A mechanical separator (40, 40B, 40C, 40D, 140, 140A, 240, 240A, 340, 440, 540) for separating a fluid into first and second phases within a collection container, comprising: a separator body (41, 41C, 41D, 141, 141A, 241, 241A) comprising: a float (42, 42B, 42C, 42D, 142, 142A, 242, 242A, 342, 442, 542), having a first density; and a ballast (44, 44B, 44C, 44D, 144, 144A, 244, 244A, 344, 444, 544), having a second density greater than the first density, wherein a portion of the float (42, 42B, 42C, 42D, 142, 142A, 242, 242A, 342, 442, 542) is connected to a portion of the ballast (44, 44B, 44C, 44D, 144, 144A, 244, 244A, 344, 444, 544), and wherein at least a portion of the separator body (41, 41B, 41C, 41D, 141, 141A, 241, 241A) is adapted for deformation upon applied rotational force characterized in that the separator body (41, 41C, 41D, 141, 141A, 241, 241A) has a through-hole (46, 46C, 46D, 146, 146A, 246, 246A, 346, 446, 546) defined therethrough, the through-hole (46, 42B, 46C, 46D, 146, 146A, 246, 246A, 346, 446, 546) comprising a first opening (48, 248, 56C, 549) and a second opening (80, 250, 60C, 551) and adapted to allow fluid to pass through the separator body (41, 41C, 41D, 141, 141A, 241, 241A), and upon application of a rotational force to the collection container containing the separator (40, 40B, 40C, 40D, 140, 140A, 240, 240A, 340, 440, 540), the separator (40, 40B, 40C, 40D, 140, 140A, 240, 240A, 340, 440, 540) is adapted to rotate from a first initial position in which the through-hole (46, 42B, 46C, 46D, 146, 146A, 246, 246A, 346, 446, 546) is oriented in an open position for allowing fluid to pass through the through-hole (46, 42B, 46C, 46D, 146, 146A, 246, 246A, 346, 446, 546) and into the collection container to a second sealing position in which the separator body provides a seal with an inner surface of the collection container preventing fluid from being received through the through-hole (46, 42B, 46C, 46D, 146, 146A, 246, 246A, 346, 446, 546) and around the separator (40, 40B, 40C, 40D, 140, 140A, 240, 240A, 340, 440, 540). a separator body (41, 41C, 41D, 141, 141A, 241, 241A) comprising: a float (42, 42B, 42C, 42D, 142, 142A, 242, 242A, 342, 442, 542), having a first density; and a ballast (44, 44B, 44C, 44D, 144, 144A, 244, 244A, 344, 444, 544), having a second density greater than the first density, wherein a portion of the float (42, 42B, 42C, 42D, 142, 142A, 242, 242A, 342, 442, 542) is connected to a portion of the ballast (44, 44B, 44C, 44D, 144, 144A, 244, 244A, 344, 444, 544), and a float (42, 42B, 42C, 42D, 142, 142A, 242, 242A, 342, 442, 542), having a first density; and a ballast (44, 44B, 44C, 44D, 144, 144A, 244, 244A, 344, 444, 544), having a second density greater than the first density, wherein a portion of the float (42, 42B, 42C, 42D, 142, 142A, 242, 242A, 342, 442, 542) is connected to a portion of the ballast (44, 44B, 44C, 44D, 144, 144A, 244, 244A, 344, 444, 544), and wherein at least a portion of the separator body (41, 41B, 41C, 41D, 141, 141A, 241, 241A) is adapted for deformation upon applied rotational force characterized in that the separator body (41, 41C, 41D, 141, 141A, 241, 241A) has a through-hole (46, 46C, 46D, 146, 146A, 246, 246A, 346, 446, 546) defined therethrough, the through-hole (46, 42B, 46C, 46D, 146, 146A, 246, 246A, 346, 446, 546) comprising a first opening (48, 248, 56C, 549) and a second opening (80, 250, 60C, 551) and adapted to allow fluid to pass through the separator body (41, 41C, 41D, 141, 141A, 241, 241A), and upon application of a rotational force to the collection container containing the separator (40, 40B, 40C, 40D, 140, 140A, 240, 240A, 340, 440, 540), the separator (40, 40B, 40C, 40D, 140, 140A, 240, 240A, 340, 440, 540) is adapted to rotate from a first initial position in which the through-hole (46, 42B, 46C, 46D, 146, 146A, 246, 246A, 346, 446, 546) is oriented in an open position for allowing fluid to pass through the through-hole (46, 42B, 46C, 46D, 146, 146A, 246, 246A, 346, 446, 546) and into the collection container to a second sealing position in which the separator body provides a seal with an inner surface of the collection container preventing fluid from being received through the through-hole (46, 42B, 46C, 46D, 146, 146A, 246, 246A, 346, 446, 546) and around the separator (40, 40B, 40C, 40D, 140, 140A, 240, 240A, 340, 440, 540).