Membrane selection for HPLC and GC sample prep

Why you filter immediately before injection

Particulate in an injected sample can clog the column frit, damage the column bed over repeated injections, and cause irregular back-pressure. A quick syringe-filter step immediately before injection is cheap insurance against all three, and it's standard practice across most HPLC and GC methods.

Match the membrane to your mobile phase

The membrane needs to be chemically compatible with your sample solvent, not just your final mobile phase—PTFE for aggressive or non-aqueous solvents, PES or nylon for aqueous methods, with the usual caveat that nylon can adsorb some polar and basic compounds worth checking against your specific analyte. See our membrane material guide for the full comparison.

Extractables: the HPLC-specific concern

Beyond basic compatibility, HPLC and especially LC-MS work is sensitive to extractables—trace compounds the membrane itself can shed into the sample, which can show up as unexpected peaks or ion-suppression noise in the result. Low-extractable or "HPLC-certified" filter lines exist specifically to address this; for trace-level or MS-detected methods, this is worth checking rather than assuming any generic filter is equivalent.

Don't lose your analyte to the filter

Some membranes bind certain compounds—proteins to some materials, basic drugs to unmodified nylon, and so on. For trace-level analytical work, this can mean losing meaningful analyte to the filter surface, especially with low sample volumes where the filter's surface area is large relative to the total analyte mass. If low recovery is a concern, low-binding membrane options and running a recovery check with your actual analyte are both worth doing before you standardize a method.

Diameter and format for small volumes

HPLC/GC sample prep typically uses small syringe-filter formats (4mm–13mm) suited to the small injection volumes involved—there's rarely a reason to use a larger-format filter for this step, since it just wastes sample to the filter's dead volume without any benefit.