Galvanic Applied Sciences AccuChrome MA2963, Operation Manual

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Revision 4 88 12/15/2018
Figure 7-3: Skimming Parameters indicate the Windows
in which the peak minima can be found
g) Verify the valve timing. There are 2 areas where drift in the retention times of the peaks
may cause problems with the valve actions.
• C6+ Back Flush - Chromatograph Valve 1(CV1) is turned ON to inject the contents of
the sample loop into Column 1. Nitrogen, Methane, Carbon Dioxide, Ethane, Propane,
iso-Butane, n-Butane, iso-Pentane and n-Pentane pass through Column 1 and into
Column 2. The flow of carrier gas through Column 1 is then reversed so that hexane
and heavier components are eluted through the detector as a composite peak. Ideally,
CV1 should be turned OFF when n-Pentane has eluted from Column 1 but the Hexane
has not. This point can be determined by setting the CV1 OFF time to a smaller than
normal value so that all or some of the n-Pentane gets back flushed from Column 1.
The time for CV1 OFF can then be increased in 1 second intervals. For each run
observe the area for the C6+ peak and the area for the n-Pentane peak. The CV1 OFF
time should be increased until the n-Pentane peak no longer increases and the C6+
peak does not decrease.
• Ethane/Propane Split - At this point in the run, Nitrogen, Methane, Carbon Dioxide,
and Ethane pass through Column 2 and into Column 3. Chromatograph Valve 2 (CV2)
is turned OFF so that Column 3 becomes isolated with Nitrogen, Methane, Carbon
Dioxide, and Ethane trapped inside. Column 2 continues to elute until Propane, iso-
Butane, n-Butane, iso-Pentane and n-Pentane are eluted through the detector. Ideally,
CV2 should be turned off when Ethane has eluted into Column 3 while Propane is still
in Column 2. If CV2 is turned off too soon, some or all of the ethane will stay in Column
2. This will cause an error in the amount of area integrated for ethane. If CV2 is turned
OFF too late, then some or all of the propane will elute into Column 3, causing an error
in the Propane area. The correct time for CV2 to be turned off can be determined by
decreasing the CV 2 OFF time so that the peak area for Ethane drops off. This time can
then be increased in 1 second intervals. For each run note the peak area for Ethane
and Propane. The CV2 OFF time should be increased until the Ethane peak area no
longer increases and the Propane peak are does not decrease.