A rotary evaporator (or rotavap/rotovap) is a device found in chemical laboratories for the efficient and gentle elimination of solvents from samples by evaporation. When referenced in the chemistry research literature, description of the usage of this technique 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 will also be used in molecular cooking for your preparation of distillates and extracts. A rotary evaporators for sale 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 common form will be 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 the vapor being drawn from the sample.
A vacuum system, to substantially reduce 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 such as dry ice and acetone are put.
A condensate-collecting flask in 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 used in combination with rotary evaporators can be as simple as a water aspirator with a trap immersed in a cold bath (for non-toxic solvents), or as complex being a regulated mechanical vacuum pump with refrigerated trap. Glassware used in the vapor stream and condenser may be simple or complex, based upon the goals of the evaporation, and then any propensities the dissolved compounds might give the mix (e.g., to foam or “bump”). Commercial instruments can be found that include the essential features, and other traps are made to insert in 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 as a class function because lowering the pressure above a bulk liquid lowers the boiling points in the component liquids inside it. Generally, the component liquids of interest in applications of rotary evaporation are research solvents that a person desires to get rid of from the sample after an extraction, such as following a natural product isolation or even a step in an organic synthesis. Liquid solvents can be removed without excessive heating of the items tend to be complex and sensitive solvent-solute combinations.
Rotary evaporation is frequently and conveniently put on 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 removing 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 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 on the same), or dimethyl sulfoxide (DMSO, 189 °C at the same), can also be evaporated when the unit’s vacuum system is capable of doing sufficiently low pressure. (For 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 like water is usually a last recourse, as other evaporation methods or freeze-drying (lyophilization) can be purchased. This really is partly simply because that such solvents, the tendency to “bump” is accentuated. The present day centrifugal evaporation technologies are particularly useful when one has many samples to do in parallel, as with medium- to high-throughput synthesis now expanding in industry and academia.
Evaporation under vacuum could also, in principle, be performed using standard organic distillation glassware – i.e., without rotation of the sample. The real key advantages used of the rotary evaporator are
the centrifugal force and also the frictional force in between the wall from the rotating flask and also the liquid sample result in the formation of any thin film of warm solvent being spread over a large surface.
the forces developed by the rotation suppress bumping. The combination of these characteristics and also the conveniences built into 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).
An important 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 result in 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 to avoid most such events. Specifically, bumping is often prevented through taking homogeneous phases to the evaporation, by carefully regulating the strength of the vacuum (or the bath temperature) to offer for the even rate of evaporation, or, in rare cases, through utilization of added agents such as boiling chips (to make the nucleation step of evaporation more uniform). Rotary evaporators may also be built with further special traps and condenser arrays which can be suitable to particular difficult sample types, including individuals with the tendency to foam or bump.
You will find hazards associated even with simple operations like evaporation. Included in this are implosions caused by utilization of glassware which contains flaws, such as 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, 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 in order to avoid exposure to rotating parts, particularly entanglement of loose clothing, hair, or necklaces. In these situations, the winding action from the rotating parts can draw you to the apparatus leading to breakage of glassware, burns, and chemical exposure. Extra caution should also be employed to operations with air reactive materials, specially when under vacuum. A leak can draw air in to the apparatus along with a violent reaction can occur.