Ultra pure water:

Ultrapure water: ultrapure water, which not only completely removes the conductive medium in the water, but also removes the non dissociated colloidal matter, gas and organic matter in the water to a very low level. The resistivity is greater than 18m Ω* Cm, or close to 18.3m Ω* Cm limit. Nanopure or milli-q is usually used in the laboratory, and the water source is deionized water or RO water;

Deionized water:

Deionized water: water that removes both anions and anions from water. The ion in water is removed mainly by RO membrane and mixed bed resin. The common water making instrument is millipore elix, but there are still soluble organic matter, such as heat source, so deionized water can not be used as water for injection;

RO water:

RO water: also known as pure water. That is to say, the pore size of the reverse osmosis membrane is generally between 10a and 100A, so it can remove more than 95% of the ionic impurities;

Distilled water:

Distilled water: the water obtained by vaporizing H2O and then condensing the steam can remove most of the pollutants in tap water, but the 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;

Double distilled water:

Double distilled water: distillation-distillation H2O (ddH2O), which is obtained by twice distillation. The content of inorganic salt, organic matter, microorganism, soluble gas and volatile impurities in the water is very low, and the heat source is removed. It can be generally used as water for injection.

According to the order of purity level: ultra pure water, deionized water, double distilled water (ddH2O), pure water (RO water), distilled water.

Ultra pure water can be used for all kinds of experimental water, especially for high sensitivity ICP / MS, PPT analysis, isotope analysis, CDC, Institute for drug control, quality inspection institute, environmental monitoring station, university scientific research and other standard laboratories and various high-end precision instruments. Other pure water and double distilled water can also be used when the requirements are not very strict according to the actual situation（ Note: water for injection refers to distilled water or deionized water after heat source is removed by distillation.)