Agilent Technologies 6850 Series II User Information page 175

4.
5.
6.
The Teflon ferrule may lose its seal in time. If so, first retighten the retaining
nut and, if the seal still leaks, install a new Teflon ferrule and needle.
When not in use, loosen the retaining nut to avoid premature leaks.
If you are cutting replacement needles directly from fused silica column
material:
1.
2.
3.
Changing septa
If the septum leaks, you will see symptoms such as longer or shifting retention
times, loss of response, and/or loss of column head pressure. Additionally, the
detector signal will become increasingly noisy.
The useful lifetime of septa is determined by injection frequency and needle
quality; burrs, sharp edges, rough surfaces, or a blunt end on the needle
decrease septum lifetime. When the instrument is used regularly, daily septum
replacement is recommended.
The type of septa you use will depend on your chromatography needs. You can
order septa directly from Agilent Technologies; see the Agilent catalog for
consumables and supplies for ordering information.
Caution The procedure for changing septa differs depending on whether you cool
on-column inlet has a cooling tower assembly or a septum nut. Make sure to
follow the correct procedure for your inlet!
Released: March 2004
Loosen the retaining nut just enough so the needle is again free. Depress
the syringe plunger slowly until it pushes the needle to the end of the
barrel, then tighten the retaining nut to firm finger tightness.
Use a solvent to rinse the syringe and check for leaks or blocks.
Leaks (inability to eliminate air bubbles) may be fixed by further tight-
ening the retaining nut. Blocks (or serious leaks) require repeating this
procedure.
Column material for making needles must have an outside diameter
smaller than both the inside diameter of the on-column inlet (0.23 mm)
and the inside diameter of the installed column.
Column material must be washed free of active stationary phase.
Score the column material about 1/4-inch from its end. Break off the end
and discard. Then measure, score, and break off a 115+5 mm length to use
as the syringe needle.
6850 Series II GC User Information
Routine Maintenance: Inlets
Maintaining a cool on-column inlet
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