HP 5890 Series II Plus Reference Manual page 15

Columns and Fittings
Fittings
Graphite O•ringsor ferrules have excellent sealing quality and long
service life, can be used continuously to 400 C, and are generally
recommended for most applications, particularly capillary and glass
columns. They are also recommended for inlet and detector liners, and
for split/splitless capillary inlet inserts.
Since they do not adhere permanently to glass or metal, they can be
removed easily without damage to the column, tubing, liner, or insert.
A rear metal ferrule may be needed if recommended by the
manufacturer.
Commonly used with metal columns and tubing, brass nuts and
ferrules on the column prevent damage to inlet and detector liners,
but may develop leaks above 250 C or with temperature
programming.
Also commonly used with metal columns and tubing, stainless steel
fittings minimize possibility of leakage at high temperature, but
require care in installing columns; overtightening may damage the
column end or inlet/detector fitting.
Teflon ferrules may be used to 250 C but are recommended only for
isothermal work, because they develop leaks when
temperature•programmed.
Commonly used with glass columns, Vespel (or graphite•filledVespel)
ferrules are reusable and work well to 350 C. These ferrules may
leak or crack if tightened when cold.
Glass columns can be installed using silicone O•rings. For O•ring
installation, a back metal ferrule, reversed, is necessary to provide a
flat surface to seal against.
Silicone O•ringsare useful to about 250 C, but, due to bleed, interfere
in high•sensitivitywork. They also gradually lose elasticity and crack,
so they must be replaced fairly often.
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