A rotary evaporator (or rotavap/rotovap) is a device found in chemical laboratories for the effective and gentle removing of solvents from samples by evaporation. When referenced in the chemistry research literature, description of the usage of this method and equipment can include the phrase “rotary evaporator”, though use is frequently 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 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 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 this is the axis for sample rotation, and it is a vacuum-tight conduit for the vapor being drawn off 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 a “cold finger” into which coolant mixtures such as dry ice and acetone are put.
A condensate-collecting flask in the bottom from the condenser, to trap the distilling solvent after it re-condenses.
A mechanical or motorized mechanism to quickly lift the evaporation flask from your heating bath.
The rotovap parts combined with rotary evaporators may 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 found in the vapor stream and condenser may be simple or complex, depending upon the goals of the evaporation, as well as any propensities the dissolved compounds might give the mixture (e.g., to foam or “bump”). Commercial instruments can be purchased including the basic features, and various 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 as being 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 a sample after an extraction, including after a natural product isolation or even a step in 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 such a n-hexane or ethyl acetate from compounds which are solid at room temperature and pressure. However, careful application also allows removing of a solvent from a sample containing a liquid compound if there is 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 in the same), or dimethyl sulfoxide (DMSO, 189 °C in the same), can 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 frequently applied in these 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 purchased. This can be partly because of the fact that 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, like medium- to high-throughput synthesis now expanding in industry and academia.
Evaporation under vacuum can also, in principle, be practiced using standard organic distillation glassware – i.e., without rotation of the sample. The true secret advantages used of the rotary evaporator are
the centrifugal force as well as the frictional force in between the wall from the rotating flask and also the liquid sample result in the formation of the thin film of warm solvent being spread over a large surface.
the forces produced by the rotation suppress bumping. The combination of such characteristics as well as the conveniences built into modern rotary evaporators allow for quick, gentle evaporation of solvents from most samples, even in the hands 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 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 of a area 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 in order to avoid most such events. In particular, bumping can be prevented if you take homogeneous phases to the evaporation, by carefully regulating the strength of the vacuum (or perhaps the bath temperature) to provide for the even rate of evaporation, or, in rare cases, through usage of added agents such as boiling chips (to make the nucleation step of evaporation more uniform). Rotary evaporators can be built with further special traps and condenser arrays that 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 like evaporation. These include implosions caused by usage of glassware which contains flaws, including 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 in order to avoid contact with rotating parts, particularly entanglement of loose clothing, hair, or necklaces. In these situations, the winding action in the rotating parts can draw the users to the apparatus leading to 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 into the apparatus along with a violent reaction can happen.