Feed mill laboratory scientific water must learn knowledge
Water is a frequently overlooked but vital reagent in the laboratory. What types of water are used in the laboratory? What level can it reach? What are the water requirements for different experiments? To clarify these vague concepts, forward this .
First, the type of water commonly found in the laboratory:
1. Distilled Water:
The most commonly used pure water in the laboratory, although the equipment is cheap, but extremely energy-intensive and water-consuming and slow, the application will gradually decrease. Distilled water can remove most of the pollutants in the tap water, but the volatile impurities can not be removed, such as Carbon dioxide, ammonia, silica and some organic matter. Fresh distilled water is sterile, but the bacteria are easy to reproduce after storage. In addition, the storage container is also very particular. If it is a non-inert substance, the ions and the shaped material of the container will precipitate. Cause secondary pollution.
2, Deionized Water:
Ion exchange resin is used to remove anions and cations from water, but there are still soluble organic substances in the water, which can contaminate the ion exchange column and reduce its efficiency. It can also cause bacterial growth after deionized water storage.
3. Reverse osmosis Water:
The principle of the formation is that under the action of pressure, the water molecules become pure water through the reverse osmosis membrane, and the impurities in the water are intercepted and discharged by the reverse osmosis membrane. The reverse osmosis water overcomes many shortcomings of distilled water and deionized water, and can be effectively utilized by reverse osmosis technology. The removal of dissolved salts, colloids, bacteria, viruses, bacterial endotoxins and most organic impurities in water, but the reverse osmosis membrane produced by different manufacturers has a great impact 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, etc. It should be determined according to the requirements of the experiment. For example, cell culture requires bacteria and endotoxin. HPLC requires a low TOC.
Second, the commonly used indicators to evaluate water quality:
1. Electrical resistivity:
The index for measuring the conductivity of water in the laboratory, the unit is MΩ cm. As the resistance of the inorganic ions in the water decreases, the value gradually increases. The standard of laboratory ultrapure water: the resistivity is 18.2MΩ cm.
2, Total Organic Carbon (TOC):
The concentration of carbon in water reflects the content of organic compounds oxidized in water, in ppm or ppb.
3, endotoxin (Endotoxin):
The lipopolysaccharide cell wall fragments of Gram-negative bacteria, also known as "pyrogens", in units of cuf/ml.
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