16 5977 Series MSD Operation Manual
1 Introduction
The CI hardware allows the 5977 Series MSD to produce high-quality, classical
CI spectra, which include molecular adduct ions. A variety of reagent gases
can be used.
In this manual, the term “CI MSD” refers to the G7040A MSD and upgraded
G7038A and G7039A MSDs. It also applies, unless otherwise specified, to the
flow modules for these instruments.
The 5977 Series CI system adds to the 5977 Series MSD:
• EI/CI GC/MSD interface
• CI ion source with an interface tip seal that can also be used with and
extractor EI ion source
• Reagent gas flow control module
• Bipolar HED power supply for PCI and NCI operation
A methane/isobutane gas purifier is provided and is required. It removes
oxygen, water, hydrocarbons, and sulfur compounds.
A high vacuum gauge controller (G3397B) is integrated in the system. Its use is
required for CI MSD and is recommended for EI also.
The MSD CI system has been optimized to achieve the relatively high CI ion
source pressure required for CI while still maintaining high vacuum in the
quadrupole and detector. Special seals along the flow path of the reagent gas
and very small openings in the ion source keep the source gases in the
ionization volume long enough for the appropriate reactions to occur.
The CI interface has special plumbing for reagent gas. A spring-loaded
insulating seal fits onto the end of the GC/MSD interface.
Switching back and forth between CI and EI ion sources takes less than an
hour, although a 1- to 2-hour wait is required to purge the reagent gas lines
and bake out water and other contaminants. Switching from PCI to NCI
requires approximately 2 hours for the ion source to cool.
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