What a PTFE membrane actually does
I have watched a postdoc ruin a 40-sample pesticide panel by pulling the wrong filter out of the drawer. The membrane was a 0.45 µm nylon disc, fine for aqueous buffers, but the samples were in 90:10 hexane:acetone. The nylon swelled, shed a little polymer, and every chromatogram came back with a baseline drift and three ghost peaks that nobody could identify until we ran a blank. That afternoon cost us a week. The fix was a PTFE membrane filter, 13 mm, 0.2 µm, hydrophobic, in a polypropyle...
