The production of high-purity water in the clinical laboratory

As the sensitivity and variety of tests increase, the types and tolerable c oncentrations of impurities that may inhibit clinical tests become an incre asing concern. Because water constitutes a high percentage of the buffers a nd reaction mixtures used in clinical assays, the use of high-purity water is critical for reliable, consistent, and cost-effective laboratory analysi s. A wide range of contaminants exists in potable water supplies and must b e 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 capabi lities and must be selected based on their ability to consistently produce water with purity suitable for specific test methods. The National Committe e for Clinical Laboratory Standards (NCCLS) provides guidelines for the pro duction and use of purified water in the laboratory. The production of reag ent water that meets the NCCLS guidelines requires proper measurement and m onitoring of contaminant level in both incoming source water and product re agent water The introduction of new diagnostic tests requires the removal a nd monitoring of contaminants, such as nucleases and extraneous DNA, and cr eates new criteria for water purity and water system design. Current water purification technologies are reviewed, and a system designed to provide ty pe I water is discussed.