A rotary evaporator (or rotavap/rotovap) is actually a device used in chemical laboratories for the efficient and gentle elimination of solvents from samples by evaporation. When referenced in the chemistry research literature, description of using 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 will also be found in molecular cooking for your preparation of distillates and extracts. A rotovap for sale was introduced by Lyman C. Craig. It was first 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 typical form is definitely the 1L bench-top unit, whereas massive (e.g., 20L-50L) versions are utilized 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 a vacuum-tight conduit for that vapor being drawn off of the sample.
A vacuum system, to substantially lessen the pressure inside 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 like dry ice and acetone are positioned.
A condensate-collecting flask at the bottom from the condenser, to catch 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 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 found in the vapor stream and condenser may be simple or complex, based on the goals from the evaporation, as well as any propensities the dissolved compounds might give to the mix (e.g., to foam or “bump”). Commercial instruments can be found including the fundamental features, and various traps are made to insert between the evaporation flask and 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 from the component liquids within it. Generally, the component liquids of interest in applications of rotary evaporation are research solvents that certain desires to eliminate from the sample after an extraction, like following a natural product isolation or even a part of an organic synthesis. Liquid solvents are easy to remove without excessive heating of what are often complex and sensitive solvent-solute combinations.
Rotary evaporation is frequently and conveniently applied to separate “low boiling” solvents this type of n-hexane or ethyl acetate from compounds which can be solid at room temperature and pressure. However, careful application also allows elimination of a solvent from the sample containing a liquid compound if you have minimal co-evaporation (azeotropic behavior), and 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 on the same), or dimethyl sulfoxide (DMSO, 189 °C at the same), can be evaporated in the event the unit’s vacuum system is capable of sufficiently low pressure. (For example, 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 are often applied in such cases (e.g., evaporation while centrifuging or vortexing at high speeds). Rotary evaporation for high boiling hydrogen bond-forming solvents such as water is usually a last recourse, as other evaporation methods or freeze-drying (lyophilization) can be found. This can be partly because of the fact that in these solvents, the tendency to “bump” is accentuated. The modern 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 could also, in principle, be practiced using standard organic distillation glassware – i.e., without rotation in the sample. The real key advantages in use of the rotary evaporator are
the centrifugal force as well as the frictional force involving the wall of the rotating flask as well as the liquid sample resulted in formation of a thin film of warm solvent being spread over a large surface.
the forces produced by the rotation suppress bumping. The mixture of those characteristics and also the conveniences that are part of modern rotary evaporators allow for quick, gentle evaporation of solvents from most samples, even at the disposal 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 rotary evaporator, at ambient or higher temperature (e.g., over a Schlenk line or in a vacuum oven).
A key disadvantage in rotary evaporations, besides its single sample nature, is the potential for some sample types to bump, e.g. ethanol and water, which can result in loss in a part of the material intended to be retained. Even professionals experience periodic mishaps during evaporation, especially bumping, though experienced users discover the propensity of some mixtures to bump or foam, and apply precautions that assist to avoid most such events. In particular, bumping can be prevented by taking homogeneous phases in to the evaporation, by carefully regulating the strength of the vacuum (or even the bath temperature) to supply 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 also be equipped with further special traps and condenser arrays which are most suitable to particular difficult sample types, including those that have the tendency to foam or bump.
There are hazards associated even with simple operations such as evaporation. Such as implosions resulting from utilization of glassware which has flaws, like 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, such as organic azides and acetylides, nitro-containing compounds, molecules with strain energy, etc. to dryness.
Users of rotary evaporation equipment need to take precautions in order to avoid contact with rotating parts, particularly entanglement of loose clothing, hair, or necklaces. In these situations, the winding action of the rotating parts can draw users into the apparatus leading to breakage of glassware, burns, and chemical exposure. Extra caution also must be used to operations with air reactive materials, especially when under vacuum. A leak can draw air in to the apparatus along with a violent reaction can happen.