Water is a reagent that is often overlooked but vital in the laboratory. What types of laboratory water are available? What level can it reach? What are the water requirements for different experiments? These problems used to have some vague concepts for me. I participated in the tender for the pure water installation of the school a few days ago, read some relevant materials, and learned the relevant knowledge initially. Now I will share it with you, most of them are I have translated it from foreign language materials, and I hope you will criticize it if it is inappropriate. These materials also include the essence of freecell comrades in this section, thank you!
Common types of water in the laboratory:
1. Distilled Water:
The most commonly used pure water in the laboratory, although the equipment is cheap, but extremely energy-consuming and water-consuming and slow, the application will gradually decrease. Distilled water can remove most of the contaminants in tap water, but volatile impurities such as carbon dioxide, ammonia, silica, and some organic matter cannot be removed. Fresh distilled water is sterile, but bacteria are prone to multiply after storage. In addition, the storage container is also very particular. If it is a non-inert substance, the ions and the shaping material of the container will precipitate to cause secondary pollution.
2. Deionized Water:
Ion exchange resins are used to remove anions and cations in water, but there are still soluble organics in the water, which can contaminate the ion exchange column and reduce its effectiveness. Deionized water can also easily cause the reproduction of bacteria.
3. Reverse osmosis Water:
The principle of its generation is that water molecules become pure water through the reverse osmosis membrane under the action of pressure, and impurities in the water are trapped and discharged by the reverse osmosis membrane. Reverse osmosis water overcomes many shortcomings of distilled water and deionized water. Reverse osmosis technology can effectively remove dissolved salts, colloids, bacteria, viruses, bacterial endotoxins and most organic impurities in water, but reverse osmosis membranes produced by different manufacturers It has a great influence on the quality of reverse osmosis water.
4. Ultra-pure grade water:
The standard is that the water resistivity is 18.2MΩ-cm. However, ultrapure water is not the same in terms of TOC, bacteria, endotoxin and other indicators. It should be determined according to the requirements of the experiment. For example, cell culture requires bacteria and endotoxin, while HPLC requires low TOC.
Common indicators for evaluating water quality:
1. Electrical resistivity:
The unit for measuring the electrical conductivity of laboratory water is MΩ-cm. As the inorganic ions in the water decrease, the resistance increases and the value gradually increases. The standard for ultrapure water in the laboratory: the resistivity is 18.2MΩ-cm.
2. Total Organic Carbon (TOC):
The concentration of carbon in water, reflecting the content of oxidized organic compounds in water, is expressed in ppm or ppb.
3. Endotoxin:
The cell wall fragments of lipopolysaccharides of Gram-negative bacteria, also known as "pyrogens", are in units of cuf / ml.
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