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Clinical Chemistry and Diagnostics

Laboratory water purification for chemical analyzers and testing

Water purity is crucial in the fields of clinical chemistry and diagnostics. Ongoing developments in the approach to clinical testing and in the sophistication and range of tests available have made water purity even more instrumental.

Poor water quality not only directly affects the tests themselves; it impacts all aspects of analyzer operation. The most challenging aspect of water purification is effective and long-term bacterial control. A high-quality water purification system design is the key to accomplishing this, by providing recirulation through the key purification technologies.

The most challenging aspect of water purification: effective and long-term bacterial control

Clinical Laboratory Reagent Water (CLRW) Standard

The College of American Pathologists (CAP) recommends that all water used for any application in laboratory testing meet the Clinical Laboratory Reagent Water (CLRW) standard specified by the Clinical Laboratory Standards Institute (CLSI) as a minimum. In addition, instrument feed water must meet the instrument manufacturer’s specifications – which may be more rigorous than CLRW standards – to ensure accurate and reproducible results.


The CLRW specification limits four key types of impurity in pure water:

  • Ions - Effectively requires the elimination of carbon dioxide by restricting concentrations of ionic impurities with a resistivity specification of >10MΩ.cm.

  • Particulates - A requirement for all applications is the absence of particulates. Filtration removes particulates inorder to prevent the growth of bacteria and formation of bio-film.

  • Organics - The CLRW calls for Total Organic Carbon (TOC) levels of <500 ppb.

  • Bacterial by-products - Low levels of bacteria is immerative to prevent contamination and ensure proper equipment operation.

Standards for Clinical Laboratory Reagent Water (CLRW) 
Resistivity @ 25°C (megohms-cm) ≥10
Conductivity @ 25°C (micromhos/cm) 0.1
Bacterial Growth (cfu/ml) <10
Organics <500 ppb
Particulate Matter 0.22 ​µm Filter*

*The requirement is a process specification, and not measured by the end-user


Evoqua is your trusted partner for the design and development of laboratory water purification systems for healthcare applications. Our technical experts can help select the right solution to meet CLRW standards and ensure consistent water quality and quantity.

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