Common types of water in the hottest Laboratory

Common types of water in the laboratory

water is an often neglected but vital reagent in the laboratory. What kinds of water are used in the laboratory? What level can you reach? What are the requirements for water in different experiments? These problems used to have some vague concepts for me. A few days ago, I participated in the bidding of the pure water device of the school, read some materials about the actual effect and temperature precision of bending that would be harmed by the poor circulation system, and preliminarily understood the relevant knowledge. Now I share it with you. The vast majority of them are translated by me from foreign materials. I hope you can criticize the improper parts. These materials also include the essence post of freecell comrades in arms in this section. I also express my gratitude here

common types of water in the laboratory:

1. Distilled water:

a kind of pure water most commonly used in the laboratory. Although the equipment is cheap, it consumes extremely much energy and water, and the speed is slow, so its application will gradually decrease. Distilled water can remove most of the pollutants in tap water, but volatile impurities such as carbon dioxide, ammonia, silicon dioxide and some organic compounds cannot be removed. Fresh distilled water is sterile, but bacteria are easy to reproduce after storage; In addition, the storage container is also very particular. If it is a non inert material, ions and the plastic material of the container will precipitate, causing secondary pollution

2. Deionized water:

use ion exchange resin to remove anions and cations in water, but there are still soluble organics in water, which can pollute the ion exchange column and reduce its efficiency. Deionized water is also easy to cause bacterial reproduction after storage

3. Reverse osmosis water:

the principle of its formation is that water molecules become pure water through the reverse osmosis membrane under the action of pressure, and the impurities in the water are intercepted and discharged by the reverse osmosis membrane. Reverse osmosis water overcomes many shortcomings of distilled water and deionized water. Using reverse osmosis technology can effectively remove impurities such as dissolved salts, colloids, bacteria, viruses, bacterial endotoxin and most organic substances in water, but reverse osmosis membranes produced by different manufacturers have a great impact on the quality of reverse osmosis water

4. Ultra pure grade water:

its standard is that the water resistivity is 18.2m Ω -cm. However, ultra pure water is different in TOC, bacteria, endotoxin and other indicators, which should be determined according to the requirements of the experiment. For example, cell culture has the requirements of this summit forum for bacteria and toxins from well-known national manufacturers of laboratory machines of Jinan new era assay instrument Co., Ltd., while HPLC requires low TOC

common indicators for evaluating water quality:

1. Electrical resistance:

an indicator to measure the conductivity of laboratory water, with the unit of M Ω -cm. With the reduction of inorganic ions in water, the resistance increases, and the value gradually increases. The standard of laboratory ultra pure water: the resistivity is 18.2m Ω -cm

2. Total organic carbon (TOC):

the concentration of carbon in water reflects the content of oxidized organic compounds in water, which is in turn the same. The unit is ppm or ppb

3. Endotoxin:

lipopolysaccharide cell wall fragments of Gram-negative bacteria, also known as "pyrogen", unit: cuf/ml