The Filter Mate Filtration System provides a convenient and inexpensive method of filtration requiring no transfer steps. The Filter Mate fits directly into the digestion vessel and is pushed through the liquid being filtered to the bottom of the cup with a detachable plunger. After filtration is complete, the plunger is removed and discarded while the filter assembly remains in the bottom of the cup. This arrangement does not interfere with storage or use of the vessel in an auto sampler.