Iso9001 luer lock PTFE membrane filter on stock Trace2 PTFE Membrane, 25mm, 0.22μm (F2300-19) Trace2 PTFE Membrane Syringe Filter, 25mm, 0.22μm, 100-pk Adding a syringe filtration step prior to injection not only helps to ensure more consistent and reliable results; it also helps protect delicate instruments and prolongs column life.