4 °C is the most common storage temperature for environmental and water samples, but it does not fit every sample. In EPA's US emergency drinking water guidance volatile organics, carbamates and cyanide are stored below 4 °C, pathogen samples below 10 °C without freezing; metals are preserved with nitric acid, and Vibrio cholerae travels at room temperature.
A sample that needs cooling travels with ice in double water-tight bags placed between and on top of the bottles. Bottles must not touch, and a temperature blank goes beside them. Get the method's target temperature, container type and acceptance time from the laboratory before sampling.
Time matters as much as temperature: the same table gives holding times of 14 days for volatile organics and cyanide, 28 days for carbamates and 24-30 hours for bacterial samples such as E. coli.
Record the sample code, location, date and time, the collector and the chain-of-custody form; report any delay or temperature deviation to the laboratory.
