It is important as sometime this was treated as reference by the Magnetic resonance instrument by default as other reference like TMS etc were absent.... From 1 of the 3 papers i come to know about the temperature dependency of the HOD PEAK already!
Based on the relative amounts of HOH and HDO, there will be a change in chemical shifts due to chemical exchange. Measuring the rate of chemical exchange at a given temperature using 1H-1H EXSY may provide additional insight.
The residual solvent signal of acetone, which should appear at 2.05 ppm can be used as a reference always as that should be unperturbed and is present in your spectra. Then you can compare the observed H2O and HDO shifts with the known values. The residual water signal in acetone normally appears at 2.84 ppm (2010-Organometallics-Fulmer article) and HDO signal at 2.80 ppm.
But Acetone-d6 is one of the most expensive NMR solvent! Right? Also it's not easily available!
Another issue is inclusion complex of cyclodextrin is quite less soluble in CDCl3....
Acetone d-6 is one of the cheapest NMR solvents- its price is usually lower than DMSOd-6 or highly enriched D2O. Ask your supplier about it.
Acetone d6 is not used very often because of its reactivity, not because of the price.
But generally-it is not the best idea to use HOD signal as a reference if very accurate values of chemical shifts are needed, as its exact position, shape and intensity are rather unstable.
There are multiple (better) ways to reference the NMR spectrum.
Yes of course, but in our field the solubility of the prepared inclusion complex is less in chloroform ( Most cases insoluble) so chances of using CDCl3 as solvent is not there. But thanks for your suggestions
I'm not sure why CDCl3 ?
1) You can chose from at least 10 common deuterated solvents with resonable price.
If you can not change the solvent:
2) you can add a reference compound to your sample.
If you don't want to add anything to your sample:
3) you can use an insert (coaxial tube or capilary) with anything you want to use as an reference.
If you don't like anything form 1-3:
4) You can use external reference technique- this one is a litle bit tricky, but in theory you can pick up any NMR tube found in the room with anything in it and reference your spectrum on it.
There are many solutions for NMR spectrum calibration and you should choose the one that suits best your sample.
Cheers!
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