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Section 9. Achieving External NCI
Specifications
If necessary, install or convert to gaseous CI according to the instructions in the
CI Kit. This external NCI acquisition should be performed using 25 psi line
pressure of high purity methane as the CI reagent gas. High purity (at least
99.95%) methane gas is recommended to minimize source contamination. Set
the gas flow rate according to the instructions in Section 8.2 of this document.
The NCI specifications for a 4000 MS upgrade in External mode:
•
50:1 RMS signal-to-noise using the m/z 362 ion from a 1 µL injection of a
1 pg/µL DFB solution (03-931130-01).
9.1 Methodology
NOTE: The 4000 GCMS system will arrive with a CD containing factory test
method and data files. These method files can be used to pass the sensitivity
tests associated with the installation. Retain the test files CD for your records.
Ensure the MS temperatures are set for this acquisition:
•
Trap: 150 °C
•
Manifold: 40 °C
•
Transfer Line: 230 °C
•
Source: 150 °C
In System Control, activate the external NCI method from the Test Files CD.
The appropriate MS damping gas flow rate is embedded in the name of the
corresponding data file found on the Test Files CD included with the system. The
Damping Gas flow rate can also be found in the Data File Information dialog in
the Module Attributes section. Set the MS damping gas flow rate to this value to
ensure optimal system performance. Refer to section 2.1 for help in
programming the MS damping gas flow rate.
9.2 DFB Acquisition
Use the Inject Single Sample option to make a 1 µL manual injection of test mix
03-931130-01. Use a lower air gap to avoid sample loss through the tip of the
needle. Inject slowly (1 µL/sec) to avoid sample loss through explosive
vaporization. Ensure the split valve has changed from opened to closed before
injecting by striking the injector auto-start switch with the syringe barrel before
depressing the syringe plunger.
Summary of Contents for 4000 GCMS
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