On Tue, 11 Oct 2005 17:12:40 +0100, Doctor Drivel
wrote:

Paste works its way into any imperfections where the fitting meets the
olive.

And causes all sorts of heartache to people who look after Gas
Chromatography/Mass Spectrometry kit. PTFE tape also often carries
silicones (why exactly this is needed on a non-stick material defeats me)
which also give ghost peaks. It is entirely possible to achieve a good
seal with compression fittings with no adjuncts. Even the best seals leak
to an extent. If you can beat the detection range of a sniffer detector it
is as good as it gets. The mass Spectrometer will still pick up air gases
N/O/H2O on a really well sealed system. The molecules actually migrate
against the flow. The septum is normally the major culprit. Do feel free
to come back when you have som understanding.

Jonh Schmitt

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