A rotary evaporator (or rotavap/rotovap) is actually a device found in chemical laboratories for the effective and gentle removal of solvents from samples by evaporation. When referenced in the chemistry research literature, description of the use of this method and equipment might 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 are also used in molecular cooking for your preparation of distillates and extracts. A rotary evaporators for sale was invented 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 definitely the 1L bench-top unit, whereas massive (e.g., 20L-50L) versions are used 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 which is the axis for sample rotation, and is also a vacuum-tight conduit for the vapor being drawn off the sample.
A vacuum system, to substantially reduce 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 perhaps a “cold finger” into which coolant mixtures such as dry ice and acetone are positioned.
A condensate-collecting flask in the bottom in the condenser, to trap 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 in combination with rotary evaporators may be as simple as being a water aspirator using 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 from the evaporation, and then any propensities the dissolved compounds might give the mix (e.g., to foam or “bump”). Commercial instruments are available that include the fundamental features, as well as other traps are made to insert in between the evaporation flask and the vapor duct. Modern equipment often adds features such as digital charge of vacuum, digital display of temperature and rotational speed, and vapor temperature sensing.
Vacuum evaporators being a class function because lowering the pressure above a bulk liquid lowers the boiling points in the component liquids within it. Generally, the component liquids of great interest in uses of rotary evaporation are research solvents that certain desires to remove coming from a sample after an extraction, like following a natural product isolation or perhaps a step in an organic synthesis. Liquid solvents can be removed without excessive heating of the things tend to be complex and sensitive solvent-solute combinations.
Rotary evaporation is frequently 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 coming from a sample containing a liquid compound if there is minimal co-evaporation (azeotropic behavior), as well as a sufficient difference in boiling points at the chosen temperature and reduced pressure.
Solvents with higher boiling points including water (100 °C at standard atmospheric pressure, 760 torr or 1 bar), dimethylformamide (DMF, 153 °C in the same), or dimethyl sulfoxide (DMSO, 189 °C at the same), can also be evaporated in the event the unit’s vacuum system can do sufficiently low pressure. (As an example, both DMF and DMSO will boil below 50 °C in the event 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 such cases (e.g., evaporation while centrifuging or vortexing at high speeds). Rotary evaporation for top boiling hydrogen bond-forming solvents such as water can be a last recourse, as other evaporation methods or freeze-drying (lyophilization) can be found. This can be partly simply because that such solvents, the tendency to “bump” is accentuated. The present day centrifugal evaporation technologies are particularly useful when one has several samples to perform in parallel, as in 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 of the sample. The true secret advantages being used of any rotary evaporator are
that this centrifugal force as well as the frictional force between the wall in the rotating flask and the liquid sample result in the formation of a thin film of warm solvent being spread more than a large surface.
the forces created by the rotation suppress bumping. A combination of such characteristics and the conveniences built into 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 taken off by exposing the sample to even deeper vacuum, on how to use rotary evaporator, at ambient or higher temperature (e.g., on a Schlenk line or in a vacuum oven).
A key disadvantage in rotary evaporations, besides its single sample nature, is the potential of some sample types to bump, e.g. ethanol and water, which may result in loss of a portion of the material supposed to have been retained. Even professionals experience periodic mishaps during evaporation, especially bumping, though experienced users start seeing the propensity of some mixtures to bump or foam, and apply precautions which help to avoid most such events. Particularly, bumping can be prevented through taking homogeneous phases into the evaporation, by carefully regulating the effectiveness of the vacuum (or even the bath temperature) to offer for the 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 also be designed with further special traps and condenser arrays which are best suited to particular difficult sample types, including individuals with the tendency to foam or bump.
You will find hazards associated even with simple operations including evaporation. Included in this are implosions caused by use of glassware which contains flaws, such as star-cracks. Explosions may occur from concentrating unstable impurities during evaporation, as an example when rotavapping an ethereal solution containing peroxides. This could also occur when taking tlpgsj unstable compounds, like organic azides and acetylides, nitro-containing compounds, molecules with strain energy, etc. to dryness.
Users of rotary evaporation equipment need to take precautions to avoid exposure to rotating parts, particularly entanglement of loose clothing, hair, or necklaces. In these situations, the winding action in the rotating parts can draw you in to the apparatus causing breakage of glassware, burns, and chemical exposure. Extra caution must also be applied to operations with air reactive materials, particularly when under vacuum. A leak can draw air into the apparatus along with a violent reaction can happen.