Chromatography Forum

Update.

Blank vegetables sample answered one question. Yes, contamination appears during sample preparation. Unfortunately. And my only idea of it's origin is plastic bag compounds interference. (Have tried all solvents and cleanup gels but found no contamination.) My blank samples are stored frozen in plastic bags.
Good news are now one of columns separates this compound as not endrine, but something very alike to it. Maybe only untill pesticide standart is added.
Something (in the region of endrine separation "field") still accumulates during machine rest time inside the columns and separates during conditioning cycle.

It sounds like it may be a Phthalate. Could be in your sample prep vessels, solvent, Sodium Sulfate or other sample prep chemical, process, container or even the sample jar itself. I would take each of the steps individually, through the sample prep process to eliminate.
Good Luck,
Bill