SilTite ferrules are a unique metal ferrule specifically designed for connecting fused silica GC columns and tubing to mass spectrometer interfaces and injectors. Once fitted, SilTite ferrules provide a continuous leak free connection without the need to re-tighten the nut after a few temperature cycles. SilTite ferrules make Graphite/Vespel® ferrules obsolete for use in GC-MS connections. Their performance and cost effectiveness also makes them ideal for connecting GC columns to injectors and atmospheric detectors.
Figure 1. MS trace using a graphite Vespel ferrule after 5 temperature cycles.
Figure 2. MS trace using a SilTite ferrule after 5 temperature cycles. (Using an MS, no leaks can be detected, even after 400 temperature cycles between 70ºC and 400ºC).
SGE has developed a metal ferrule specifically for use with fused silica GC columns. Combining a specially designed ferrule and nut system, the SilTite ferrules must be used in conjunction with this special nut that is supplied with the ferrules. The geometry of the nut and ferrule combination makes it possible to swage the end of the ferrule to the fused silica tubing. This creates a leak-free seal (Figure 3) that never needs re-tightening - even after 400 temperature cycles between 70°C and 400°C. Constructed from identical material, the ferrule and nut expand and contract at the same rate as the oven temperature heats up and cools down. In contrast, the Graphite/Vespel ferrules have a different rate of expansion to that of the metal nut. As the oven temperature changes, leaks may occur if the metal nut is not retightened. This allows air and water to enter into the MS, causing damage to the MS and a reduction in the quality of your analysis.
For easy installation gradually tighten the nut until the ferrule just begins to hold the fused silica. Then tighten a further 60°; a leak tight seal is guaranteed. When using Siltite ferrules with stainless steel tubing, the ferrule should be tightened greater than 60° (between 90 - 180°) to ensure a leak free seal.