Hello, I'm new here so this is my first post.
I have an issue with a valve on this chromatograph.
The system is set-up to analysis gas from Ethanol reforming, so to separate hydrocarbons, hydrogen, carbon dioxide and monoxide. To do the job a HP-PLOT/T and a molecular sieve column are used. In this system carbon dioxide poison the molecular sieve column, so a valve system is used.
I have two valves, one for injection (V1), and another (V3) that shut-off flux on molecular sieve, trapping the air/hydrogen/methane mixture in the molecular sieve. Like in this scheme (the methanator system was no longer in use).

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I’m working with a standard mixture with hydrogen/methane/carbon oxides/ ethane/ethene/methane, and started to observe a strange occurrence of two peaks after the valve 3 returns to off position that are air separated by the molecular sieve column. So I put the mobile phase (Argon) in line with the injector, and do the test. I’m still observing these two peaks after the valve returns.
In this chromatogram Valve 3 as set on at 2 and 7 min, and set of at 4 and 10 minutes, with argon injection in line.

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I don’t know what to do.
Do I need to change the valve’s rotor?
There is some kind of air leak entering in this system?

Thanks