Inlet sinkers—also known as inlet filters or sparging stones—are stainless‑steel components used at the end of solvent pickup lines in HPLC and LCMS systems.

Their purpose is to provide clean solvent delivery and stable instrument operation by filtering particulates and ensuring the solvent line remains fully submerged during use.

What an Inlet Sinker Does

Primary Functions

• Acts as a weighted anchor

  • The stainless‑steel construction provides enough weight for the sinker to stay at the bottom of the solvent reservoir, keeping the solvent inlet tubing submerged at all times.

• Serves as a particle filter

  • Many inlet sinkers are designed as sparging stones or porous stainless‑steel filters, which prevent particulate contamination from entering the tubing and pump.

• Supports consistent solvent uptake

  • By keeping the tubing fully submerged, inlet sinkers reduce the risk of introducing air bubbles that may cause pump cavitation, unstable baselines, and flow irregularities.

Why the Term “Sinker” Is Used

Naming Origin

• The term inlet sinker comes from the sinker’s ability to sink naturally to the lowest point of the mobile‑phase bottle, thanks to its stainless‑steel mass.

Interchangeable Names

• Also referred to as:

  • Stainless‑steel inlet filter
  • Sparging stone
  • Inlet stone
  • Mobile‑phase pickup filter

When Inlet Sinkers Are Used

Common Applications

• HPLC solvent reservoirs
• LC‑MS mobile‑phase bottles
• Degassed or sparged solvents
• Buffered aqueous mobile phases
• High‑purity solvent systems where particulate control is essential

Typical Benefits

• Reduced pump seal wear
• Lower risk of system blockages
• Improved retention‑time stability
• Cleaner baseline performance

Available Products

MICROSOLV supplies stainless‑steel sparging stones and inlet sinkers designed for various tubing sizes and filtration needs.  Click HERE for mobile phase sparging stones (inlet sinkers).