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Water quality standards

For various fields of use and requirements.

International Organization for Standardization (ISO)

ISO 3696:1987 distinguishes between three degrees of purity for water for analytical purposes in laboratories.

ParameterGrade 1Grade 2Grade 3
pH value at 25°C ––5.0 up to 7.0
Conductivity at 25 °C [µS/cm]0.11.05.0
Oxidizable matter, oxygen content [mg/l, max.]–0.080.4
Absorption at 254 nm and a lenght of 1 cm (absorption units, max.) 0.0010.01–
Residue after evaporation by heating to 110 °C (mg/kg, max.) –12
Silicon content [mg/l, max.]0.010.02–

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.

ParameterCLRW
Resistance [MΩ x cm]10
TOC [ppb]< 500
Bacteria [CFU/ml]< 10
Particle ContentInline 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.

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