tailing issue for one peak type

I currently run on 6890 for leachable testing and use a leachable ID solution as a retention time marker. the marker contains diethylene glycol monobutyl ether(DGBE) and diethylene glycol butyl ether acetate (DGBA) in acetonitrile. however after maybe just one run the DGBE peak will start to tail badly and get worse while DGBA will remain consistent. im assuming this is an activity problem because of hydroxyl group? I've started using a ultra inert GC column with gaurd column and an ultra inert liner but the problem will always start up again. anything else in the flow path that can cause activity issue? anything i can change to slow/stop this tailing?

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  • It is an inertness problem and maybe something else. Be sure your injector is at 300 °C (low vapour pressure of your analytes) and what about your starting temperature? Is it maybe too low, so that you get condensation at the beginning of the guard column? (BTW real guard column or retention gap?)

    Anyway, everything UltraInert is good for this.

    Regards,

    Norbert

  • thank you, see below the last 3 runs of the LIS solution. the black one is the most recent and is developing a lump after the main peak. the guard column I am using is 10M ultimate plus deactivated fused silica tubing (part CP805310) connected to 30M DB-5 530mm ID main column. is this guard column the correct one to be using? is there other guard columns that provide better inertness? the starting temp of the oven is 35C. 

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  • thank you, see below the last 3 runs of the LIS solution. the black one is the most recent and is developing a lump after the main peak. the guard column I am using is 10M ultimate plus deactivated fused silica tubing (part CP805310) connected to 30M DB-5 530mm ID main column. is this guard column the correct one to be using? is there other guard columns that provide better inertness? the starting temp of the oven is 35C. 

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