Generally it depends on the nature of compounds – are they organic compounds or biological samples (proteins, oligonucleotides, etc.), and their stability. In my opinion, in most cases dry storage is preferable. First, water can react with many compounds (as well as some other solvents), so it is better to avoid it. Second, the flexibility of molecules and the rate of their movement are minimal in solid state, so dry storage decreases the reaction rate for both intra- and intermolecular processes. This is one of the reasons to avid the storage in any solvent. Third, some compounds can react with oxygen dissolved in water – in this case, if you still want to store your compound in a solution, you have to use degassed water. As to biological molecules, it is not so easy. Of course, proteins and nucleic acids, especially RNA, are not very stable in water. On the other hand, many proteins that were obtained in solution after drying will not dissolve again easily. There is one more issue with macromolecules – freezing/thawing may lead to the cleavage of their chains (and this is the practical method for that)

Hi! MyungJo Kim,

Generally, we will go for neat compound storage. The Neat storage is the prefered way to store compound. Storing in solution of some organic solvent won't affect the compound's nature provided your compound is stable enough. If the solvent not affecting your compound's stability means why one should go for solution storage process.

If your compound having stability problem, that time you can store with the solvent that stabilizes your compound (best example: BF3 in ether, Grignard Reagents in THF, NaH in mineral oil).

Finally, the storing procedure is based on your compound's basic physical and chemical nature..........Best Wishes............ 

Generally it depends on the nature of compounds – are they organic compounds or biological samples (proteins, oligonucleotides, etc.), and their stability. In my opinion, in most cases dry storage is preferable. First, water can react with many compounds (as well as some other solvents), so it is better to avoid it. Second, the flexibility of molecules and the rate of their movement are minimal in solid state, so dry storage decreases the reaction rate for both intra- and intermolecular processes. This is one of the reasons to avid the storage in any solvent. Third, some compounds can react with oxygen dissolved in water – in this case, if you still want to store your compound in a solution, you have to use degassed water. As to biological molecules, it is not so easy. Of course, proteins and nucleic acids, especially RNA, are not very stable in water. On the other hand, many proteins that were obtained in solution after drying will not dissolve again easily. There is one more issue with macromolecules – freezing/thawing may lead to the cleavage of their chains (and this is the practical method for that)

I think this is an interesting question.

I agree with some of the other researchers in this thread claiming that storing samples neat in fridge/freezer provides the best stability. If I suspect that my compounds are reactive, I usually keep them under argon in for example a Schlenk flask and also wrap the flask in some foil to keep light out.

However, with some few compounds I have found that neat storage severely facilitates decomposition. In these cases I have actually kept them under some good quality pentane (insoluble), which prolonged the shelf-life with many weeks. I do not know if this method is used in general, but it worked pretty well for me:)

Neat/dry is probably the best way to store a reactive solid for reasons already explained in posts above. Some highly reactive liquids are best stored as a solution in benzene, which is then frozen to reduce mobility.

Apart from what has been mentioned; one way to overcome storage difficulties for biological samples or macromolecules in water is to flash freeze them with liquid dimethyl ether. This prevent the formation of ice crystals and the amorphous ice has a similar density profile to water that preserves structure. It should then be stored in a low temperature freezer (-78°C is common)

Fridges and freezers can be annoying due to condensation, particularly for some common use chemicals. For long term storage it's great but most sensitive chemicals I tend to use immediately or prepare as needed.