A rotary evaporator (or rotavap/rotovap) is actually a device found in chemical laboratories for the effective and gentle elimination of solvents from samples by evaporation. When referenced in the chemistry research literature, description of using this technique and equipment may 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 are also used in molecular cooking for the preparation of distillates and extracts. A rotovap for sale was introduced 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 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 also a vacuum-tight conduit for that vapor being drawn off the sample.
A vacuum system, to substantially decrease the pressure in 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 like dry ice and acetone are put.
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 being a regulated mechanical vacuum pump with refrigerated trap. Glassware utilized in the vapor stream and condenser may be simple or complex, based on the goals in the evaporation, and any propensities the dissolved compounds might give the mixture (e.g., to foam or “bump”). Commercial instruments are available which include the essential features, and other traps are manufactured to insert involving the evaporation flask as well as the vapor duct. Modern equipment often adds features including digital control over vacuum, digital display of temperature and rotational speed, and vapor temperature sensing.
Vacuum evaporators as being a class function because lowering the pressure above a bulk liquid lowers the boiling points of the component liquids inside it. Generally, the component liquids appealing in uses of rotary evaporation are research solvents that one desires to get rid of from the sample after an extraction, including using a natural product isolation or a step in an organic synthesis. Liquid solvents can be taken off without excessive heating of the things are frequently 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 a sample containing a liquid compound when there is minimal co-evaporation (azeotropic behavior), along with a sufficient difference in boiling points on the chosen temperature and reduced pressure.
Solvents with higher boiling points like 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 also 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 when the vacuum is reduced from 760 torr to 5 torr [from 1 bar to 6.6 mbar]) However, more recent developments tend to be applied in these cases (e.g., evaporation while centrifuging or vortexing at high speeds). Rotary evaporation for top boiling hydrogen bond-forming solvents like water is usually a last recourse, as other evaporation methods or freeze-drying (lyophilization) are available. This 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, like medium- to high-throughput synthesis now expanding in industry and academia.
Evaporation under vacuum may also, in principle, be done using standard organic distillation glassware – i.e., without rotation from the sample. The true secret advantages in use of any rotary evaporator are
that the centrifugal force as well as the frictional force in between the wall in the rotating flask and the liquid sample result in the formation of any thin film of warm solvent being spread spanning a large surface.
the forces produced by the rotation suppress bumping. A combination of such characteristics and also 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 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., on the 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 may result in loss in a part 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 which help to avoid most such events. Particularly, bumping can be prevented if you take homogeneous phases in to the evaporation, by carefully regulating the potency of the vacuum (or perhaps the bath temperature) to provide to have an 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 be built with further special traps and condenser arrays which are most suitable to particular difficult sample types, including individuals with the tendency to foam or bump.
You will find hazards associated despite simple operations like evaporation. These include implosions caused by utilization 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 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 connection with rotating parts, particularly entanglement of loose clothing, hair, or necklaces. In these situations, the winding action of 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 to the apparatus as well as a violent reaction can occur.