How long can samples to be tested for coliforms be refrigerated before analysis?

• A. 4 hours
• B. 6 hours
• C. 8 hours
• D. 10 hours

Answer: (C)

For testing coliforms in water samples, it is critical to preserve the integrity of the samples to ensure accurate results. When refrigerated, coliform samples can typically be held for up to 8 hours before analysis. This time frame is established based on scientific research which indicates that coliform bacteria populations can change if samples are stored for longer durations, potentially leading to inaccurate conclusions about water quality.

Storing samples for more than 8 hours may allow for the die-off or growth of bacteria, which would affect the concentration levels observed upon analysis. It is vital to perform the tests as soon as possible after collection, but when unavoidable delays arise, refrigeration for up to 8 hours is seen as an acceptable practice to maintain the reliability of the sample for coliform testing.