Front edge peak shouldering

[LabProARW]

I have found quite a bit of information about peak fronting, however I am trying to develop a method and my chromatogram for my internal standard component is shouldering on the front end. Interesting that I don't find any good information about shouldering on the front of a peak. The fronting information gives a thorough description of what is going on inside the column, and mentions column overload as the main explanation.
All information is welcome on front edge shouldering.

Thanks,

[James_Ball]

I think that would still point to column overload, or inlet overload.

What type of injection are you doing, split or splitless?
What volume liner and head pressure are present at injection?

[LabProARW]

What type of injection are you doing, split or splitless?
What volume liner and head pressure are present at injection?

I am using a split injection 25:1 with a 4 mm split liner with glass wool. I am using a 30 M x 0.25 mm x 0.25 uF column and 8.2 head pressure and 0.9 ml min constant column flow. The solvent is methanol. My starting oven temp is 180C and inlet temp of 225C.

After consulting with an Agilent application specialist I lowered the starting oven temperature. This did the trick and took away the front peak shoulder on my diethylphthalate. Since this now works I sure would like to know the mechanics of why this worked and what is going on so I can visualize the problem and solution!

[Peter Apps]

I would guess some odd effect of transient inlet cooling as the methanol evaporates from the glass wool. The lower oven temperature focusses the distorted inlet band into a sharp band. If you are happy with the lower initial oven temperature then stick with it, if not then try increasing the inlet temperature, or changing the type of inlet.