PTFE-faced septa are suitable to overcome the degradation due to prolonged high temperatures which occurs in silicone rubber septa. The degradation results in baseline drift and additional peaks. It is generally fixed with the PTFE faced towards the column packing.
Application: Glass vials equipped with stir bars may be sealed with PTFE faced silicone septa for solvent drop microextraction analysis of water samples. This may be used in sealing the vials used for headspace solid-phase microextraction (HS-SPME) procedure during determination of aldehydes in drinking water.