I have a 15 mL mixture containing sucrose and a few other substances in a sealed scintillation vial. After some time the cap became distended. I believe it is because sucrose is being oxidized, resulting in generation of carbon dioxide. Anyone have any suggestions about how I can confirm that the gas in the headspace is carbon dioxide? I have a bit of a hurry so I'm looking for something simple, inexpensive, and I don't want to order any sensors or anything.