Abstract: An analytical rotor for separating plasma whole blood comprises a rotor body having a sample application port in an upper surface thereof. Blood introduced to the sample application port is metered into a metering chamber by capillary flow while the rotor remains stationary. Excess blood passes into an overflow chamber by capillary flow, either simultaneously with the metered flow or after opening of a vent in the overflow chamber. Subsequent rotation of the rotor causes metered blood in the metering chamber to flow into a receiving chamber, typically a plasma separation chamber.