A rotary evaporator (or rotavap/rotovap) is a device utilized in chemical laboratories for the efficient and gentle removing of solvents from samples by evaporation. When referenced in the chemistry research literature, description of using this method and equipment may include the phrase “rotary evaporator”, though use is usually rather signaled by other language (e.g., “the sample was evaporated under reduced pressure”).
Rotary evaporators are also utilized in molecular cooking for that preparation of distillates and extracts. A rotovap for sale was designed 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 common form is the 1L bench-top unit, whereas large (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 that is the axis for sample rotation, and it is a vacuum-tight conduit for that vapor being drawn from the sample.
A vacuum system, to substantially lessen the pressure in the evaporator system.
A heated fluid bath (generally water) to heat the sample.
A condenser with either a coil passing coolant, or even a “cold finger” into which coolant mixtures such as dry ice and acetone are placed.
A condensate-collecting flask in the bottom of the condenser, to capture the distilling solvent after it re-condenses.
A mechanical or motorized mechanism to quickly lift the evaporation flask from the heating bath.
The rotovap parts used in combination with rotary evaporators may be as simple as a water aspirator having a trap immersed in a cold bath (for non-toxic solvents), or as complex being a regulated mechanical vacuum pump with refrigerated trap. Glassware found in the vapor stream and condenser may be simple or complex, depending upon the goals of the evaporation, and any propensities the dissolved compounds might give to the mix (e.g., to foam or “bump”). Commercial instruments can be found which include the basic features, and other traps are made to insert between the evaporation flask and also the vapor duct. Modern equipment often adds features including digital control of vacuum, digital display of temperature and rotational speed, and vapor temperature sensing.
Vacuum evaporators being a class function because reducing the pressure above a bulk liquid lowers the boiling points in the component liquids in it. Generally, the component liquids appealing in applications of rotary evaporation are research solvents that one desires to eliminate from the sample after an extraction, such as using a natural product isolation or a part of 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 most often and conveniently applied to separate “low boiling” solvents this type of n-hexane or ethyl acetate from compounds which are solid at room temperature and pressure. However, careful application also allows removal of a solvent from the sample containing a liquid compound when there is minimal co-evaporation (azeotropic behavior), along with a sufficient difference in boiling points in the chosen temperature and reduced pressure.
Solvents with higher boiling points like water (100 °C at standard atmospheric pressure, 760 torr or 1 bar), dimethylformamide (DMF, 153 °C at the same), or dimethyl sulfoxide (DMSO, 189 °C on the same), can also be evaporated if 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 are often applied in such cases (e.g., evaporation while centrifuging or vortexing at high speeds). Rotary evaporation for top boiling hydrogen bond-forming solvents like water is usually a last recourse, as other evaporation methods or freeze-drying (lyophilization) can be found. This really is partly due to the fact that in these solvents, the tendency to “bump” is accentuated. The modern centrifugal evaporation technologies are particularly useful when one has numerous samples to accomplish in parallel, as with medium- to high-throughput synthesis now expanding in industry and academia.
Evaporation under vacuum may also, in principle, be done using standard organic distillation glassware – i.e., without rotation of the sample. The real key advantages used of the rotary evaporator are
the centrifugal force and the frictional force between the wall of the rotating flask as well as the liquid sample resulted in formation of the thin film of warm solvent being spread spanning a large surface.
the forces produced by the rotation suppress bumping. The combination of these characteristics as well as the conveniences built into modern rotary evaporators enable quick, gentle evaporation of solvents from most samples, even in the hands 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 rotovap, at ambient or higher temperature (e.g., over a Schlenk line or in a vacuum oven).
An important disadvantage in rotary evaporations, besides its single sample nature, is the potential of some sample types to bump, e.g. ethanol and water, which can result in loss in a part 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 that assist to avoid most such events. Particularly, bumping can often be prevented through taking homogeneous phases into the evaporation, by carefully regulating the effectiveness of the vacuum (or even the bath temperature) to provide for the even rate of evaporation, or, in rare cases, through usage of added agents including boiling chips (to create the nucleation step of evaporation more uniform). Rotary evaporators can be equipped with further special traps and condenser arrays which are best suited to particular difficult sample types, including those with the tendency to foam or bump.
You can find hazards associated despite having simple operations including evaporation. These include implosions caused by utilization of glassware that 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 prevent connection with 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 resulting in breakage of glassware, burns, and chemical exposure. Extra caution must also be employed to operations with air reactive materials, particularly when under vacuum. A leak can draw air to the apparatus along with a violent reaction can occur.