One-piece ferrules are available in two designs: the standard 1/16-inch compression-type and the short, compact design. Agilent GCs typically use the compact design at the injector and detector, but we always recommend using the 1/16-inch compression-type ferrule at the detector if you are doing GC/MS analysis. Whichever configuration you select it is essential that you use the corresponding standard or compact nut.
In addition, ferrules generally are available in three compositions: graphite, Vespel®, and Vespel®/graphite. Composition usually is a matter of preference, but we recommend Vespel®/graphite ferrules for GC/MS because they seal with minimum torque, maintain sealing performance under high pressure and vacuum, and are reusable.
The ferrule should always have a slightly larger ID than the column OD, so that it can compress and seal around the column. For example, a 0.45mm ID Restek column, which has an OD of approximately 0.7mm, would require a ferrule with an ID of 0.8mm.
