Vacuum filtration: bottle-top vs. standalone setups

A vacuum filtration setup connects a filter funnel and membrane to a vacuum source—a pump or house vacuum line—so that a pressure difference, not gravity, drives the liquid through the membrane. That makes it well suited to volumes and viscosities where a syringe push would be impractical.

Bottle-top filters

A bottle-top filter combines the funnel and membrane in a single disposable unit that screws directly onto a receiver bottle. The whole assembly is typically sold pre-sterilized, which makes it a common choice for sterile filtration of media, buffers, and other solutions where avoiding a separate autoclave cycle matters. Because the funnel and membrane are a single unit, there's nothing to disassemble or clean between uses—the trade-off is a fixed pore size and material per unit, and a per-use cost that a standalone system doesn't carry.

Standalone funnel systems

A standalone system pairs a reusable glass or plastic funnel with a separate membrane and typically a support base and flask. This format is common where you need flexibility to swap pore size or material between runs, or where per-use cost matters more than convenience at higher volumes. It does require cleaning (and for sterile work, sterilizing) the funnel and base between uses—worth weighing against a bottle-top's disposability if turnaround time is tight.

What actually drives throughput

Filtration area and vacuum level matter more than the pore rating alone—a larger-diameter membrane clears a given volume faster at the same pore size, and adequate vacuum keeps flow from stalling as the membrane loads with particulate. A sample that's slow to filter is more often a sign to increase area (a larger funnel/membrane) or pre-filter first, rather than simply loosening the pore rating and risking under-retention.

Matching membrane to the funnel

Membrane material selection follows the same logic as any other format—hydrophilic materials like PES or nylon for aqueous samples, PTFE for aggressive solvents. See our membrane material guide for the full comparison. Diameter needs to match the funnel exactly; an undersized membrane won't seal properly and can let sample bypass the filter entirely.