Installation manual

Operating in Electron Impact (EI) Mode 3
5975 Series MSD Operation Manual 73
To measure column flow linear velocity
With capillary columns, such as those used with the MSD, linear velocity is
often measured rather than volumetric flow rate.
Procedure
1 Set Data Acquisition for splitless manual injection and selected ion
monitoring (SIM) of m/z 28.
2 Press Prep Run on the GC keypad.
3 Inject 1 µL of air into the GC inlet and press Start Run.
4 Wait until a peak elutes at m/z 28. Note the retention time.
5 Calculate the average linear velocity.
Average linear velocity (cm/s) =
where:
L = Length of the column in meters
t = Retention time in seconds
Be sure to account for any pieces of column broken off. A 1-meter section
missing from a 25-meter column can yield a 4% error.
6 Use this velocity to verify the MSD ChemStation flow calculations (page 74).
If the numbers disagree, click Change to calibrate the column dimensions.
7 To calculate the volumetric flow rate.
Volumetric flow rate (mL/min) =
where:
D = Internal column diameter in millimeters
L = Column length in meters
t = Retention time in minutes
100 L
t
--------------
0.785 D
2
L
t
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