The production of high-purity water in the clinical laboratory

As the sensitivity and variety of tests increase, the types and tolerable concentrations of impurities that may inhibit clinical tests become an increasing concern. Because water constitutes a high percentage of the buffers and reaction mixtures used in clinical assays, the use of high-purity water is critical for reliable, consistent, and cost-effective laboratory analysis. A wide range of contaminants exists in potable water supplies and must be removed with a water system containing the proper combination of specific purification technologies. Technologies such as activated carbon, reverse osmosis, ion exchange, and distillation have particular purification capabilities and must be selected based on their ability to consistently produce water with purity suitable for specific test methods. The National Committee for Clinical Laboratory Standards (NCCLS) provides guidelines for the production and use of purified water in the laboratory. The production of reagent water that meets the NCCLS guidelines requires proper measurement and monitoring of contaminant level in both incoming source water and product reagent water The introduction of new diagnostic tests requires the removal and monitoring of contaminants, such as nucleases and extraneous DNA, and creates new criteria for water purity and water system design. Current water purification technologies are reviewed, and a system designed to provide type I water is discussed.