CI Reagent Gas Requirements
These paragraphs give the requirements for the reagent gases used for CI
operation with the 4000 MS. The following reagent gases are recommended:
methane and isobutane.
Use high-purity reagent gas for maximum sensitivity and good spectral quality.
Impurities can react with sample ions, creating confusing mass spectral data.
The amount of reagent gas consumed during CI operation is very low (typically 1
to 2 mL/minute). Depending upon how much CI you plan to do, choose the size
of the gas cylinder appropriately.
The requirements for the recommended gases are as follows:
Methane
Methane should have a purity of 99.99% or better. Use a gas cylinder with
a two-stage pressure regulator that has a stainless steel diaphragm and
maximum inlet pressure of 30 psi (200 kPa).
Isobutane
Isobutane should have a purity of 99.99% or better. Use a gas cylinder
with a two-stage pressure regulator that has a stainless steel diaphragm
and maximum inlet pressure of 30 psi (200 kPa).
The CI reagent gas should contain less than 1 ppm of water. Water in the CI
reagent gas may interfere with CI operation.
If you need to use a longer line than the 4 mL/min restrictor alone, use pre-
cleaned copper or stainless steel gas lines for methane or isobutane. All gas
lines should be free of oil (and other contaminants) and preferably flame dried. If
possible, use the pre-cleaned copper tubing from the GC Start-Up Kit.
DO NOT flame! Dry the reagent gas lines with CI reagent gas present.
Setting Up the CI Reagent Gas Supply
Use the following procedure to set up the CI reagent gas supply.
CI reagent gases may be hazardous. Use proper protection when installing the
reagent gas.
1. Enter System Control and select the Manual Control tab dialog.
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