I will be collecting and transporting microbial swab samples in a region of the world without reliable access to dry ice. Samples will be used for Illumina sequencing. Usually, I transport frozen samples from my field site to my university on dry ice. However, I will not have access to dry ice on my upcoming trip and samples will need to be out of the freezer for up to 10 hours during periods of transport from one field site to another.
Does anyone have any clever tricks to keep small volume (~1ml) samples frozen during transit? For example, might freezing the eppendorf tubes inside a block of ice in a styrofoam cooler work? I've tried using a cheap portable freezer but it didn't reliably keep temperature and the samples thawed and refroze, which is really problematic. Thanks for any suggestions!
Stacey Weiss
Take with you solutions that lower the temperature after mixing and use them instead of ice. For example, H2SO4, 44.55% + Na2SO4, 55.5% lowers the temperature to -20 0С.
For a 10h trip, the styrofoam box is effective. Place ice at the bottom of the styrofoam box, position the Eppendorf tube in the center, and cover it with additional ice. Seal the styrofoam box tightly, preferably using silicone gum to ensure the opening is completely sealed.
But, the best option is to use a hot water bottle. It will conserve the ice better than a styrofoam box and you can keep the ice for a extended period.