Zinc oxide is the metal zinc that has been oxidized. The chemical formula is ZnO, 1 zinc atom and 1 oxygen atom held together by an ionic bond. Zinc oxide does occur in nature as the mineral zincite, but it is quite rare and commercially unavailable.
I have done a few stool samples in my time and have always just stored them in the fridge, until the next day to take them into the docs. Good luck hun I hope they get it sorted.
At refrigerator temperatures, that is, 32 degrees F to 40 degrees F, bacteria can still grow, but that growth is slowed dramatically. That's why you must use raw perishable food within a certain time frame, usually 2-3 days, even when it is properly refrigerated.