Abstract: A plate assembly for performing multiple filtrations with the use of a vacuum offers advantages for small samples due to the construction of its component plates, which include an upper plate with apertures forming sample wells, a membrane sheet forming the floor of each well, a collection plate with individual wells underneath the membrane sheet, aligned with the upper plate apertures, and a drop guide plate between the membrane sheet and the collection plate to guide and force small quantities of liquid downward from the membrane into the collection wells. The arrangement permits extremely small quantities of species on the membrane to be drawn into the collection wells without dilution, and avoids cross contamination between collection wells.