Replace ferrule?
Posted: Thu Jul 10, 2008 8:00 pm
by tilly
Is it necessary to replace the ferrule each time a capillary column is fitted to FID? When the column inlet/outlet unscrewed and column removed is it best to insert the column ends into rubber septa to stop air getting in the column. These perhaps seem silly questions
but hope someone can help and say what is best.
Many thanks
Posted: Thu Jul 10, 2008 8:59 pm
by Consumer Products Guy
We usually leave the nut and ferrules in place when we remove a column from the GC, the graphite and vespel-type ferrules are reusable. For air-sensitive phases like PEG, we will stick the column ends into an old septum. Before re-installation, we will cut a few mm off the end of the column so any septum cored would not plug the column or get into the GC (the ferrules are moveable). If we replace the ferrule or it comes off, we also cut off a few mm then.
Posted: Sat Jul 12, 2008 2:19 am
by Bruce Hamilton
There are a range of different ferrule materials, mainly defined by detector, as MS have special reuirements - SGE catalog offers quite a combination of choices. The answer depends on the type you have.
The Vespel ferrules are very hard, easily reusable, but have much lower thermal limits. the 85:15 Vespel/graphite is softer, should be retighted after a few uses, can be reused ( despite what SGE say ) and has slightly higher temperature limit. Graphite ferrule have high temperature resistance, are very soft, and may be reused - depending on how tight they were installed. there are also now metal ferrules especially for MS, refer SGE Siltite.
Most people leave the nut and ferrules on their column, and some put septa over column ends. I don't bother with the septa on columns for stoarge, as you should fully purge all air from the inlet and column before starting to warm the instrument.
Bruce Hamilton