At what temperature must the water sample be refrigerated?

For water samples, particularly those intended for microbiological testing, it is important to maintain a temperature that preserves the integrity of the sample. Refrigeration at 39 degrees Fahrenheit is recognized as optimal for slowing down any biological activity without freezing the sample. This temperature helps to minimize the growth of bacteria while still being above freezing point, where ice crystals could damage the cellular structures of microorganisms, potentially skewing the test results.

In many water sampling protocols, especially those related to drinking water and environmental samples, 39 degrees Fahrenheit is a standard recommendation. This temperature is also consistent with guidelines set by regulatory agencies that govern water quality testing, ensuring that sample analysis reflects the true conditions of the water source and adheres to best practices in sampling methodology.