Vacuum drying enables the removal of volatile solvents from a non-volatile solid or oil. This is typically carried out prior to characterisation of a compound, particularly for NMR spectroscopy, as this technique will show even trace amounts of contaminants.

These methods only remove volatile contaminants, which are usually solvents, and these steps are most commonly encountered following other purification steps such as recrystallisation or column chromatography.

There are a number of methods to acheive vacuum drying. The choice of method is dependent on the nature of the compounds to be dried and the solvent(s) being removed. Multiple methods are often used together, particularly an initial drying over vacuum to remove the bulk of the residual solvent, before switching to another method to acheive full dryness.

Drying over vacuum is suitable for solid compounds, particularly following recrystallisation. The process is a simple extension to vacuum filtration and is usually carried out as part of the vacuum filtration process. This method is effective in removing residual solvent, (particularly when present in reasonable quantities), but may require combining with another method for complete residual solvent removal.