A filtration assembly for separating solids from liquids contained in a sample, and a method for preparing such a sample are disclosed herein. According to one embodiment, the filtration assembly includes an inner element (100) with proximal and distal ends (102,103) and a sample (200) disposed therein. A reinforcing sleeve (300) is disposed around the inner element (100) to form a sample receiver (250) with proximal and distal ends (252,253). A filter (400) is disposed at the open proximal end of the sample receiver (252) and a filtrate receiver (500) is placed over the filter (400) and threadedly engaged with the sample receiver (250) to clamp the filter (400) therebetween. Then, the receivers (250,500) are inverted and a pressure is applied to the sample (200) to force a liquid component (200a) through the filter (400) into the filtrate receiver (500), while solids (200b) are retained in the sample receiver (250).