I guess I don't see how it contaminates it. its the same liquid used for the same thing. of course they don't want you to try and use it because they you wouldn't have to buy a new bottle as quick. I understand that the air cuts down on the shelf life but I don't think 1/3 of a bottle would make a big difference. especially if you were testing more than the minimum.no, It's been stated that pouring the rest of the reagent bottle into the next will contaminate it.