Varian 4000 GCMS, Руководство по установке

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Section 8. Achieving External PCI
Specifications
The PCI specification for a 4000 GCMS system in External mode:
•
20:1 RMS signal-to-noise using the m/z 183 ion from a 1 µL injection of a
50 pg/µL BZP solution (03-920305-00). The required CI reagent is high
purity (> 99.95%) methane.
8.1 Install Gaseous CI
Before introducing methane into the CI plumbing it may be necessary to
condition the CI plumbing to remove air and water by opening the CI solenoids in
Manual Control. Install or convert to gaseous CI according to the instructions in
the CI Kit. The external PCI specification test run 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.
8.2 Adjust Gaseous CI Reagent Flow
Turn the CI needle valve behind the MS front door counter clockwise (CCW) until
it stops. Go to the Checks and Adjustments tab in Manual Control and select CI
Gas Adjustment as shown in Figure 6.2. Be sure to select
Methane
as the
Reagent and click
Start
. Slowly turn the CI needle valve behind the MS front
door clockwise (CW) until ion signal begins to show in the spectral window.
Continue turning the CI needle valve CW only as long as the m/z 29 signal
intensity increases. Once the signal intensity of m/z 29 has maximized further
CW turning of the CI needle valve will degrade system performance by
introducing hydrocarbon background. Typically, an Ion Gauge Pressure of 30 to
70 µTorr will be displayed when a proper adjustment is achieved as shown in
Figure 8.1. The current factory recommendation is 50 uTorr. Click
Done
when
finished.