Vacuum evaporation

Vacuum concentrators use a combination of heat, vacuum and centrifugal force for the evaporation of volatile samples. The method is used for evaporation, drying, purification and especially fast concentration. It takes advantage of the fact at pressures of a few hectopascal, volatile substances boil at room temperature without freezing the specimen.

The additional centrifugal force from rotation prevents bumping and changes the liquid level in the test tubes, thereby increasing the evaporation surface. The applied heat increases the rate of evaporation without causing overheating of the specimens under vacuum. Rotational Vacuum Concentrators (RVC) are an alternative to the following methods:

• Distillation systems and rotary evaporators use high temperatures for evaporation and operate at nearly atmospheric pressure or vacuum levels down to approximately 100 mbar.
• Freeze drying systems operate at very low temperatures and high vacuum down to less than 0.01 mbar. Although sublimation preserves the specimens, it is time consuming, and not all solvents are suitable for freeze drying.

Rotational vacuum concentration occupies a position between the two methods mentioned above. With suitable parameter settings, the resulting products can also be frozen and sublimated in a sort of final-drying process.

The boiling point for liquid evaporation depends on the nature of the substance concerned and the external pressure. Reducing the pressure dramatically reduces the boiling point of the solvent and therefore avoids overheating of samples.

The rotary vacuum concentration is characterised by the following features

• No foaming of the samples, minimal loss
• Numerous samples can be dried simultaneously
• Concentration of the samples at the bottom or wall of the vessel, particularly advantageous for small volumes or thin solutions
• Suitable for drying aqueous and highly solvent-containing samples
• For volumes smaller than 1 ml up to 3 litres
• Reproducible drying processes through controlled process parameters such as rotor temperature and vacuum
• End of drying can be estimated by measuring sample temperature and/or pressure rise
• Simple and safe solvent recovery

1. Analytical applications

2. Molecular biology applications / Life sciences