International Organization for Standardization (ISO)
ISO 3696:1987 distinguishes between three degrees of purity for water for analytical purposes in laboratories.
pH value at 25°C
Conductivity (µS/cm at 25 °C)
oxygen content (mg/l, max.)
Absorption at 254 nm
and a lenght of 1 cm
(absorption units, max.)
Residue after evaporation by heating to 110 °C (mg/kg, max.)
Silicon content (mg/l, max.)
Clinical Laboratory Standards Institute (CLSI)
This institute defined the quality requirements of water for clinical laboratories. The regulations that were valid up to 2006 (NCCL types 1, 2 and 3) but were then invalidated by the requirement that water must be suitable for the intended usage. Only the degree of purity of so-called “Clinical laboratory reagent water” (CLRW) is described.
10 MΩ x cm
< 500 ppb
< 10 CFU/ml
Inline 0.2 µm-filter
American Society for Testing and Materials (ASTM)
The ASTM D1193-06 (2011) deals with the requirements for chemical analyses and physical tests.