What is a Rotary Evaporator?

A rotary evaporator is a device used in laboratories for the efficient and gentle removal of solvents from samples by evaporation. Scientists often talk about a sample being evaporated under reduced pressure - ie in a rotary evaporator.

Rotary evaporators are also used in molecular cooking for the preparation of distillates and extracts.

 

The main components of a rotary evaporator are:

1. A motor unit that rotates the evaporation flask or vial containing the user's sample.
2. A vapour duct that is the axis for sample rotation, and is a vacuum-tight conduit for the vapour being drawn off of the sample.
3. A vacuum system, to substantially reduce the pressure within the evaporator system.
4. A heated fluid bath (generally water) to heat the sample.
5. A condenser with either a coil passing coolant, or a "cold finger" into which coolant mixtures such as dry ice and acetone are placed.
6. A condensate-collecting flask at the bottom of the condenser, to catch the distilling solvent after it re-condenses.
7. A mechanical or motorised mechanism to quickly lift the evaporation flask from the heating bath.

The vacuum system used 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 as a regulated mechanical vacuum pump with refrigerated trap.

Glassware used in the vapour stream and condenser can be simple or complex, depending upon the goals of the evaporation, and any propensities the dissolved compounds might give to the mixture (e.g., to foam or "bump").

Commercial instruments are available that include the basic features, and various traps are manufactured to insert between the evaporation flask and the vapour duct. Modern equipment often adds features such as digital control of vacuum such as the KNF SC950 unit shown below, digital display of temperature and rotational speed, and vapour temperature sensing.

Users of rotary evaporators must take precautions to avoid contact with rotating parts, particularly entanglement of loose clothing, hair, or necklaces. Under these circumstances, the winding action of the rotating parts can draw the users into the apparatus resulting in breakage of glassware, burns, and chemical exposure. Extra caution must also be applied to operations with air reactive materials, especially when under vacuum. A leak can draw air into the apparatus and a violent reaction can occur.  Care must also be taken to avoid implosions resulting from use of glassware that contains flaws, such as star-cracks. Explosions may occur from concentrating unstable impurities during evaporation.

What would it be like... if you could just disappear from the daily lab routine? As easily and quickly as liquid escapes from the rotary evaporator? This is the fantasy in the IKA image video above.

For more information visit:-
http://en.wikipedia.org/wiki/Rotary_evaporator
https://www.prlabs.co.uk/news/article.php?Id=120
http://www.knf.co.uk/products/laboratory-pumps/product/categories/vacuum-pump-systems/
http://www.ika.com/Products-Lab-Eq/Rotary-Evaporators-Rotary-evaporator-distilling-distillation-cph-35/
http://www.heidolph-instruments.com/products/rotary-evaporators/
http://www.stuart-equipment.com/category.asp?dsl=118&mnu=23

All available through P&R Labpak Limited

Distilled or Deionised Water? What's the difference?

Many laboratory staff ask for purified water and use the terms distilled and deionised interchangeably.  However the actual products are different and are produced differently.

Most commonly now deionised water is supplied when people ask for purified water.

Purified water is water that is mechanically filtered or processed to be cleaned for consumption. Distilled water and deionised (DI) water have been the most common forms of purified water, but water can also be purified by other processes including Reverse osmosis, carbon filtration, microfiltration, ultrafiltration, ultraviolet oxidation, or electrodialysis.

Distilled water is produced by a process of distillation and has an electrical conductivity of not more than 11 µS/cm and total dissolved solids of less than 10 mg/litre.  Distillation involves boiling the water and then condensing the vapour into a clean container, leaving solid contaminants behind. Distillation produces very pure water. A white or yellowish mineral scale is left in the distillation apparatus, which requires regular cleaning. Distillation alone does not guarantee the absence of bacteria in drinking water unless containers are also sterilized. For many procedures more economical alternatives are available such as deionised water and, is used in place of distilled water.

Double distillation - Double-distilled water is prepared by double distillation of water. Historically, it was the de facto standard for highly purified laboratory water for biochemistry and, by the method of trace analysis until combination methods of purification became widespread.

A water still (Stuart Merit W4000)

Deionisation - Deionised water, also known as demineralised water, is water that has had its mineral ions removed, such as cations like sodium, calcium, iron, and copper, and anions such as chloride and sulfate. Deionisation is a chemical process that uses specially manufactured ion-exchange resins which exchange hydrogen ion and hydroxide ion for dissolved minerals, which then recombine to form water. Because the majority of water impurities are dissolved salts, deionisation produces a high purity water that is generally similar to distilled water, and this process is quick and without scale buildup. However, deionisation does not significantly remove uncharged organic molecules, viruses or bacteria, except by incidental trapping in the resin. Specially made strong base anion resins can remove Gram-negative bacteria. Deionisation can be done continuously and inexpensively using electrodeionisation.

Purite Labwater Deioniser

Outside of the laboratory deionised or distilled water is used to top us lead-acid car batteries although many units are now sealed.  Purified water is also used in freshwater and marine aquariums. As it doesn't contain impurities such as copper and chlorine, it helps to keep fish free from diseases and avoids the build-up of algae on aquarium plants due to its lack of phosphate and silicate.

Deionised water is available from P&R Labpak in small through to large containers!  We can also supply equipment if you need to make your own.

To read more on water:-
https://en.wikipedia.org/wiki/Deionised_water
http://www.prlabs.co.uk/lab-supplies.php?N=ANALYST-40-WITH-BOOST-PUMP&Id=40933
http://www.prlabs.co.uk/lab-supplies.php?N=STILL-MERIT-MODEL-W4000&Id=45943

 

 

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