Rotavap Lab

Rotavap Lab is mainly used for continuous distillation of a large number of volatile solvents under reduced pressure, especially for the concentration of extraction liquid and the distillation of receiving liquid during chromatographic separation, which can separate and purify reaction products. Its working principle is that the sample is placed in a circular container to increase the heating area through periodic rotation, so as to achieve the effect of evaporating water. Generally, it is more suitable to separate samples with more liquid or high and low melting points. The advantages are uniform heating and drying, but the disadvantages are that the instrument is easy to be damaged and the inner wall of glass is not easy to clean.

We provide Rotavap, please refer to the following website for detailed specifications and product information.

Product: https://www.achievechem.com/chemical-equipment/rotary-evaporators.html

The rotavap lab is suitable for separating samples with low melting point, because the rotovap makes the solution form a thin film in the evaporation bottle by heating and rotating, thus realizing an efficient evaporation process.

Generally speaking, samples with melting point below 100 degrees Celsius are more suitable for separation by rotavap. For example, some low-melting-point salts, esters, alcohols and other organic or inorganic substances have low melting points and will not undergo obvious decomposition or polymerization during heating.

However, for samples with high melting point, it may be difficult to use rotary evaporator machine for separation. Because with the increase of heating temperature, the sample may undergo decomposition or polymerization, resulting in poor separation effect. Therefore, for samples with high melting point, it may be necessary to adopt other methods for separation and purification, such as crystallization, recrystallization and extraction.

Extraction and purification of natural products

 

Natural products contain many impurities, which need to be separated and purified by rotary evaporator. For example, to extract natural products such as essential oils and pigments from plants, it is necessary to extract the components in the sample first, and then use a lab rotary evaporator to remove the extraction solvent, and finally get the target substance.

Detection and analysis of food additives

 

The analysis of food additives needs to extract and pretreat the sample, and then concentrate the extract for subsequent mass spectrometry analysis. At this time, the rotary evaporator can be used to concentrate the extract and remove the solvent to obtain the target sample.

The organic synthesis reaction in drug synthesis needs to prepare intermediates, and it is often necessary to remove the reaction solvent and purify the intermediates through a rotary evaporator. For example, volatile solvents such as chloroform need to be used in the preparation of some pharmaceutical synthesis intermediates, and then the reaction solvent can be removed by using a chemical rotary evaporator.

The principle of evaporation is the process of transforming liquid into gas, which needs to absorb heat from the surface of liquid. In the process of evaporation, liquid molecules constantly escape from the liquid surface to form vapor. This process will continue until the liquid is completely evaporated. Evaporation process can be used for material separation and purification, and solvent recovery. In the process of evaporation, there will be a phase change, that is, the liquid phase will change into the gas phase, which will be accompanied by the change of energy.

• Temperature: One of the most important conditions for evaporation. When the temperature of liquid rises, the kinetic energy of liquid molecules increases, and the interaction between molecules weakens. Molecules can overcome surface tension and atmospheric pressure and escape from the surface of liquid to form gas. Therefore, rising temperature will promote evaporation.
• Liquid surface area: The larger the liquid surface area, the more opportunities for evaporation. When the surface area of liquid increases, the contact area of liquid molecules with air also increases, and molecules can easily leave the liquid surface and enter the gas phase, thus increasing the evaporation rate.
• Wind speed: Wind speed will also affect the occurrence of evaporation. When the wind speed in the air increases, it will take away the water vapor on the liquid surface, making it easier for liquid molecules to leave the liquid surface and enter the gas phase. Therefore, the increase of wind speed will accelerate the evaporation.
• Heat source: Evaporation must consume heat. If there is no heat supply during evaporation, the evaporation surface will gradually cool down, thus reducing the water vapor pressure on the evaporation surface, so evaporation will slow down or stop gradually. Therefore, the evaporation rate depends largely on the supply of heat.
• Saturation deficit: Other factors being equal, the evaporation rate is directly proportional to saturation deficit. Strictly speaking, the saturated vapor pressure here should be calculated from the temperature of evaporation surface, but it is usually replaced by the saturated vapor pressure at a certain temperature.

As an important experimental equipment, the rotary evaporator's greatest social contribution is mainly reflected in promoting scientific research and technological innovation, environmental protection and sustainable development, and promoting the development of related fields. Through the application of evaporation system, we can better explore the laws of nature, develop new technologies and rotavap lab, and make positive contributions to social progress and development.

► Experimental procedure

1) Preparatory phase

Ensure that all components of the rotary evaporator are clean and in good working order.

Prepare the required distilling flask, receiving bottle and other glassware, and check its tightness.

2) Charging stage

The receiving liquid obtained by chromatographic separation is poured into the distillation flask, and the amount added is carefully controlled to avoid too much or too little.

Install the distillation flask correctly on the rotary evaporator and ensure that it is well sealed.

3) Set parameters

According to the solvent properties and experimental requirements of the receiving liquid, set the appropriate heating temperature, rotation speed and vacuum degree.

Make sure the cooling water of the condenser is turned on and adjusted to the appropriate temperature.

4) Start the experiment

Start the rotary evaporator and start the distillation flask to rotate.

At the same time, the heating device is turned on to heat the solvent in the distillation flask.

Under reduced pressure, the solvent begins to evaporate and is cooled into a liquid through the condenser, which flows into the receiving bottle.

5) Monitoring and adjustment

During the experiment, it is necessary to pay close attention to the liquid level changes in the distillation flask and the liquid collection in the receiving flask.

If the liquid level is abnormal or boiling phenomenon is found, the experiment should be stopped immediately and the cause should be checked.

According to the needs of the experiment, the heating temperature, rotation speed and vacuum degree can be adjusted in time.

6) End the experiment

When enough liquid has been collected in the receiving bottle, the experiment can be stopped.

Close the heating device and rotation function of the rotary evaporator, and open the valve in communication with the atmosphere, so that the pressure in the distillation flask is gradually restored to normal pressure.

The distillation flask and receiving flask are removed for subsequent purification and analysis.

► Problems and solutions

1) The rotation speed is not stable

Problem analysis:

 The motor is faulty.

 The transmission belt is loose.

The solution:

 Check whether the motor is working normally, if there is a fault, it needs to be repaired or replaced in time.

 Make sure the belt is tight and should be re-adjusted or replaced if loose.

 Low evaporation efficiency

Problem analysis:

 The temperature of the condenser is too high.

 Insufficient vacuum.

The solution:

 Adjust the condenser temperature to ensure that it is within the appropriate range.

 Check the vacuum system to ensure that the vacuum degree meets the experimental requirements. If there is air leakage, check and replace the sealing ring or re-apply vacuum grease.

2) The solution does not boil evenly

Problem analysis:

 There are solid particles in the solution.

 There are bubbles in the solution.

The solution:

 Filter the solution to remove solid particles.

 Gently tap the bottle or use an ultrasonic bath to remove air bubbles.

3) Bottle mouth seal is not good

Problem analysis:

 The mouth of the bottle is worn.

 The sealing ring is aging.

The solution:

 Replace worn bottle tops.

 Replace the aging seal ring.

4) Excessive noise

Problem analysis:

 Mechanical parts wear out.

 Mechanical parts are not balanced.

The solution:

 Check whether mechanical parts need to be replaced.

 Re-balance the mechanical components.

5) The vacuum can not be pumped up or the vacuum degree becomes smaller

Problem analysis:

 There is solvent in the container.

 Vacuum pump capacity decreased.

 The vacuum hose connector is loose.

 There are debris in the discharge valve and pressure control valve.

 The glass fiber wool sandwich panel is damaged.

The solution:

 Empty solvent, empty bottle test vacuum.

 Replace the oil or water of the vacuum pump, clean and repair the vacuum pump.

 Detect and remove air leakage points step by step along the vacuum line.

 Reassembly, glass wool sandwich board scrub clean apply vacuum silicone grease or replace failed seals.

 Clean and repair related parts.

6) The bath pan is not heated or heated abnormally

Problem analysis:

 The power supply is abnormal.

 Heating coil, solid state relay, or relay board failure.

 The temperature controller is faulty.

 The probe is improperly connected or damaged.

The solution:

 Check whether the power supply is normal. If any exception occurs, repair it in time.

 Replace damaged heating coils, solid-state relays or relay boards.

 Replace the faulty temperature controller.

 Check whether the probe is properly connected and replace the damaged probe.

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