Laboratory freeze dryer, also known as freeze dryer, is a precision equipment used to remove moisture from thermosensitive samples such as biological, pharmaceutical, and food.The principle is to freeze the sample in advance, and then sublimate the ice directly into water vapor in a vacuum environment to obtain a dried product. This method can maximize the preservation of the physical, chemical properties, and biological activity of the sample. Standardized operating procedures are key to ensuring freeze-drying effectiveness, ensuring equipment safety, and extending instrument lifespan.

　　1、 Pre preparation and sample preparation

1. Sample pretreatment: This is the foundation for successful freeze-drying. Liquid samples should be placed in suitable containers (such as serum bottles, trays), with a loading capacity typically not exceeding one-third of the container depth to increase surface area. For samples that are not easily formed into solids, scaffold agents (such as mannitol, trehalose) can be added. The sample must be pre frozen and placed in an ultra-low temperature freezer or liquid nitrogen at -40 ° C to -80 ° C for rapid freezing, forming uniform ice crystals. Poor pre freezing can cause the sample to melt, bubble, or fail during the drying process.

2. Equipment inspection: Check whether the cold trap chamber of the freeze dryer is clean and free of frost residue. Confirm whether the oil level of the vacuum pump is at 1/2 to 2/3 of the viewing window and the oil quality is clear. Check if the power supply and air pressure source (if they are of the gland type) are connected properly. Ensure that all sealing rings are intact and clean to ensure vacuum sealing.

　　2、 Sample installation and start-up operation

1. Sample loading: Quickly transfer the pre frozen sample from the low-temperature environment to the freeze dryer cold trap or pre cooled sample rack to prevent the sample from melting due to temperature recovery. The operation process should be swift to avoid excessive frosting on the surface of the cold trap, which could affect efficiency. If using a multi manifold type, it is necessary to ensure that the valves at each interface are tightly closed.

2. Start the program: Close the compartment door and ensure a tight seal. To start the device, first activate the cooling function. Wait for the temperature of the cold trap to drop below -50 ℃ (usually up to -60 ℃ to -80 ℃) and stabilize before starting the vacuum pump. This sequence is crucial to prevent the sample from heating up and to prevent water vapor from entering the vacuum pump and causing oil contamination. Observe the vacuum degree until it reaches the limit value required by the equipment (usually 0.1 mbar or below).

　　3、 Process monitoring and end drying

1. Monitoring: Throughout the entire drying process (which may last from several hours to several days), it is necessary to regularly observe and record changes in the cold trap temperature, vacuum degree, and sample appearance. During the primary drying stage (ice sublimation), porous structures can be observed on the surface of the sample; The secondary drying stage (analytical drying) is used to remove bound water, and the sample morphology no longer shows significant changes.

2. Conclusion judgment: Whether the drying is completed can be judged by the following methods: continuously observing multiple times, and the vacuum degree no longer significantly increases; The sample has a full and porous shape, and is basically consistent with its pre freezing shape. After reaching the predetermined program time and meeting the above characteristics, it is ready to end.

　　4、 Sampling and shutdown maintenance

1. Breaking the vacuum and sampling: First, turn off the vacuum pump, and then slowly fill the drying chamber with dry inert gas (such as nitrogen) or air through the inlet valve until the pressure returns to normal. Smoothly open the warehouse door, quickly remove the dried sample, and immediately seal and store it to prevent moisture absorption.

2. Shutdown and maintenance: Turn off the host power. If there is ice accumulation in the cold trap, wait for it to naturally melt, drain and dry the inner cavity. Clean the warehouse body and accessories. Record the usage situation this time. Regularly replace the vacuum pump oil, inspect the sealing ring, and perform maintenance according to the manufacturer's requirements.

By following the standardized process mentioned above, not only can high-quality freeze-dried products be obtained, but the service life of laboratory freeze dryers can also be significantly extended, ensuring the reliability and reproducibility of experimental results.