A rotary evaporator (or rotavap/rotovap) is a device used in chemical laboratories for the efficient 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 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 the 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 frequent form is the 1L bench-top unit, whereas massive (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 this is the axis for sample rotation, and it is a vacuum-tight conduit for your vapor being drawn from the sample.
A vacuum system, to substantially lessen 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 including dry ice and acetone are positioned.
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 through the heating bath.
The rotovap parts used in combination with rotary evaporators may be as simple being a water aspirator using a trap immersed in a cold bath (for non-toxic solvents), or as complex being a regulated mechanical vacuum pump with refrigerated trap. Glassware utilized in the vapor stream and condenser could be simple or complex, depending upon the goals of the evaporation, and any propensities the dissolved compounds might share with the mixture (e.g., to foam or “bump”). Commercial instruments can be found including the essential features, as well as other traps are produced to insert in between the evaporation flask as well as the vapor duct. Modern equipment often adds features like digital control of vacuum, digital display of temperature and rotational speed, and vapor temperature sensing.
Vacuum evaporators as a class function because lowering the pressure above a bulk liquid lowers the boiling points of the component liquids in it. Generally, the component liquids of interest in uses of rotary evaporation are research solvents that certain desires to eliminate coming from a sample after an extraction, including after a natural product isolation or even a part of an organic synthesis. Liquid solvents can be taken off without excessive heating of the items are frequently complex and sensitive solvent-solute combinations.
Rotary evaporation is frequently and conveniently placed on 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 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 on the same), may also be evaporated when the unit’s vacuum system is capable of 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 recent developments are often applied in these instances (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) are available. This is partly due to the fact that such solvents, the tendency to “bump” is accentuated. The current centrifugal evaporation technologies are particularly useful when one has several samples to accomplish in parallel, as with 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 from the sample. The real key advantages used of a rotary evaporator are
that the centrifugal force as well as the frictional force between the wall from the rotating flask and also the liquid sample result in the formation of a thin film of warm solvent being spread over a large surface.
the forces developed by the rotation suppress bumping. The combination of these characteristics as well as the conveniences built into modern rotary evaporators permit 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 the Schlenk line or in a vacuum oven).
An important disadvantage in rotary evaporations, besides its single sample nature, is the potential for some sample types to bump, e.g. ethanol and water, which may result in lack of a portion of the material intended to be 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 which help to avoid most such events. In particular, bumping can often be prevented through taking homogeneous phases into the evaporation, by carefully regulating the strength of the vacuum (or the bath temperature) to supply to have an even rate of evaporation, or, in rare cases, through utilization of added agents like boiling chips (to help make the nucleation step of evaporation more uniform). Rotary evaporators can also be designed with further special traps and condenser arrays that are best suited to particular difficult sample types, including those that have the tendency to foam or bump.
You can find hazards associated despite having simple operations including evaporation. Included in this are implosions caused by use of glassware which contains flaws, like star-cracks. Explosions may occur from concentrating unstable impurities during evaporation, as an example when rotavapping an ethereal solution containing peroxides. This can 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 must take precautions to prevent contact with rotating parts, particularly entanglement of loose clothing, hair, or necklaces. Under these circumstances, the winding action in the rotating parts can draw you in to the apparatus causing breakage of glassware, burns, and chemical exposure. Extra caution should 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 occur.