Four polymers, four failure modes, and no universal winner
A 12-hour sequence on a GC kept throwing a ghost peak at 11.2 minutes, RSD on the internal standard climbing from 1.8% to 6.4%. The column was fine, the inlet liner was new, the standards were fresh. The culprit was a silicone septum that had been fine for hexane extracts but was sitting in a tray of dichloromethane. The silicone had swollen 22% by volume, the puncture channel no longer re-sealed, and solvent vapour was bleeding into the carrier stream between injections. Changing to a...
