Water used as a reagent in the clinical laboratory can be classified based on its composition. Only water of the specified type should be used for a laboratory proceedure.
Parameter
Type I
Type II
Type III
maximum microbial content, in CFU/mL
10
1000
not specified
pH
not specified
not specified
5.0 - 8.0
minimum resistivity in megohm • cm at 25°C
10 (inline)
1.0
0.1
maximum silicate in mg/L SiO2
0.05
0.1
1.0
particulate matter
0.22 µm filter
not specified
not specified
organic contaminants
activated carbon, or distillation, or reverse osmosis
not specified
not specified
where:
• CFU/mL = colony forming units per mL
• resistivity defines the allowable ionic content of the water
• particulate matter and organic contaminants are purification process requirements and are not measured by the end user.
Note: The American Chemical Society (ACS) has published specifications for Reagent and Analytical Reagent (AR) Grade water. These may be either directly analyzed for impurities or have specified maximum allowed limits for each impurity.
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