Solvent Bottle Cap Assembly, 1L — Sales and Instrument Support

Solvent reservoir cap assembly for a 1 litre bottle, with ports for the solvent inlet line and a vent so air can replace the solvent as the pump draws it. The inlet line ends in a weighted sinker frit that keeps the pick-up point below the liquid surface.

The cap does two jobs that are easy to overlook. It keeps airborne dust and lab humidity out of the mobile phase, and it holds the inlet line at a fixed depth so the pump never draws air near the end of a bottle.

What fails, and how it shows up

• A cracked or loose port lets air into the inlet line: the pump shows pressure ripple and cavitation although the bottle is full.
• A blocked sinker frit starves the pump, giving falling flow and a noisy baseline.
• A vent left sealed pulls a partial vacuum in the bottle and the flow slowly drops.

Aqueous buffers should not be left standing in a capped reservoir between runs; microbial growth in the bottle ends up in the frit and then in the column.