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Technical Description: System
Introduction of a Gas Sample
B-14
Prima PRO & Sentinel PRO Mass Spectrometers User Guide
Figure B–10. Typical arrangement of RMS inlet system
The Sentinel PRO introduces the gas sample directly from
atmospheric pressure via a membrane inlet. The dimethylsilicone
membrane is fitted to the end of an inlet probe, which replaces the
leak element in the Prima PRO assembly. The end of this stainless
steel inlet probe locates onto the ion source and is insulated by a
ceramic end piece.
The selected sample gas flows from the stream selector, RMS, to the
inlet probe and membrane, and then returns to the stream selector to
be exhausted. This loop operates at a reduced pressure, typically
approximately 0.8 bar(a), generated by a large capacity circulator
pump attached to the RMS valve to draw sample to the instrument.
The membrane inlet is used as this provides preferential transmission
of organic compounds compared with the principle air constituents.
The concentration of organic compounds entering the ion source is
increased by a factor of between 10 and 100, which gives
significantly improved detection limits for these components,
compared with a standard capillary inlet.
Transfer
line
To bypass line
and vacuum
pump
Thermo Fisher Scientific
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