Freeze-drying technology Freeze-drying is the process of making the protein sample solution in a state of pre-freezing, using vacuum, without sublimation, to directly sublimate, remove the water content, and make the sample protein into a dry preparation. In immunoenzyme technology, the serum and enzyme used are easily denatured and spoiled in solution. After being prepared as a dry preparation, they can be stored at room temperature or in a refrigerator (4 ° C) for a long time without inactivation, and are easy to carry. The reason for freezing is that the moisture content or solvent of the dried sample increases the evaporation rate due to the reduction of the surrounding air pressure, and the higher the degree of vacuum, the lower the boiling point of the solution, the faster the evaporation. Compared with vacuum drying and spray drying, freeze vacuum drying is more commonly used in experiments. Procedure for freeze-drying serum First, pour the appropriate amount of serum into a petri dish of appropriate size (preferably the thickness of the sample solution is below 1cm), and freeze to a solid state at a low temperature-below 20 ℃. In the freeze-drying device, solid sodium hydroxide and phosphorus pentoxide are placed separately, and the upper suction pipe of the vacuum dryer is connected to the vacuum pump through the phosphorus pentoxide drying pipe. Put the frozen serum block together with the petri dish into the vacuum desiccator, close the desiccator immediately (coat petroleum jelly on the cover edge in advance), and start the oil pump, usually after 5-10 hours, the freeze-dried preparation can be obtained. Freeze drying is complete. First, gradually open the glass valve on the top cover of the dryer, and slowly deflate. After the pressure in the entire system rises to atmospheric pressure, remove the sample drying container, and finally turn off the vacuum oil pump. 2. Discussion (1) The effect of freeze-drying depends on the vacuum degree of the vacuum pump and the appropriate pipe diameter. The vacuum oil pump is best to use a large evacuation capacity, and all the connecting pipes should be thick and short. (2) If the sample is a solution, it is best to use an aqueous solution to avoid the organic solvent lowering the freezing point and entering the pump. The concentration should be moderate, not less than 1.5%. If the sample uses a buffer as a solvent, it is best to use a volatile buffer such as carbonate or acetate; if it is non-volatile, the influence of pH and salt concentration on the sample must be considered. For example, with pH 7.0 phosphate buffer, the Na2 salt crystallizes earlier than the Na salt during freeze-drying, and the pH drops to about 3.5, which is harmful to the sample. Adding a small amount of gelatin, lactose or glucose to the sample solution is conducive to preserving activity. When pre-freezing the sample, it is best to put it in an ordinary refrigerator to cool to 0 ℃, and then quickly move it into a refrigerator below 20 ℃ to freeze and freeze. When the vacuum is evacuated, if the sample melts, it must be re-frozen and the cause must be checked. Vacuum for about 30 minutes. If the container containing the pre-frozen sample is frosted, it indicates a good operation. Due to the sublimation of the moisture in the sample, the temperature is reduced, the sample is naturally in a frozen state, and there is no need to take cooling measures outside the dryer. The dried preparation is packed in vials, sealed with wax, and stored in an ordinary refrigerator. Salad is now more and more popular with young people, and the corresponding tableware is also becoming more and more important. Salad Fork is one of them. Although we can also use toothpicks or disposable forks instead, from the perspective of environmental protection, we still suggest using reusable salad forks. Our salad spoon is lovely, interesting and environmentally friendly, and can be matched with colorful fruits and vegetables. It can be used at home or in restaurants, hotels and other places. Salad Fork Salad Fork,Salad Fork Set,Metal Salad Fork,Stainless Steel Salad Fork Jieyang Huiyi Hardware Products Co., Ltd. , https://www.chinagdhuiyi.com
Our salad spoon has a smooth surface and feels very comfortable to hold in hand. Every product, from design to workmanship, strives for perfection. Let's turn dining into a kind of enjoyment together.