Abstract: Devices and methods are provided that permit efficient and selective separation of liquid biological specimens into at least two constituent components to facilitate subsequent quantitative and qualitative analysis on at least one analyte of interest in at least one of the components. For example, a liquid biological specimen separation device includes a base defining a base surface, a collection housing extending away from the base surface to a collection end, a collection membrane disposed on the collection housing adjacent the collection end, and a cap assembly secured to the collection housing. The cap assembly includes a cap defining an aperture therein configured to allow deposition of a liquid biological specimen therethrough, a separation membrane secured to the cap and extending across the aperture, a cap ring rotatably secured about the collection housing, and a tether coupling the cap to the cap ring.