A Homemade Vacuum Filtration System for Filtering Into Sample Vials

Most vacuum filtration systems only allow you to collect the filtered liquid in a large (typically 1L) erlenmyer flask or glass basin. We wanted a system that would let us easily filter into a disposable glass sample vial, such as the 40mL and 60mL EPA VOA vials. A commercially available pyrex filter dome (shown above, purchased from Kimble) lets you do this, but it is designed to be placed on a piece of flat glass and the bottom rim coated with vacuum grease. We found that without the vacuum grease, a good seal was virtually impossible. Thus we fabricated the Delrin base shown above. It has a groove to contain a PTFE-encapsulated silicone o-ring (available from McMaster) that seals well against the filter dome with no vacuum grease. The cylinder in the center holds a 40mL VOA vial steady and raises it to just below the bottom of the filter stem. The center cylinder is removeable, and reveals a second hole for 60mL VOA vials. The stopper at the top is green rubber. It works OK until you spill solvent on it, and then you have to go get another stopper. We're looking for viton stoppers, but haven't found any yet. We use this system for filtering solvents through 42mm GFF filters, and for speeding up column chromatograpy separations using either solid-phase extraction (SPE) cartridges or pipettes packed with silica gel.