Lab applications require different grades of water purity. For example, rinsing equipment, mass spectrometry and IVF all require different types of ultrapure water. Even minimal traces of contaminants can adversely affect sensitive analytical measurements; the accuracy of many tests depends heavily on the use of the correct type of water. "Water quality that is below the accepted standards not only affects the chemistry of the tests but can also affect the general operation of the analyzer." (Medical Laboratory Observer)
According to ASTM Standards for Laboratory Reagent Water, there are four main types of lab water (ASTM D1193-91).
Type 1 (Ultrapure) : is used for advanced analytical procedures and critical applications such as:
Type 2 (General grade lab water) : is used in general lab and clinical practices such as
Type 3 (RO water) : is the starting point of water for many non-critical laboratory applications
Type 4 (RO water) : is the starting point of water for many non-critical laboratory applications such as:
|Parameter||Type I*||Type II||Type III ***||Type IV|
|Conductivity (uS/cm) at 25, max||0.056||1.0||0.25||5.0|
|Resistivity (Mohms-cm), max||18.0||1.0||4.0||0.2|
|pH at 25C||-||-||-||5 to 8|
|TOPC (ug/l), max||50||50||200||no limit|
|Sodium (ug/l), max||1||5||10||50|
|Silica (ug/l), max||3||3||500||no limit|
|Chloride (ug/l), max||1||5||10||50|
It is critical to know the types of water that are needed, the top flow rate and the peak laboratory demands when selecting the correct water purification system for a laboratory. Underestimating lab water needs can be very costly in terms of downtime and the loss of experiments.