A rotary evaporator (or rotavap/rotovap) is actually a device found in chemical laboratories for the efficient and gentle removal of solvents from samples by evaporation. When referenced in the chemistry research literature, description of the usage of this method and equipment might 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 can also be found in molecular cooking for that preparation of distillates and extracts. A rotary evaporator was designed by Lyman C. Craig. It was initially commercialized from 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 large (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 which is the axis for sample rotation, and is a vacuum-tight conduit for your vapor being drawn off of 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 a “cold finger” into which coolant mixtures such as dry ice and acetone are put.
A condensate-collecting flask at 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 combined with rotary evaporators could be as simple as 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 could be simple or complex, based on the goals in the evaporation, as well as any propensities the dissolved compounds might share with the mix (e.g., to foam or “bump”). Commercial instruments are available including the essential features, and other traps are manufactured to insert involving the evaporation flask and the vapor duct. Modern equipment often adds features like digital charge of vacuum, digital display of temperature and rotational speed, and vapor temperature sensing.
Vacuum evaporators as being a class function because decreasing the pressure above a bulk liquid lowers the boiling points of the component liquids within it. Generally, the component liquids of great interest in uses of rotary evaporation are research solvents that one desires to eliminate from a sample after an extraction, including following a natural product isolation or even a element of an organic synthesis. Liquid solvents are easy to remove without excessive heating of the things tend to be complex and sensitive solvent-solute combinations.
Rotary evaporation is most often and conveniently placed on separate “low boiling” solvents this type of n-hexane or ethyl acetate from compounds that are solid at room temperature and pressure. However, careful application also allows removing of a solvent from the sample containing a liquid compound if you have 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 such as 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 in the same), may also be evaporated when the unit’s vacuum system is capable of doing sufficiently low pressure. (For instance, 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 frequently applied in these cases (e.g., evaporation while centrifuging or vortexing at high speeds). Rotary evaporation for high boiling hydrogen bond-forming solvents such as water is often a last recourse, as other evaporation methods or freeze-drying (lyophilization) can be found. This can be partly because of the fact that in such solvents, the tendency to “bump” is accentuated. The present day centrifugal evaporation technologies are particularly useful when one has many samples to perform in parallel, as in medium- to high-throughput synthesis now expanding in industry and academia.
Evaporation under vacuum can also, in principle, be performed using standard organic distillation glassware – i.e., without rotation in the sample. The real key advantages in use of a rotary evaporator are
the centrifugal force and the frictional force between the wall from the rotating flask and the liquid sample resulted in formation of any thin film of warm solvent being spread more than a large surface.
the forces created by the rotation suppress bumping. The combination of such characteristics and also the conveniences that are part of modern rotary evaporators permit quick, gentle evaporation of solvents from most samples, even in the hands of relatively inexperienced users. Solvent remaining after rotary evaporation are easy to remove by exposing the sample to even deeper vacuum, on how to use rotovap, at ambient or higher temperature (e.g., on a 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 part of the material supposed to have been 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 that assist to avoid most such events. Particularly, bumping is often prevented through taking homogeneous phases to the evaporation, by carefully regulating the effectiveness of the vacuum (or the bath temperature) to provide for the even rate of evaporation, or, in rare cases, through utilization of added agents such as boiling chips (to create 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.
You will find hazards associated despite simple operations including evaporation. Included in this are implosions caused by utilization of glassware which has flaws, like star-cracks. Explosions may occur from concentrating unstable impurities during evaporation, for instance when rotavapping an ethereal solution containing peroxides. This could also occur when taking tlpgsj unstable compounds, such as organic azides and acetylides, nitro-containing compounds, molecules with strain energy, etc. to dryness.
Users of rotary evaporation equipment must take precautions in order to avoid contact 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 resulting in breakage of glassware, burns, and chemical exposure. Extra caution should also be used to operations with air reactive materials, especially when under vacuum. A leak can draw air into the apparatus and a violent reaction can happen.