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Ferrule for GC
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Choosing the Right Ferrule
Although graphite and Vespel /graphite ferrules each have advantages and disadantages, the choice of ferrule composition is largely a personal preference.
Graphite ferrules are soft, easy to seal, stable to 450°C, and contain no binders that might off-gas.
Vespelgraphite ferrules work better for vacuum and high-pressure applications (e.g., GC/MS) because they will not fragment or allow oxygen to permeate into the system, whereas graphite ferrules will.
Because Vespe®/graphite ferrules are made from a harder material, they might require retightening after several temperature cycles.
Alumaseal ferrules are ideal for GC/MS. They will not crack or fragment and require no retightening after temperature cycles.
100% Graphite Ferrules •
• Provides a stable seal
•
• Porous to O2 (not for GC- MS).
• Temperature Limit 450°C.
• Forms ‘soft’ grip with column.
• Re-useable
15% Graphite / 85% Vespel® Ferrules •
• Hard material, long lifetime.
• Temperature limit 350°C.
• Must re-tighten after initial temperature cycles
•
Forms strong grip with column.•
Cannot be re-used with another capillary column•
For GC-MS interfaceSilTite
• SilTite ferrules form a strong, permanent,.
airtight seal around the capillary column
•
The metal SilTite ferrule and nut are.made from the same material and
therefore have the same thermal
expansion coefficient. As the oven heats
up and cools down, the nut and ferrule
expands and contracts at the same rate,
eliminating annoying leaks and the need
to re-tighten the ferrule after installation.
•
The base of the SilTite ferrule is flat and.forms a perfect seal with the MS
interface, covering the whole transfer
interface.
•
Specifically designed non-Swagelock.SilTite nuts are characterized by two
notches on the outer surface of the nut.
The inner taper of the nut corresponds to
the angle of the SilTite ferrule, ensuring
an even closure of the ferrule around the
whole column, eliminating leaks.
•
SilTite metal ferrules have a temperature.tolerance well above the limit of the
injector, MS interface or GC oven.
•
SilTite nuts and ferrules are available for.most major GC/MS instrument interfaces
Ferrule choices Material Type Suitable for GC-MS Temperature Limit (°C) Can be re-used Graphite No 450 Yes Graphite / Vespel Yes 350 No Stainless steel (SilTite™) Yes 500 No
https://blog.sciencenet.cn/blog-258674-696644.html
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