Ultrapure water
Ultrapure water is specially purified water. In contrast to conventional water , as it occurs in nature and which z. B. contains minerals such as magnesium , ultrapure water contains almost no foreign substances.
definition
The European Pharmacopoeia places the following requirements on highly purified water ( Aqua valde purificata ):
- Conductivity ≤ 1.1 μS / cm at 20 ° C
- Bacterial endotoxins <0.25 IU / ml (corresponds to around 25 ng / l)
- Total organic carbon (TOC) ≤ 0.5 mg / l
- Nitrate ≤ 0.2 mg / l
This so-called ultra-pure water (URW) is primarily determined by its TOC limit value, while ultrapure water for technical applications manages with a TOC value of ≤ 1 mg / l.
There are differences between the quality of distilled water , demineralized water and ultrapure water, which can be seen particularly in the electrical conductivity . The conductivity is given in the unit S / m , in technical parlance it is almost always given in µS / cm. Since the water molecule is an ampholyte that can react with itself, even ultrapure water has a low electrical conductivity. The calculated limit value is 0.055 µS / cm at 25 ° C, corresponding to a resistance of 18.2 MΩcm (mega-ohms times centimeters). In ultrapure water technology, the resistance of the water is mostly used as a quality feature. The value for distilled water is between 0.5 and 5 µS / cm at 25 ° C.
According to ISO 3696, water for analytical purposes may have a maximum conductivity of 0.1 µS / cm at 25 ° C in quality 1.
In the case of water for the manufacture of drugs that are administered to the human body, at least purified water (e.g. non-sterile liquids that are taken orally ), and for the manufacture of parenterals (e.g. infusions ) water for injections (WFI ) required. Among other things, the European Pharmacopoeia regulates the amount of organic components that can consist of cell debris and proteins .
Water for steam generation in power plants with high pressure steam generators may have a maximum conductivity of 0.2 µS / cm.
Manufacturing
The most common process for the production of ultrapure water is reverse osmosis , less often distillation . Both processes are combined with other cleaning processes such as ion exchangers , activated carbon filters , ultrafiltration , photooxidation , degassing processes (vacuum degassing, membrane degassing), disinfection by UV radiation, electrochemical deionization .
use
Ultrapure water is required in many areas. Essentially, these are the manufacture of drugs , for injection liquids , in medical research, in chemical analysis, in the manufacture of integrated circuits (ICs; see photolithography and solar cells ).
In water for the production of parenterals but water for injections required.
Individual evidence
- ↑ ultrapure water
- ↑ Herbert Bendlin: Ultrapure water: planning, qualification and operation of ultrapure water systems. Verlag Maas & Peither GMP, ISBN 978-3934971097 .