I wanted to study structural /functional group changes of a compound at alkaline buffer (pH 12). But for buffers, salts and NaOH used will have hydrogen in them. So the solvent peak will mask all the compound peaks. How can this problem be solved?
Are there other techniques apart from NMR that can be done?
You can try selective spin polarisation transfer based NMR pulse sequences, there are several such methodologies available in NMR pulse sequence design and analysis literature, i suggest you consult an NMR expert in this regard, he/she can point out the best pulse sequence suited to your problem.
Is it a problem with a little bit of water in your samples? There is always a bit of water and for most purposes it is not a problem.
You need to prepare your buffer by dissolving the relevant salt(s) in D20. To adjust the pH you can use a solution of solid NaOH dissolved in D20. That is the procedure I have used to create buffered D20 solutions with a minimum of hydrogen present.
Thank you Schonbeck. For NMR, I will have to prepare everything in D2O. Water peak suppression can be done to suppress the peak due to little amount of moisture. But, I was concerned about the Hydrogen in the salts used for buffer preparations, like NaH2PO4, H2PO4 or even NaOH. Since the salts concentrations will be in millimolar range, the aqueous salt peak will dominate.
Sanjana Skumar You are right that the water peak will be larger than any onther peak as the concentration of hydrogen will probably be on the order of 100 mM (depending on your buffer concentration). But is that a problem? Even in good quality D20 there is hydrogen present, especially if the bottle has been opened and closed many times. A large water peak is not necessarily a problem. Only if the peaks of interest a located close to the resonance of HOD there might be a problem.
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