Chromatography Forum

Hi everyone,
There is something weird that happened to the GC-MS I am using. There is a small air leak since last week, and I working on it. However, I find something really wired, when I press the pre run and profile 28 N2 and 32 O2 and 18 H2O via manual tune, the amount of all those 3 ions crazily increased. and the total flow is less than column flow 1ml/min + purge flow 3min/l. The inlet is in splitless mode, 200C.
I really appreciate any suggestions.
Best

If the flows are reading incorrect numbers, maybe something is wrong the the flow controller and air is being pulled back into the inlet by the vacuum of the MS. If you remove the column and put in a ferrule with no hole in it and the air and water go away in the MS then it is probably something before the column.

If you don't have a ferrule with no hole, then you could remove the inlet end of the column and cap it by inserting it into a septa, the seal will be good but not perfect.

If the flows are reading incorrect numbers, maybe something is wrong the the flow controller and air is being pulled back into the inlet by the vacuum of the MS. If you remove the column and put in a ferrule with no hole in it and the air and water go away in the MS then it is probably something before the column.

If you don't have a ferrule with no hole, then you could remove the inlet end of the column and cap it by inserting it into a septa, the seal will be good but not perfect.

Thank you very much. After I isolated the MS I found the problem is from the GC part, so I took off the column, sealed the inlet and purge flow outlet, the pressure of the system dropped much faster than the manual marked. Then I realize either the EPC or the gas line has a problem.
I wonder how to check the flow valves of EPC and how to do the maintenance. Thank you again for your reply.