Rotary Evaporators Buying Guide

Rotary evaporators (rotovap) are mainly used to evaporate light boiling components under normal pressure or vacuum. When used in pilot plants and small-scale production they are also suitable for semi-continuous evaporation. They are characterized by providing a gentle thermal treatment for temperature-sensitive mediums and provide a higher evaporation rate as non-stirred glass distillation flasks. Compared to other evaporation processes the unique process feature of rotary evaporators is their ability to evaporate all volatile media providing at the end a dry product in the flask.

How to Use a Rotary Evaporator

* The concept of the rotovap entails motorized rotation of a solvent under reduced pressure.

* Lowering the pressure using a vacuum pump effectively reduces the boiling point of the solvent.

* Combined with heating, the newly evaporated solvent travels to a condenser vessel or coil where vapor is then converted into liquid form and separated into a collection flask.

By precisely varying pressure and temperature, a rotary evaporator can separate chemical constituents from a solvent mixture based primarily on the differences in boiling (and condensation) points of the components.

Rotary Evaporator Parts :

There are several main parts of a rotovap:

* Motorized unit rotates the starting solvent flask, which is partially submerged in a temperature-controlled water bath.

* Vacuum system and vapor duct allows the direct routing of evaporated solvent to the condenser.

* Condenser provides decreased temperature required to convert the vapor into liquid.

*  Condensate collection flask catches the condensed liquid.

A motorized unit allows quick lifting of the evaporation flask from the water bath to prevent sample loss.

Evaporator and Condenser

The evaporator and condenser work in close harmony.

* Solvent evaporation must occur with precision to selectively isolate the desired solvent, preventing co-evaporation or contamination with constituents of similar boiling points.

* The condenser must allow effective condensation relative to the objective of the separation, e.g. batch extraction versus stepwise distillation.

Evaporator Coil

The evaporation coil is typically a glass tube encased in a glass housing.

* This is either attached to a water aspirator, submerged in a cold bath, or placed in a refrigerated bath.

* The required precision of temperature control will depend on the complexity of the isolation method.

Vacuum Pump for Rotary Evaporation

Of critical importance in rotary evaporation processes is the maintenance of precise pressure in the system.

* Variations due to improper seals or inadequate vacuum pump performance can incur wide fluctuations in isolated compound yield and purity.

* Modern vacuum systems allow programmable methods, digital control, and sensors to ensure reliability and performance.

Solvent Evaporation - Rotary Evaporation Solvent Chart

Rotovap performance is best when the desired solvent isolates have low and distinctly different boiling points.

* Such solvents enable separation without extreme low vacuum pressures or excessively high heating temperatures.

* Thus, ultra-low vacuum consistency becomes less of a concern as does isolation of heat-sensitive compounds.

* A solvent evaporation chart assists in determining the best methods and evaporation conditions for a given project.

Rotovap Distillation

The more general term of distillation refers to isolation of distinct solvents from more complex mixtures.

* The rotovap builds off the distillation concept, with fine control of temperature, pressure, and timing to provide precise fractionation.

* Beyond these, there are additional elements that help drive the speed and accuracy of the rotovap process – and the throughput as well.

Thin Film Evaporation - Falling Film Evaporation - Wiped Film Evaporation

The rotating flask of the rotovap, through centrifugal and frictional forces, creates a thin film of solvent spread over a relatively large surface area of the flask. In combination with heat and vacuum, this solvent spreading leads to quick, gentle evaporation – avoiding the propensity for solvents to “bump”, or suddenly boil and expand from the reaction vessel.

Rotovaps are typically used in batch separation processes.

* On the other hand, continuous evaporation processes can make use of thin or wiped film evaporators.

* These systems use motorized “wipers” to continuously spread solvent on the surface of a heat-modulated vessel.

* The vapor travels upward through a condenser tube where the distillate is subsequently isolated and collected.

* Advantages of these systems include reduced time of exposure of the solvent to elevated temperatures as well as the ability to operate under continuous flow conditions.

These come at the cost of requirements for complex and often more expensive systems – the utility of which may or may not be needed for a given application.

Setting the Right Rotational Speed for your Rotary Evaporator

When operating a rotary evaporators in your lab, you want to make sure that you’re being as efficient as possible. One of the main factors to be considered is the rotational speed of your rotary evaporator, and while it might seem like maxing it out is your best option, it might not always be the case. You wouldn’t want things to spin out of control now, would you?

Some of the factors that you need to keep in mind when operating your rotary evaporator at its upper rotational speed is mechanical damage to your equipment caused by high speeds, and the decrease in evaporation rates beyond said speeds. 

Rotary Evaporation Manufacturer:

Across International is known as a popular manufacturer of rotary evaporation systems, having been in the business for many years and through many product advancements. Across International currently offers a range of systems to suit a range of applications, from entry level to R&D lab and quality control. Advanced features such as wireless touchscreen control, integrated vacuum pumps, and energy-saving recirculating chillers add to the capabilities and versatility of these devices.

Looking to buy?

If you are looking to purchase a new rotovap evaporator for your lab, we have a wide range of scientific instruments available. Call us for more details and get correct product for your Lab needs.