The correct operating steps for a desktop freeze dryer are as follows:
1、 Preparation before startup
1. Equipment inspection: Confirm that the oil level of the vacuum pump is at 2/3 of the window, and that the sealing ring is intact and undamaged.
2. Sample pretreatment: Freeze the liquid sample into a solid state at -80 ℃ in a refrigerator, and spread the solid sample evenly.
2、 Pre freezing stage
1. Start cooling: Press the "cooling" button on the touch screen to lower the temperature of the cold trap to below -40 ℃ (-60 ℃ is required for biological samples).
2. Loading samples: Place the pre frozen samples in a drying rack, quickly transfer them above the cold trap, and cover them with an organic glass cover.
3、 Vacuum drying
1. Vacuum pumping operation: Close the inflation valve, start the vacuum pump, and observe that the vacuum degree drops below 10Pa.
2. Process monitoring: If the vacuum degree is abnormal, check the oil level or sealing (if the rubber ring leaks, it needs to be replaced).
4、 End and maintenance
1. Vacuum breaking treatment: First, turn off the vacuum pump and slowly open the inflation valve until the air pressure is balanced.
2. Cleaning and maintenance: After defrosting, clean the accumulated water in the cold trap and wipe the organic glass cover with a damp cloth (alcohol is prohibited).
5、 Key precautions
1. Sequential requirement: The sample must be pre frozen before vacuuming to avoid melting.
2. Safety interval: Continuous startup should be separated by at least 10 minutes to protect the compressor.
3. Special samples: Porous materials need to be perforated in the sealing film to promote sublimation.