Devices and methods of dispensing and mixing reagents with samples in an enclosed container in which the amounts of the reagents dispensed into the sample are predetermined. The devices include a rotating dispenser element attached to a base, wherein an ampoule is located within a cavity in the base. The dispenser elements contain two or more dispensing chambers that are sealed and that can be opened and any reagent(s) located therein dispensed into the ampoule at selected times.