46
2 Operating the MSD
To measure column flow linear velocity
To measure column flow linear velocity
Materials needed:
Syringe
1 Set Data Acquisition for manual injection and selected ion monitoring
(SIM) of m/z 28.
2 Click
Prep Run.
3 Inject about 1 µl of air into the injection port and click
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/sec) =
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 value to verify the MSD ChemStation flow calculations (page 47).
If the numbers disagree, click the
Change button to calibrate the column dimen-
sions.
7 To calculate the volumetric flow rate.
Volumetric flow rate (ml/min) =
where:
D = internal column diameter in millimeters
L = the column length in meters
t = the retention time in minutes
100 L
t
---------------
0.785 D
2
L
t
------------------------------
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