The distillation efficiency of rotary evaporator determines the number of samples that can be distilled every day. What factors affect the distillation efficiency of rotary evaporator?
1. Vacuum value of the system
The confined space of rotary evaporator is composed of glass components such as evaporation bottle, evaporation tube, sealing ring, condensing tube, vacuum buffer bottle, vacuum pump and vacuum pipeline. Among them, the key and changeable factors affecting the vacuum of the system are vacuum pump, sealing ring and vacuum tube.
Vacuum pump and vacuum controller: the lower the vacuum pump, the lower the vacuum value of the system. In the process of distillation, it is necessary to set a reasonable vacuum value through the vacuum controller to ensure the distillation efficiency and avoid boiling. At present, the vacuum of diaphragm vacuum pump is as low as 2mbar, and that of circulating water pump is about 50mbar （0.095kpa）。 If the budget allows, a vacuum controller or valve is necessary to control the system vacuum value required for distillation.
Sealing ring: as the key sealing parts of evaporation pipe and condensation pipe, its wear resistance and corrosion resistance are the key. Commonly used as sealing ring material is: PTFE and rubber, obviously PTFE wear resistance and corrosion resistance will be good. Some manufacturers in the seal ring, added a stainless steel buffer spring, wear resistance is good.
Vacuum tube material: generally, manufacturers do not have standard vacuum tube. When purchasing by themselves, silicone tube is the choice, because its aging efficiency is slower than rubber tube.
2. Heating pot temperature
The higher the temperature of the heating pot, the faster the distillation effect of the solvent. However, considering the thermal sensitivity of the target component and the safety of the operation, the commonly used temperature is 60 ℃。 In addition, when the temperature is above 80 ° C, the use of silicone oil as the medium will bring about cleaning problems. It is generally recommended to reduce the vacuum value to achieve faster distillation efficiency. At present, the market, diaphragm vacuum pump, vacuum can reach 2mbar, DMF at room temperature can be distilled out.
3. Speed of evaporation bottle
At the same time, the thicker the liquid film thickness, the greater the heat transfer temperature difference. For materials with different viscosity, there is rotational speed. Moreover, the driving force is provided by the motor. There are DC brushless motor, AC motor and stepping motor on the market, which are uneven. The feedback of DC brushless motor is good, and maintenance is free for 10 years.