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Diffusion Pump Fluid
If the diffusion pump fluid is allowed to operate with no column (carrier gas) flow into the
vacuum system, vapor from the diffusion pump fluid can drift up into the vacuum
manifold. A more serious problem is when fluid is back streamed into the vacuum
manifold by sudden or improper venting of the vacuum system. If a diffusion pump has
back streamed, a prominent peak will often be seen at m/z 446 and the spectral baseline
will exhibit increased background noise.
Remedy
If m/z 446 appears, please call Agilent for assistance.
Foreline Pump Oil
Foreline pump oil contamination is characterized by peaks spaced 14 amu apart
(hydrocarbons). Contamination with foreline pump oil is less common than contamination
with diffusion pump fluid.
Remedy
Call Agilent for assistance.
A crude sign of a "leak-free" MS
system is when the ion ratio
of m/z 28 (nitrogen) over m/z 32
(oxygen) is approximately two
or greater.
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