Gas pressure

I have a 5975c GC and need to get rid of the excess air and water how much do I need to increase my split to remove the excess water from the WCOT column?

  • How long has the MS been pumping down?  If there is air/water in the MS, like after venting, maintenance, and pumping it down, that should be gone in 12-24 hours and typically less.

    The gas, plumbing, filters, inlet subsystem, and column are a different story.  It depends where the air/water are coming from. If the gas is contaminated it will never go away.  If the gas is contaminated and the filter is full it will never go away.  If there is only air/water in the inlet and column after maintenance or replacement, then after pumping down set the inlet to SPLIT mode, oh - 60ml/min total flow, the column flow to 2ml/min - that's safe for systems with either turbo pumps or diffusion pumps, with the inlet and transferline heated and the oven at your normal analytical method final oven temperature as long as that is hotter than 100°C. There is rarely a reason to bake a column higher than your analytical method's final oven temperature.

    Split flow does not go through the column, just the inlet. That's why you would increase the column flow to 2ml/min if you think there's water stuck in there. 

    If after an hour of that there is still air/water -- you need to cool things down and start leak checking. If maintenance was just performed, like source cleaning, column trimming or replacement, inlet liner and septum replaced, etc, then it's possible that a leak was introduced. The smartest thing then is to go back and do all of those tasks again, taking extra care with seals and O rings.  Too many overtighten the septum or MS column transferline nut and create leaks.

    and let us know.

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