Vacuum freeze-drying principle
First, why is the thymopentin for injection not directly heated or dried, but vacuum freeze-dried?
Vacuum freeze-drying is carried out below 0 ° C under vacuum conditions, vacuum freeze-dried and injected with thymopentin volume
It is unchanged, loose and porous, and has good resolubility. The heat-sensitive substance is not easy to be destroyed; generally, drying cannot be achieved.
Second, the principle of vacuum freeze drying
Vacuum freeze-drying means freezing the drug solution at a low temperature (pre-freezing temperature should be lower than the eutectic point), then heating it under vacuum to perform sublimation drying (heating temperature cannot exceed the eutectic point), removing ice crystals, after the sublimation is over Further, desorption drying is carried out to remove a part of the combined method of drying water.
Third, the vacuum freeze drying procedure
1. Firstly freeze the freeze-drying box and empty the box. Pack the products that need to be lyophilized in a suitable container, usually a glass bottle or an ampoule. The volume should be uniform, the evaporation surface should be as large as possible and the thickness should be as thin as possible; then Put in the freeze-drying box.
2. The product placed in the freeze-drying box is pre-frozen and vacuumed. When vacuuming, the condenser should reach a temperature of about -40 °C. After the vacuum reaches a certain value (usually should reach a vacuum of 100 uHg or more), Can heat the products in the box
3, the general heating is carried out in two steps, * step heating does not make the temperature of the product exceed the temperature of the eutectic; after the water in the product is basically dry, the second step is heated, then the product can be quickly raised Zui high temperature. After a few hours at the high temperature of zui, the lyophilization can be ended.
4. The whole sublimation drying time is about 12-24 hours, which is related to the quantity of the product in each bottle, the total capacity, the shape and specifications of the glass container, the type of the product, the freeze-drying curve and the performance of the machine.
5. After lyophilization, dry and sterile air should be placed in the drying oven, and then sealed as soon as possible to prevent re-absorption of moisture in the air.
Fourth, the advantages of vacuum freeze drying:
1. Freeze-drying is carried out at low temperatures and is therefore particularly suitable for many heat-sensitive substances.
2. When drying at low temperatures, some of the volatile components in the material are lost.
3. The growth of microorganisms and the action of enzymes cannot be carried out.
4. The volume is almost constant, the original structure is maintained, and no concentration occurs.
5. The dried material is porous and spongy, and dissolves quickly and completely after adding water.
6. Drying is carried out under vacuum and some easily oxidizable substances are protected.
7. Drying can exclude more than 95-99% of water.
Five, vacuum freeze drying disadvantages:
The cost of freeze drying is high (both investment and operating costs are high).
Long freeze-drying time and long production cycle.
Six, the key concepts in the vacuum freeze drying process
Eutectic temperature
2. Co-dissolution temperature
Eutectic temperature: When the temperature of a solution reaches a certain temperature, its liquid state and the components in the formed solid are exactly the same, and the temperature at this time is called the eutectic temperature.
Generally, the pre-freezing process should be lower than its eutectic temperature by 10-20 °C.
What is the eutectic temperature of water?
Seven, five important stages of the freeze-drying process
Liquid preparation
Prefreeze
Sublimation drying stage (*dry stage)
Analytical drying stage (second drying stage)
Sealed and stored (embossed or barrel sealed)
Freeze drying process:
7.1 Pre-freezing
Pre-freezing is to bring the solution below the eutectic point for sublimation under a certain degree of vacuum.
If the product is not frozen, the product boils and emerges from the bottle when vacuuming;
If the product temperature is too cold, it does not waste energy and time, and it also reduces the survival rate of the product.
7.2 Freezing method
Quick freezing: In order to form microcrystals, the obtained product has a good appearance and a fast dissolution rate.
Slow freezing: The formation of coarse crystals improves the lyophilization efficiency, but slow freezing is unfavorable for the survival of some active enzymes or live bacteria.
7.3 * Drying stage
Sublimation drying is also known as *stage drying. The frozen product is heated in a sealed vacuum vessel, and the ice crystals are sublimated into water vapor to escape and the product is dehydrated and dried.
* Stage sublimation drying is a critical stage of freeze drying, and most of the water is sublimed at this stage.
If the control is not good, it will directly affect the appearance quality and freeze-drying time of the product.
If the temperature of the shelf is too high, the heat supplied by the shelf to the product is greater than the heat absorbed by the sublimation of the moisture, the temperature of the product continues to rise, and when the temperature of the product exceeds its eutectic point, the spray bottle or the bottom of the bottle becomes empty. Affect the appearance quality of the product.
7.4 Second drying stage (analytical drying stage)
Analytical drying is also referred to as the second stage of drying. After the end of the * stage drying, about 10% of the moisture in the product is adsorbed on the capillary wall and the polar group of the dry substance, and this part of the water is not frozen.
Therefore, in order to improve the storage stability of the product and prolong its shelf life, it is necessary to remove the moisture. This is the purpose of analytical drying.
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