In one arrangement, a cartridge includes a cartridge body defining a holding compartment, first and second fractioning compartments, and a number of flow channels formed within the cartridge body. A predetermined quantity of fluid can be held in the holding compartment when the cartridge body is held in a first orientation, and can be poured from the holding compartment to the first fractioning compartment by rotating the cartridge body about a predefined rotation axis to a second orientation, spilling the fluid from the holding compartment to the first fractioning compartment through one of the flow channels. The first fractioning compartment is such that when the cartridge body is in the second orientation, not all of the fluid can be contained in the first fractioning compartment, and fluid that overflows the first fractioning compartment flows through a second flow channel to the second fractioning compartment.