Mumuxili Instrument said, "Let's talk about rotary evaporation in detail.

Comments · 156 Views

Mumuxili Instrument said, "Let's talk about rotary evaporation in detail. Come and see!"! _ Condensation

Original Title: Mumuxili Instrument: Talk about Rotary Evaporation in Detail, Come and See! Rotary evaporator, also known as rotary evaporator, is mainly used in the pretreatment process of food, environment and other samples. Its main function is to concentrate and convert the solvent. It is mainly composed of a motor, a distillation flask, a heating pot, a condenser tube and other parts of the common laboratory equipment. Take a deep look at this little cutie with sister Xiaoxi. Basic structure and principle The working principle of rotary evaporation is simply to make the distillation flask rotate at a constant speed at the most appropriate speed through motor control to increase the evaporation area, and at the same time, to make the evaporation flask in a negative pressure state through vacuum pump pumping to reduce the boiling point of the solution and accelerate the evaporation rate. Vacuum evaporators are used as a means of evaporation, because lowering the pressure above the liquid will lower the boiling point of the component liquid, thus speeding up the evaporation rate to a certain extent. The evaporation bottle is arranged in the water bath kettle to be heated at constant temperature while rotating, and the solution in the bottle is heated, diffused and evaporated under the condition of negative pressure in the rotating bottle. The evaporation system can be sealed and decompressed to 400 to 600 millimeters of mercury, the solvent in the distillation flask is heated by a heating bath, the heating temperature can be close to the boiling point of the solvent, meanwhile, the solvent can be rotated at a speed of 50 to 160 revolutions per minute to form a film to increase the evaporation area, and in addition, the hot vapor can be quickly liquefied under the action of a high-efficiency condenser tube to accelerate the distillation rate. Typically in rotary evaporation applications, the constituent liquid of interest is the study solvent that one wishes to remove from the sample after extraction, for example after a step in natural product isolation or organic synthesis, where the liquid solvent can be removed without undue heating of the often complex and sensitive solvent mixture. Rotary evaporation is most commonly and conveniently used to separate "low-boiling" solvents such as n-hexane or ethyl acetate from compounds that are solid at room temperature and pressure. However, if there is minimal co-evaporation (azeotropic behavior), and sufficient difference in boiling points at the selected temperature and reduced pressure, careful application also allows the solvent to be removed from the sample containing the liquid compound. Main components of rotary evaporation 1. Rotate the motor to drive the evaporation bottle. 2. Evaporation pipe, the support shaft for the rotation of the evaporation bottle, and the vacuum-sealed pipe for extracting steam from the material. 3, vacuum system, reduce the pressure in the evaporator system, reduce the boiling point of materials. 4. Water or oil is often used to heat materials in the heating bath. 5. Condenser. In order to speed up the condensation efficiency, it is usually made into a double-snake encircling type, and then a condensing agent such as dry ice and acetone is added to condense the sample. Expand the full text 6. The condensate collection bottle at the bottom of the condenser is used to capture the distillation solvent after recondensation and collect the sample. 7. Lifting device, a mechanical or motorized mechanism that can quickly lift the evaporation bottle from the heating bath. The Development of Rotary Evaporator 1. Wool condenser Ancient Greek sailors noticed the condensation of mist droplets on the sails, and sailors put wool over a heated pot to obtain fresh water, which was later called wool condenser. 2. The study of Aristotle In 350 BC in ancient Greece, Aristotle studied the principles of distillation and condensation, and discovered the important law of water circulation in nature. "By distilling water into steam and then into liquid, sea water can be turned into drinkable water.". 3. The study of alchemists In the 2nd century AD, alchemists developed the earliest copper distillation device, the "distillation pot". 4. Appearance of vacuum distillation In the 17th century, Robert Boyle, an Irish physicist, carried out the first revolutionary vacuum distillation, which proved the relationship between pressure and boiling point, and the distillation speed was greatly improved. 5. Rotating distillation flask and commercial rotary evaporator In the 1950s, scientists C. C. Draig and M. E. Volk proposed the concept of rotating flask to achieve better mixing and larger area heating of samples. At the same time, the earliest commercial rotary evaporator was born. 6. The Age of Intelligent Rotary Steaming In the 21st century, the wave of artificial intelligence has swept the world. With the continuous advancement of laboratory automation, intelligent rotary steaming has become the standard of modern laboratories. Maintenance knowledge of rotary evaporator 1. Carefully check the instrument before use to see whether the glass bottle is damaged and whether the interfaces are matched. Handle with care. 2. Wipe each interface with a soft cloth (napkin can be used instead), and then apply a little vacuum grease. Vacuum grease must be covered after use to prevent dust and sand from entering. 3. Each interface shall not be tightened too tightly, and shall be loosened and loosened regularly, so as to avoid seizure of the connector caused by long-term locking. 4. Turn on the power switch first, and then let the machine run from slow to fast. When the machine is stopped, the machine should be in a stop state, and then turn off the switch. 5. The Teflon switches at all places shall not be tightened with excessive force, which is easy to damage the glass. 6. After each use, all kinds of oil stains, stains and solvent residues left on the surface of the machine must be wiped with a soft cloth to keep them clean. 7. Loosen each PTFE switch after shutdown. The PTFE piston will be deformed if it is still in the working state for a long time. 8. Regularly clean the seal ring by removing the seal ring, checking whether there is dirt on the shaft, wiping it with a soft cloth, applying a little vacuum grease, and reinstalling it to keep the shaft and seal ring smooth. 9. The electrical part shall be free of water and moisture. 10. Before maintenance, please turn off the power switch and disconnect the power cord from the power supply. 11. The maintenance of internal electric control components and heating components must be operated by professionals or professional electricians. 12. When cleaning the site, do not directly pour water on the product or use grinding powder, thinner, petroleum, kerosene, acidic substances and similar substances, otherwise it will cause electric shock and other accidents. How to Choose a Rotary Evaporator Before choosing a rotary evaporator, it is necessary to clarify some questions, such as how much is distilled at a time, how many samples need to be distilled every day, what solvents are expected to be distilled, what is the boiling point range of solvents, and whether these solvents are flammable, explosive or toxic and harmful. After determining the experimental requirements and the type of solvent to be distilled, the rotary evaporator can be purchased. In fact, six issues need to be considered when choosing a rotary evaporator: 1. Core technology of rotary evaporator Whether the system can maintain a high degree of vacuum under the corrosion of various solvents and in the state of motion is the most important standard to measure the rotary evaporator. It is sealed with Teflon material and glass, which can resist various solvents, has lasting and reliable air tightness, and can maintain a high degree of vacuum above -0.098 MPa. 2. Factors affecting the efficiency of rotary evaporator For machines of the same specification, there are mainly steam temperature, vacuum degree and cooling water temperature. Restricted by the heat resistance of some materials, it is impossible to increase the steam temperature indefinitely during operation, so high vacuum degree and low cooling water temperature are the two main factors to improve efficiency. 3. Difference between vertical condenser and inclined condenser Vertical condensers are becoming popular because of their small footprint. Large capacity evaporators generally use vertical condensers, but there is essentially no difference between the two instruments. 4. Model selection of rotary evaporator 2L, 3 L, 5L machines are suitable for laboratory and small sample test; 5L, 10 L, 20 L are suitable for pilot test; 20 L, 50 L are suitable for pilot test and production, especially for the extraction of materials that need to avoid metal ion pollution. 5. Rotary evaporator and other types of evaporators The rotary evaporator has the advantages of compact structure, high efficiency, rotary vacuum evaporator ,wiped film evaporator, intuitive operation and no metal ion pollution. It is suitable for laboratory, pilot production and extraction of precious materials, and its sealing performance is comparable to that of foreign machines. 6. Selection of vacuum pump We recommend the circulating water vacuum pump resistant to corrosion of various solvents, which can be vacuumized to -0.098 MPa to meet various use requirements. Advantages of Rotary Evaporator 1. All rotary evaporators have a built-in lifting motor, which can automatically lift the flask to the position above the heating pot when the power is off. 2. Due to the centripetal force and friction between the liquid sample and the evaporation bottle, the liquid sample forms a layer of liquid film on the inner surface of the evaporation bottle, and the heating area is large; 3. The force generated by the rotation of the sample effectively inhibits the boiling of the sample. These features, together with their convenience, allow modern rotary evaporators to be used to distill most samples quickly and gently, even by inexperienced operators. Disadvantages of Rotary Evaporator Boiling of certain samples, such as ethanol and water, will result in the loss of the sample collected by the experimenter. During operation, boiling can usually be prevented by carefully adjusting the working intensity of the vacuum pump or the temperature of the heating pot during the mixing stage of the distillation process. Alternatively, anti-boil particles may be adde to that sample. For samples that are particularly difficult to distill, including those that are prone to foaming, the rotary evaporator can also be equipped with a special condenser tube. What are the precautions for using the rotary evaporator? Usage: 1. Turn on the low temperature coolant circulating pump. Note that press the power button and then press the cooling button to start the cycle after the temperature is reduced to the required temperature. 2. Turn on the water pump for circulating water. 3. Install the distillation flask and fix it with a clamp. Turn on the vacuum pump and start to rotate when there is a certain vacuum. 4. Adjust the height and rotation speed of the distillation flask, and set the appropriate water bath temperature. And 5, aft that distillation is finished, stop the rotation, introducing the atmosphere, stopping the water pump, and finally take down the distillation flask. 6. Stop the low-temperature coolant circulating pump, stop the water bath for heating, stop the water pump for circulating water, pour out the solvent in the receiving bottle, and wash the buffer ball and receiving bottle. Caution: 1. When using, first pump a small vacuum (about 0.03 MPa), and then start the rotation to prevent the distillation flask from falling off; when stopping, first stop the rotation, hold the distillation flask by hand, open the atmosphere, and then stop the vacuum pump when the vacuum degree drops to about 0.04 MPa to prevent the distillation flask from falling off and sucking back. 2. Each interface, sealing surface, sealing ring and joint shall be coated with a layer of vacuum grease before installation. 3. Water must be added before the heating tank is powered on, and dry heating without water is not allowed. 4. If the vacuum degree is too low, pay attention to check the air tightness of each joint, vacuum tube and glass bottle. 5. When spinning the air-sensitive substances, connect a nitrogen balloon at the exhaust port, introduce a burst of nitrogen first, discharge the air in the spinning instrument, and then connect the sample bottle for spinning. After steaming, release nitrogen to boost the pressure, then turn off the pump, and then take down the sample bottle and seal it. 6. If the viscosity of the sample is very high, the rotation speed should be slowed down. It is better to rotate slowly manually to form a new liquid level to facilitate the evaporation of the solvent. What are the factors that affect the distillation efficiency of rotary evaporator The distillation efficiency of the rotary evaporator determines the number of samples that can be distilled per day. In the case of the same solvent, the higher the distillation efficiency, the more samples can be distilled. So what are the factors that affect the distillation efficiency of rotary evaporator? 1. Vacuum value of system Vacuum degree is the most important process parameter of rotary evaporator, but users often encounter the problem that the vacuum degree can not be reached. This is often related to the nature of the solvent used. Water, ethanol, acetic acid, petroleum ether, chloroform and other solvents are commonly used in biochemical and pharmaceutical industries. However, general vacuum pumps can not resist strong organic solvents. Special vacuum pumps with strong corrosion resistance can be used. Water circulation vacuum pumps are recommended. Structurally, the enclosed space of the rotary evaporator is composed of glass components such as an evaporation bottle, an evaporation tube, a seal ring, a condenser tube, a vacuum buffer bottle, a vacuum pump and a vacuum pipeline, among which the vacuum pump, the seal ring and the vacuum tube are the most critical and variable factors affecting the vacuum of the system. 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 and avoid bumping. At present, the ultimate vacuum of the diaphragm vacuum pump can be as low as 2mbar, and the ultimate vacuum of the circulating water pump is about 50mbar (0.095 kPa). If the budget allows, a vacuum controller or vacuum valve is necessary to control the system vacuum level required for distillation. Sealing ring: As the key sealing element to receive the evaporation tube and condenser tube, its wear resistance and corrosion resistance are the key. Materials commonly used for sealing rings are PTFE and rubber. Obviously, PTFE has better wear resistance and corrosion resistance. Some manufacturers add stainless steel buffer shrapnel in the seal ring, which has better wear resistance. Vacuum tube material: general manufacturers do not have standard vacuum tube, when they choose and buy, silicone tube is naturally the first 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, but considering the thermal sensitivity of the target component and the safety of operation, the most commonly used temperature is 60 C. Moreover, above 80 ° C, the use of silicone oil as a medium will cause cleaning problems, and it is generally recommended to reduce the vacuum value to achieve faster distillation efficiency. At present, the best diaphragm vacuum pump on the market has a limit vacuum of 2mbar, and DMF can be distilled at room temperature. 3. Rotating speed of evaporation bottle The faster the rotating speed of the evaporation bottle is, the larger the wetting area of the inner surface of the bottle is, and the larger the heated area is; but at the same time, the thicker the liquid film is, and the greater the heat transfer temperature difference is. There is an optimum rotational speed for materials with different viscosities. And that rotation pow is provided by the motor, the DC brushless motor, the AC motor and the step motor are all available on the market, and the feedback of the DC brushless motor is the best, and the motor is maintenance-free for 10 years. 4. Temperature of cooling medium In order to ensure the best distillation efficiency, it is generally recommended to maintain a temperature difference of 40 ° C between the cooling medium and the heating pot temperature, so as to condense the hot steam quickly and reduce the influence of the steam on the vacuum of the system. The biggest disadvantage in the application of rotary evaporator It is the boiling of certain samples, such as ethanol and water, that will result in the loss of the sample collected by the experimenter. During operation, boiling can usually be prevented by carefully adjusting the working intensity of the vacuum pump or the temperature of the heating pot during the mixing stage of the distillation process. Alternatively, anti-boil particles may be adde to that sample. For samples that are particularly difficult to distill, including those that are prone to foaming, the rotary evaporator can also be equipped with a special condenser tube. (Source: Experiment and Analysis) Mumuxili Instrument said that all liquid phase veterans know this. Daily maintenance of pipette: teach you how to disassemble and assemble correctly How to obtain the ideal standard curve? Special statement: The publication of this article is only for the purpose of disseminating information, and does not represent the views of this public account; if other media,thin film distillation, websites or individuals reprint and use from this public account, please apply to the original author, and bear the copyright and other legal responsibilities. Return to Sohu to see more Responsible Editor:. toptiontech.com

Comments