Crimp seal with PTFE/butyl septum (Pharma-Fix) may be used to seal standard residual solvents for the determination of residual solvents in drug substances using headspace gas-chromatography coupled with flame ionization detector (HS-GC-FID).

PTFE-faced butyl septum was used in sealing headspace vials to analyse the sampling efficiency and breakthrough of methyl bromide on activated charcoal using GC. It was also used for sealing water samples during headspace analysis with GC-FID, in a study which demonstrates cross-validation of methods used for methyl-tert-butyl ether (MTBE) analysis.