Whatman PTFE (type WTP) membranes are chemically stable and inert. They are suitable for applications involving aggressive organic solvents, strong acids, and alkalis. PTFE membranes are particularly suitable for preparing samples for HPLC analysis. The hydrophobic nature of the membrane also has applications for air and gas sterilization. The membrane is laminated onto a non-woven polypropylene support web for improved strength and handling and can be used at temperatures up to 150°C.