Separation device for separating a filtrate from a sample fluid, comprising: a sample container for receiving the sample fluid, a filter plunger to be introduced into the sample container, which filter plunger has a filter element at its front end and an interior to receive the filtrate obtained, wherein an annular chamber is formed between an inner wall of the sample container and an outer wall of the filter plunger after insertion of the filter plunger into the sample container, which annular chamber is sealed against the exterior by a sealing element and in which an air cushion, acting on the sample fluid, is formed upon introduction of the filter plunger into the sample container, wherein the annular chamber is flow-connected with the front side of the filter element after a sample-side rim of the filter plunger is in contact with the bottom of the sample container and thus insertion of the filter plunger is terminated, characterised in that the filter plunger has a grip element on the opposite end and a grip sided recess of the filter plunger contains a filtrate collector vessel, which tapers towards the filter element, having a tip which contacts the filter element, wherein the filtrate collector vessel is attached to the grip element of the filter plunger and the grip element together with the filtrate collector vessel can be unscrewed from or wrenched off the filter plunger, wherein the sample-side rim extends beyond the front face of filter element and forms a frontal wetting chamber in which are provided recesses in the rim or flow openings which establish flow connection between the annular chamber and the frontal wetting chamber, and/or the bottom of the sample container has notches or groove-shaped recesses for establishing flow connection between the annular chamber and the front side of the filter element, after the sample-side rim is in contact with the bottom of the sample container. a sample container for receiving the sample fluid, a filter plunger to be introduced into the sample container, which filter plunger has a filter element at its front end and an interior to receive the filtrate obtained, wherein an annular chamber is formed between an inner wall of the sample container and an outer wall of the filter plunger after insertion of the filter plunger into the sample container, which annular chamber is sealed against the exterior by a sealing element and in which an air cushion, acting on the sample fluid, is formed upon introduction of the filter plunger into the sample container, wherein the annular chamber is flow-connected with the front side of the filter element after a sample-side rim of the filter plunger is in contact with the bottom of the sample container and thus insertion of the filter plunger is terminated, characterised in that the filter plunger has a grip element on the opposite end and a grip sided recess of the filter plunger contains a filtrate collector vessel, which tapers towards the filter element, having a tip which contacts the filter element, wherein the filtrate collector vessel is attached to the grip element of the filter plunger and the grip element together with the filtrate collector vessel can be unscrewed from or wrenched off the filter plunger, wherein the sample-side rim extends beyond the front face of filter element and forms a frontal wetting chamber in which are provided recesses in the rim or flow openings which establish flow connection between the annular chamber and the frontal wetting chamber, and/or the bottom of the sample container has notches or groove-shaped recesses for establishing flow connection between the annular chamber and the front side of the filter element, after the sample-side rim is in contact with the bottom of the sample container.