- Hewlett-Packard Reference Manual

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/splitlesscapillary 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.