solvent. If its non-polar then try to other end like CDCL3. Other solvent like D6benzene or CCL4 have been used in the past but now considered unacceptable (H&S). Sonication can help. If its a true solid like a resin then there are other specialised techniques for solid materials. Take a look at Wikipedia:
https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance_spectroscopy
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