A rotary evaporator (or rotavap/rotovap) is actually a device used in chemical laboratories for the effective and gentle removal of solvents from samples by evaporation. When referenced in the chemistry research literature, description of using this technique and equipment may include the phrase “rotary evaporator”, though use is often rather signaled by other language (e.g., “the sample was evaporated under reduced pressure”).
Rotary evaporators can also be utilized in molecular cooking for your preparation of distillates and extracts. A rotary evaporators for sale was introduced by Lyman C. Craig. It was first commercialized by the Swiss company Büchi in 1957. Other common evaporator brands are EYELA, Heidolph, IKA, KNF, LabFirst, LabTech, Hydrion Scientific, SENCO, Shanghai HJ Lab Instruments, and Stuart Equipment. In research the most frequent form is the 1L bench-top unit, whereas large scale (e.g., 20L-50L) versions are employed in pilot plants in commercial chemical operations.
A motor unit that rotates the evaporation flask or vial containing the user’s sample.
A vapor duct this is the axis for sample rotation, and is also a vacuum-tight conduit for your vapor being drawn off the sample.
A vacuum system, to substantially lessen the pressure within the evaporator system.
A heated fluid bath (generally water) to heat the sample.
A condenser with either a coil passing coolant, or a “cold finger” into which coolant mixtures such as dry ice and acetone are placed.
A condensate-collecting flask in the bottom from the condenser, to capture the distilling solvent after it re-condenses.
A mechanical or motorized mechanism to quickly lift the evaporation flask through the heating bath.
The rotovap parts used with rotary evaporators could be as simple being a water aspirator having a trap immersed in a cold bath (for non-toxic solvents), or as complex as a regulated mechanical vacuum pump with refrigerated trap. Glassware utilized in the vapor stream and condenser may be simple or complex, depending upon the goals in the evaporation, and any propensities the dissolved compounds might give the mixture (e.g., to foam or “bump”). Commercial instruments can be purchased including the fundamental features, as well as other traps are made to insert between the evaporation flask and also the vapor duct. Modern equipment often adds features like digital charge of vacuum, digital display of temperature and rotational speed, and vapor temperature sensing.
Theory
Vacuum evaporators as a class function because decreasing the pressure above a bulk liquid lowers the boiling points in the component liquids in it. Generally, the component liquids of great interest in applications of rotary evaporation are research solvents that one desires to eliminate from the sample after an extraction, including following a natural product isolation or even a part of an organic synthesis. Liquid solvents can be taken off without excessive heating of the things are frequently complex and sensitive solvent-solute combinations.
Rotary evaporation is most often and conveniently applied to separate “low boiling” solvents this kind of n-hexane or ethyl acetate from compounds which can be solid at room temperature and pressure. However, careful application also allows removing of a solvent from a sample containing a liquid compound if you have minimal co-evaporation (azeotropic behavior), as well as a sufficient difference in boiling points in the chosen temperature and reduced pressure.
Solvents with higher boiling points such as water (100 °C at standard atmospheric pressure, 760 torr or 1 bar), dimethylformamide (DMF, 153 °C on the same), or dimethyl sulfoxide (DMSO, 189 °C on the same), can also be evaporated if the unit’s vacuum system is capable of doing sufficiently low pressure. (For instance, both DMF and DMSO will boil below 50 °C when the vacuum is reduced from 760 torr to 5 torr [from 1 bar to 6.6 mbar]) However, more modern developments tend to be applied in these instances (e.g., evaporation while centrifuging or vortexing at high speeds). Rotary evaporation for top boiling hydrogen bond-forming solvents including water can be a last recourse, as other evaporation methods or freeze-drying (lyophilization) can be purchased. This can be partly due to the fact that such solvents, the tendency to “bump” is accentuated. The modern centrifugal evaporation technologies are particularly useful when one has numerous samples to perform in parallel, like medium- to high-throughput synthesis now expanding in industry and academia.
Evaporation under vacuum could also, in principle, be practiced using standard organic distillation glassware – i.e., without rotation from the sample. The real key advantages being used of any rotary evaporator are
that the centrifugal force as well as the frictional force between the wall from the rotating flask and the liquid sample result in the formation of the thin film of warm solvent being spread over a large surface.
the forces developed by the rotation suppress bumping. A combination of those characteristics and the conveniences included in modern rotary evaporators enable quick, gentle evaporation of solvents from most samples, even at the disposal of relatively inexperienced users. Solvent remaining after rotary evaporation can be removed by exposing the sample to even deeper vacuum, on how to use rotary evaporator, at ambient or higher temperature (e.g., on the Schlenk line or in a vacuum oven).
A vital disadvantage in rotary evaporations, besides its single sample nature, is the chance of some sample types to bump, e.g. ethanol and water, which can lead to loss in a area of the material intended to be retained. Even professionals experience periodic mishaps during evaporation, especially bumping, though experienced users become aware of the propensity of some mixtures to bump or foam, and apply precautions which help to avoid most such events. Specifically, bumping can often be prevented through taking homogeneous phases in to the evaporation, by carefully regulating the potency of the vacuum (or perhaps the bath temperature) to supply for an even rate of evaporation, or, in rare cases, through use of added agents including boiling chips (to make the nucleation step of evaporation more uniform). Rotary evaporators can be equipped with further special traps and condenser arrays which can be suitable to particular difficult sample types, including those that have the tendency to foam or bump.
Safety
You can find hazards associated even with simple operations such as evaporation. Included in this are implosions resulting from utilization of glassware that contains flaws, such as star-cracks. Explosions may occur from concentrating unstable impurities during evaporation, for example when rotavapping an ethereal solution containing peroxides. This could also occur when taking tlpgsj unstable compounds, including organic azides and acetylides, nitro-containing compounds, molecules with strain energy, etc. to dryness.
Users of rotary evaporation equipment must take precautions to prevent connection with rotating parts, particularly entanglement of loose clothing, hair, or necklaces. Under these circumstances, the winding action from the rotating parts can draw users into the apparatus causing breakage of glassware, burns, and chemical exposure. Extra caution should also be applied to operations with air reactive materials, specially when under vacuum. A leak can draw air in to the apparatus and a violent reaction can happen.