“…The main difficulty in these determinations is possible interferences from the substrate (fat, fatty acids, and proteins) as well as that analytes are at very low concentrations (traces). Usually they include Soxhlet extraction, 11,12 a time-consuming technique that requires large volumes of solvents, which is necessarily followed by a fat removal step. Fat removal is performed either by gel permeation chromatography (GPC) or by treatment with sulfuric acid.…”