INFICON HAPSITE Smart Plus Chemical Identification System - Manual (Page 506)

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HAPSITE Smart Plus Operating Manual
16.5.1 Contamination of the Mass Spectrometer
Contamination of the Mass Spectrometer manifold can occur every time an internal
component is changed, or vacuum is broken. This can consist of water and/or light
hydrocarbons. These will be seen in the mass spectrum even when the isolation
valve is closed. (The source of contamination is not coming from the GC module.)
16.5.1.1 Symptoms
Symptoms of contamination are a high background of water or hydrocarbons in the
mass spectrum, a high baseline in the TIC plot, or a higher than normal base
pressure. Contaminants on the Ion Source or the NEG Pump will be driven off as
these components are heated. Use this heat to decontaminate the instrument.
16.5.1.2 Decontamination
Decontaminate the vacuum manifold using the Service Module. Pump for a few
hours for water or light hydrocarbons contamination, or as long as 24 hours if the
contamination is heavy. Remember that various components of the vacuum
manifold will get hot and aid in driving off unwanted substances. Turn the Ion
Source filament ON and heat the NEG Pump to 400

C when decontaminating a
system. If the contamination will not go away after a full day of pumping, the
suspect component must be removed and replaced. Remember, care must be
taken when handling internal components of the vacuum system. Always use new
gloves or a clean lint free cloth to avoid contact with skin oils.
16.5.2 Contamination of the Gas Chromatograph
Contamination of the Gas Chromatograph (GC) can occur if hot heavy organic
gases are sampled, and then condense in the system. These will be seen in the
mass spectrum only when the isolation valve is opened. (Background may be high
after the isolation valve is first closed, but will drop off after a few minutes.)
16.5.2.1 Symptoms
Symptoms of contamination are a high background of hydrocarbons in the mass
spectrum, or a high baseline in the TIC plot.
16.5.2.2 Decontamination
Decontaminate the GC by moving the HAPSITE to an area where the air is
relatively clean or connect the transfer line to a canister of a pure gas (N
2
or Air).
Flush the sampling pathway by setting up a GC method to Loopfill for 5 minutes.
Repeat this method until the source of the contamination is flushed out. Heating all
temperature zones to the maximum allowable setting will aid in the cleansing of the
GC. Some compounds may become trapped at unheated locations and might
require a longer time period to be flushed out. If the boiling point of the contaminate
is greater than the maximum temperature of the heated zones, or if a liquid sample
has been pulled into the system, the GC and Transfer Line may need to be
replaced.