Patent ID: 6884341

Claim:
An apparatus for capturing a desired quantity of material from a sample suspension on a filter, comprising: a body member defining a chamber and having opposed ends, an outlet port in one of said ends, and an inlet port; said inlet port and said outlet port defining a single pathway for sample suspension to flow though said apparatus; a substantially planar filter mounted within said chamber between said inlet port and said outlet port and completely across said single pathway, so that sample suspension flowing through said apparatus must flow from said inlet port through said filter and to said outlet port; said filter being deformable toward said outlet end at a predetermined pressure change across said filter and having a first porous portion and a second porous portion concentrically arranged centrally of said first portion, said second portion constructed to be more restrictive to flow than said first portion, said predetermined pressure change selected so that when a desired quantity of material has been captured by said first portion, said substantially planar filter deforms against said outlet end such that all flow of sample suspension through said apparatus must flow through said more restrictive second portion; and means for providing a pressure to cause said sample suspension to flow through said apparatus.