Dear listmembers

We perform analysis in a Delta S mass spect. Since
some days ago, we detected, besides humidity, a
nitrogen signal (mass 28) in cup 2 after sequence
finishes in both standard and sample sides.  We
thought it could be air presence. Perform some test,
we found out that there are the same signal when we
fill the bellows with reference gas. If we remove
reference gas and fill again twice or three times,
mass 28 signal comes considerably down, but if
sequence is done, mass 28 appears again.

A leak along the capillaries and tubes seems don't to
be the problem, because we check them. Also, the
problem occurs with both CO2 and Hydrogen gases. We
believe the problem could be in a common point, since
we fill the gas also from the refill gas reservoir by
the 22 and 24 valves and perform a test injecting
Argon directly to the inlet system with the same
results.

Could the problem be at the change over valves? Or
nitrogen signal belongs to the gases as contamination?

We will appreciate your help and comments!

Regards




=====
Wilmer Guevara
Stable Isotope Laboratory
CEL/Division de Generacion Geotermica
Km 11 1/2 Carretera al Puerto de La Libertad
El Salvador, C.A.
e-mail: [log in to unmask]
Phone:(503)228-1400   Fax: (503)228-0781
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