Views: 6 Author: Site Editor Publish Time: 2021-12-02 Origin: Site
Practical skills to improve the distillation efficiency of rotary evaporators
The distillation efficiency of the rotary evaporator determines the number of samples that can be distilled every day. In the case of the same solvent, the higher the distillation efficiency, the more samples that can be distilled. So what are the practical skills to improve the distillation efficiency of the rotary evaporator?
1. The vacuum value of the system
The vacuum degree is the most important process parameter of the rotary evaporator, and users often encounter the problem that the vacuum degree cannot be reached. This is often related to the nature of the solvent used. In biochemical and pharmaceutical industries, water, ethanol, acetic acid, petroleum ether, chloroform, etc. are commonly used as solvents, while general vacuum pumps cannot withstand strong organic solvents. Special vacuum pumps with strong corrosion resistance can be selected. Water circulation is recommended. Vacuum pump.
From the structural point of view, the enclosed space of the rotary evaporator is composed of glass components such as evaporating flask, evaporating tube, sealing ring, condenser tube, vacuum buffer bottle, vacuum pump, and vacuum pipeline. Among them, the most critical and variable factors affecting the vacuum of the system Yes: vacuum pump, sealing ring and vacuum tube.
Vacuum pump and vacuum controller: The lower the vacuum pump limit, the lower the vacuum value of the system. When distilling, it is necessary to set a reasonable vacuum value through the vacuum controller to ensure the distillation efficiency while avoiding bumping. At present, the ultimate vacuum of the diaphragm vacuum pump can reach 2mbar, and the ultimate vacuum of the circulating water pump is about 50mbar (0.095kpa). If the budget permits, a vacuum controller or vacuum valve is necessary, which can control the system vacuum required for distillation.
Sealing ring: As a key seal for the evaporator tube and condenser tube, its wear resistance and corrosion resistance are the key. The materials commonly used as sealing rings are: PTFE and rubber. Obviously, the wear resistance and corrosion resistance of PTFE will be better. Individual manufacturers add stainless steel buffer shrapnel to the seal ring, which has better wear resistance.
Vacuum tube material: Generally, the manufacturers do not have standard vacuum tubes. When purchasing by themselves, silicone tubes are naturally the best, because their aging efficiency is slower than that of rubber tubes.
2. Heating pot temperature
The higher the heating pot temperature, the faster the solvent distillation effect, but considering the heat sensitivity of the target component and the safety of operation, the commonly used temperature is 60°C. In addition, above 80°C, changing to silicone oil as the medium will cause cleaning problems. Generally, it is recommended to lower the vacuum value to achieve faster distillation efficiency. Currently on the market, *diaphragm vacuum pumps can reach an ultimate vacuum of 2mbar, and DMF can be distilled at room temperature.
3. Rotation speed of evaporating flask
The faster the rotating speed of the evaporating flask, the larger the infiltration area of the inner surface of the flask and the larger the heated area; but at the same time, the thicker the liquid film thickness will increase the heat transfer temperature difference. For materials with different viscosities, there is an optimal speed. And the rotating power is provided by the motor. There are brushless DC motors, AC motors and stepping motors on the market, and they are uneven. The feedback of the DC brushless motors is very good.
4. The temperature of the cooling medium
In order to ensure the best distillation efficiency, the cooling medium is generally recommended to maintain a temperature difference of 40°C with the temperature of the heating pot in order to quickly condense the hot steam and reduce the influence of the steam on the vacuum of the system.