Introduction to Ultrapure Deionized Water

High purity water is critical to laboratory, analytical and R&D work.

Ultrapure Water Definition

Ultrapure water (UPW) is water that has been purified to very strict specifications, containing by definition only H₂O, and H⁺ and OH^- ions in equilibrium. Therefore, ultrapure water conductivity is about 0,055 uS/cm at 25oC, also expressed as resistivity of 18,2 MOhm - cm. It usually contains mostly pure H₂O, H⁺ and OH^- ions.

Ultra Pure Water is of very high purity that's designed to be as close to pure H2O as possible. A lot of impurities, not only dissolved solids (TDS), but salts and gases are removed. Water cannot stay in this state for a long periods of time as it is seeking to balance itself from the environment.

Read more here, Water Quality Standards document (pdf)