Laboratory pure water what standard?

Overview of ultrapure water for laboratory use Ultrapure water for laboratory use has high requirements for water quality, according to different applications can be divided into three levels of water: a water, resistance requirements greater than 10MΩ.cm (conductivity less than 0.1us/cm), mainly used for analytical tests with stringent requirements, including the requirements for particles in the test. Such as high-pressure liquid chromatography analysis of water. Primary water is commonly used in secondary water after quartz equipment distillation or reverse osmosis and ion exchange mixed bed treatment, and then filtered through a 0.2μm microporous membrane to produce. Secondary water, resistance requirements greater than 10MΩ (conductivity less than 0.1us/cm), mainly used for inorganic trace analysis and other tests, such as atomic absorption spectrometry analysis of water. Secondary water can be used for multiple distillation or reverse osmosis and ion exchange and other methods of production. Tertiary water, tertiary water for general chemical analysis tests. Tertiary water can be distilled or ion exchange and other methods of preparation. Preparation of laboratory water commonly used methods 1, distilled water, the most commonly used in the laboratory of a pure water, although the equipment is cheap, but extremely energy-consuming and water-consuming and slow, the application of the gradual decrease. Distilled water can remove most of the pollutants within the tap water, but volatile impurities can not be removed, such as carbon dioxide, ammonia, silica and some organic matter. Fresh distilled water is sterile, but after storage, bacteria are easy to reproduce; in addition, the storage container is also very careful, if the non-inert material, ions and containers of plastic substances will precipitate causing secondary pollution. 2, deionized water: the application of ion exchange resin to remove anions and cations in the water, is a long time to use a traditional process used to produce pure water, after treatment to obtain a certain degree of purity of ultrapure water, but there are still soluble organic matter in the water can be contaminated with ion exchange columns to reduce its effectiveness, deionized water is also prone to cause bacterial reproduction after storage. 3, reverse osmosis water: the principle of its generation is water molecules under pressure, through the reverse osmosis membrane into pure water, water impurities are retained by the reverse osmosis membrane discharge. Reverse osmosis water to overcome many of the shortcomings of distilled water and deionized water, the use of reverse osmosis technology can effectively remove the dissolved salts in the water, colloids, bacteria, viruses, bacterial endotoxins and most of the organic matter and other impurities. 4, ultrapure water: its standard is the water resistivity of 18.2MΩ-cm. production of ultrapure water, the latest process often used reverse osmosis and ion exchange mixed bed or reverse osmosis and electrodeionization (EDI) to produce, and the latter relative to the former more economical and environmentally friendly. China's national laboratory water specifications GB6682-92 standard PH 25 ℃ conductivity 25 ℃ μS/cm specific resistance 25 ℃ MΩ * cm oxidizable material to (O) mg / L Absorbance 254nm,1cm evaporation residue mg / L (105 ± 25 ℃) soluble silicon to (sio2), mg / L Grade I - ≤ 0.1 ≥ 10 ≥ 10 ≥ 10 ≥ 10 ≥ 10 ≥ 10 ≥ 10 - ≤0.1 ≥10 -- ≤0.001 -- ＜0.01 Grade II -- ≤1.0 ≥1 ＜0.08 ≤0.01 ≤1.0 ＜0.02 1.0 ＜0.02 Tertiary 5.0-7.5 ≤5.0 ≥0.2 ＜0.40 -- ≤2.0 -- China's National Laboratory Water GB6682-2000 Standard Name First grade Second grade Third grade pH range (25℃) --- --- 5.0-7.5 Conductivity (25℃),ms/m ≤0.01 ≤0.10 ≤0.50 Specific Resistance ( 25℃,MΩ,cm) ≥10 ≥1 ≥0.2 Oxidizable substance (in O) mg/L --- ＜0.08 ＜0.40 Absorbance (254nm,1cm light range) ≤0.001 ≤0.01 --- --