A rotary evaporator (or rotavap/rotovap) is actually a device used in chemical laboratories for the effective and gentle elimination of solvents from samples by evaporation. When referenced in the chemistry research literature, description of the use of this method and equipment can include the phrase “rotary evaporator”, though use is often rather signaled by other language (e.g., “the sample was evaporated under reduced pressure”).
Rotary evaporators will also be used in molecular cooking for your preparation of distillates and extracts. A rotovap for sale was introduced 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 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 that is the axis for sample rotation, and is also a vacuum-tight conduit for that vapor being drawn off of 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 even a “cold finger” into which coolant mixtures including dry ice and acetone are positioned.
A condensate-collecting flask towards 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 as a water aspirator using a trap immersed in a cold bath (for non-toxic solvents), or as complex as being a regulated mechanical vacuum pump with refrigerated trap. Glassware found in the vapor stream and condenser could be simple or complex, depending upon the goals from the evaporation, as well as any propensities the dissolved compounds might share with the mix (e.g., to foam or “bump”). Commercial instruments can be purchased which include the basic features, as well as other traps are produced to insert involving the evaporation flask and the vapor duct. Modern equipment often adds features such as digital control over 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 inside it. Generally, the component liquids appealing in applications of rotary evaporation are research solvents that certain desires to remove from a sample after an extraction, like after a natural product isolation or a part of an organic synthesis. Liquid solvents can be taken off 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 kind of n-hexane or ethyl acetate from compounds that are solid at room temperature and pressure. However, careful application also allows elimination of a solvent coming from a sample containing a liquid compound if there is minimal co-evaporation (azeotropic behavior), and 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 in the same), or dimethyl sulfoxide (DMSO, 189 °C on the same), may also be evaporated in the event 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 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) are available. 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 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 done using standard organic distillation glassware – i.e., without rotation of the sample. The key advantages in use of a rotary evaporator are
the centrifugal force and the frictional force between the wall in the rotating flask and also the liquid sample resulted in formation of a thin film of warm solvent being spread spanning a large surface.
the forces created by the rotation suppress bumping. The combination of these characteristics and also the conveniences included in modern rotary evaporators enable 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 rotovap, at ambient or higher temperature (e.g., on a Schlenk line or in a vacuum oven).
A key 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 lead to loss in a portion of the material intended to be 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 which help in order to avoid most such events. In particular, bumping can be prevented by taking homogeneous phases into the evaporation, by carefully regulating the potency of the vacuum (or perhaps the bath temperature) to offer for an 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 designed with further special traps and condenser arrays that are suitable to particular difficult sample types, including those with the tendency to foam or bump.
You can find hazards associated even with simple operations including evaporation. Such as implosions caused by use of glassware which has flaws, including star-cracks. Explosions may occur from concentrating unstable impurities during evaporation, for instance when rotavapping an ethereal solution containing peroxides. This can 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 have to take precautions to avoid connection with rotating parts, particularly entanglement of loose clothing, hair, or necklaces. In these situations, the winding action from the rotating parts can draw you into the apparatus causing breakage of glassware, burns, and chemical exposure. Extra caution should also be applied 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.