Overview

When solvents exit the vacuum degasser, it is essential that they remain free of dissolved gases before entering the HPLC pump. PEEK tubing provides an excellent barrier against atmospheric gas permeation, helping maintain low oxygen levels in the mobile phase. PTFE, however, is a permeable material and readily allows oxygen to diffuse back into the solvent once it returns to ambient pressure.

For this reason, PTFE is unsuitable for tubing placed after the degasser, while PEEK offers superior solvent integrity and pump stability.

🔹 Why This Is Important

Using the wrong tubing material after the degasser can compromise analytical performance. Re‑gassed mobile phases can cause:

• Pump cavitation
• Flow rate instability
• Noisy or drifting baselines
• Shifts in retention times
• Poor peak reproducibility

Ensuring that degassed solvents remain oxygen‑free is a critical step in maintaining precise and reliable HPLC results.

When solvents enter the HPLC pump, they should remain fully degassed to ensure consistent flow delivery and stable chromatographic performance. PEEK tubing is the preferred material for maintaining this degassing integrity because it does not allow atmospheric gases to permeate back into the mobile phase.

PTFE, by contrast, is highly permeable and easily allows oxygen to diffuse back into the solvent after it exits the degasser. Although PTFE works effectively inside the degasser—where its permeability helps remove gases under vacuum—this same property makes it unsuitable for tubing used after the degasser. Once exposed to ambient pressure, PTFE can quickly re‑introduce dissolved gases into the mobile phase, undermining the purpose of degassing.

For best results and maximum system stability, PEEK tubing should always be used after the degasser, while PTFE should be reserved for locations where its permeability is advantageous.