Methods, kits and devices for separating phospholipids and proteins from small molecules in biochemical samples can feature an apparatus having a wetting barrier, at least one fit and a separation media. For example, an apparatus can include at least one wall defining a chamber having an exit and an entrance; a wetting barrier disposed between the exit and entrance, so as to define a separation media space located between the wetting barrier and the exit and a sample receiving area located between the wetting barrier and the entrance; and a separation media disposed adjacent to the wetting barrier and having a specific affinity for phospholipids. The wetting barrier is adapted to (i) retain the liquid sample and a protein precipitating agent in the sample receiving area under a first force, thereby facilitating the formation of a protein precipitate and a processed sample, and (ii) flow the processed sample through the wetting barrier and separation media under a second force, wherein the second force is greater than the first force, thereby retaining the protein precipitate in the sample receiving area, retaining phospholipids in the separation media, and eluting small molecules.