What is the CFU/mL threshold for Type 1 reagent water?

• A. <10
• B. <100
• C. <1000
• D. Not specified

Answer: (A)

Type of reagent water dictates how many viable microorganisms are allowed per milliliter. Type 1 reagent water is ultrapure and used for the most critical measurements, so its microbial burden is extremely low. The accepted threshold is less than 10 colony-forming units per milliliter. In practice, labs produce Type 1 water with high-purity systems and periodically test with microbial culture methods (plate on nutrient agar, incubate, count colonies). If the count were higher, it would correspond to Type 2 or Type 3 water, which have looser limits (less than 100 or 1000 CFU/mL, respectively). Not specified would not meet the requirement for Type 1 water.