Graphite/Vespel Ferrule (GC) — Sales and Instrument Support

High-temperature graphite/Vespel ferrule for gas chromatography, used at the inlet and detector column connections. The blend is a polyimide matrix filled with graphite; the usual 60/40 grade combines the sealing softness of graphite with the mechanical stability of polyimide, and is normally used up to roughly 350 C.

Ferrule internal diameter has to match the column outside diameter - 0.25, 0.32 and 0.53 mm columns take different ferrules - and a ferrule is a single-use sealing part once it has been compressed.

The one habit that prevents most leaks

Polyimide relaxes on its first heat cycles, so a connection that was leak-tight when cold works loose after the oven has been to temperature. Re-tighten by a small amount after the first one or two cycles, then leak-check again.

A leaking column connection lets air and water into the carrier gas, and the consequences arrive later: accelerated column bleed, retention times shifting, a rising baseline at high oven temperatures, and oxidised stationary phase that no amount of conditioning recovers. Pure graphite ferrules go to higher temperatures but are softer and can shed particles into the inlet.