A rotary evaporator (or rotavap/rotovap) is a device used in chemical laboratories for the effective and gentle removing of solvents from samples by evaporation. When referenced in the chemistry research literature, description of using this technique and equipment might 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 used 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 through 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 will be the 1L bench-top unit, whereas large scale (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 that is the axis for sample rotation, and it is a vacuum-tight conduit for your vapor being drawn off the sample.
A vacuum system, to substantially decrease 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 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 through the heating bath.
The rotovap parts used in combination 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 being a regulated mechanical vacuum pump with refrigerated trap. Glassware found in the vapor stream and condenser could be simple or complex, based upon the goals in the evaporation, as well as any propensities the dissolved compounds might share with the mixture (e.g., to foam or “bump”). Commercial instruments can be purchased that include the essential features, and other traps are produced to insert in between the evaporation flask as well as the vapor duct. Modern equipment often adds features such as digital control of vacuum, digital display of temperature and rotational speed, and vapor temperature sensing.
Vacuum evaporators as being a class function because reducing the pressure above a bulk liquid lowers the boiling points from the component liquids within it. Generally, the component liquids of great interest in applications of rotary evaporation are research solvents that a person desires to eliminate coming from a sample after an extraction, like using a natural product isolation or perhaps a element of an organic synthesis. Liquid solvents can be removed without excessive heating of the items are frequently 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), as well as 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 at the same), or dimethyl sulfoxide (DMSO, 189 °C in the same), can also be evaporated when the unit’s vacuum system is capable of doing 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 instances (e.g., evaporation while centrifuging or vortexing at high speeds). Rotary evaporation for high 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 in these solvents, the tendency to “bump” is accentuated. The present day centrifugal evaporation technologies are particularly useful when one has several samples to perform in parallel, as with medium- to high-throughput synthesis now expanding in industry and academia.
Evaporation under vacuum may also, in principle, be performed using standard organic distillation glassware – i.e., without rotation of the sample. The real key advantages used of any rotary evaporator are
that this 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 spanning a large surface.
the forces developed by the rotation suppress bumping. The combination of such 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 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).
A vital 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 loss 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 in order to avoid most such events. In particular, bumping can be prevented through taking homogeneous phases to the evaporation, by carefully regulating the potency of the vacuum (or perhaps the bath temperature) to offer to have an even rate of evaporation, or, in rare cases, through use of added agents like boiling chips (to create the nucleation step of evaporation more uniform). Rotary evaporators may also be designed with further special traps and condenser arrays that are most suitable to particular difficult sample types, including those that have the tendency to foam or bump.
You can find hazards associated even with simple operations like evaporation. Included in this are implosions resulting from utilization of glassware that contains flaws, like 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, including organic azides and acetylides, nitro-containing compounds, molecules with strain energy, etc. to dryness.
Users of rotary evaporation equipment have to take precautions to prevent 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 in to the apparatus leading to breakage of glassware, burns, and chemical exposure. Extra caution also must be applied to operations with air reactive materials, especially when under vacuum. A leak can draw air into the apparatus along with a violent reaction can happen.