Can I use molecular sieves to dry D2O (one of the NMR solvents)? I know that sieves are used for water removal but will it work in D2O as well?
Hi there
I'm not sure why you would want to dry D2O. I think its like trying to dry water, since D2O is heavy water. Part of the deuterium isotopes in D2O are often replaced with H particularly during NMR experiments of samples which have exchangeable hydrogen atoms hence the reason for unavoidable H2O peak in the spectra.
No I don't think you can. Molecular sieves mainly discriminate based on size (that's why you can get them with 3Å, 4Å pore size). And D2O and H2O have basically the same size.
This is a funny question. "to dry" means to remove water. How you can remove water from water?
The boiling points of H2O and D2O are different. Their separation by distillation is a common technology but with a high energy consumption.
Dear Virendrakumar, you cannot "dry" D2O. Deuterium is just another isotope of hydrogen which means that the two atoms are two sorts of the same chemical element. This is why D2O has the same chemical properties as water, i.e. chemically speaking it does not differ from normal water. The two compounds differ only in physical properties such as e.g. melting and boiling point. When we talk about drying of solvents used for NMR spectroscopy, we mean removing traces of water from organic solvents. These solvents can be miscible with water (CD3OD, acetone-d6, THF-d8 etc) or not (C6D6, toluene-d8 etc.).
Dear Virendrakumar, P.S.: As an addition to my first comment I yould like to mention that when you buy D2O for NMR measurements, this "heavy water" is more or less pure deuterium oxide, e.g. 99.9% D2O. This means that it has already been separated from normal H2O by careful distillation or electrolysis. As you know, the boiling point of "normal" water is 100 °C, while that of D2O is 101.4 °C. When large amounts of water are electrolyzed, the remained water will become enriched with D2O. For more detailed information about the technical manufacture of D2O please read the respective Wikipedia entry on "Heavy water". With best wishes, Frank Edelmann
It is not necessary to dry D2O if you buy a good quality sample from the vendors. If you keep the solvent exposed to the atmosphere for a long time, then it tends to take up the moisture from the atmosphere and results in a mixture of H2O and D2O. The best practice is to keep the solvent in a container covered with a serum cap and use a syringe with a needle to transfer. Also open the container in a glove box which will ensure that there is no contact with air and moisture. It is advisable to use 10mL vial rather than 100mL bottle since the exposure time is longer in the latter and hence more contamination.
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