This document describes the analysis of pesticide 1,2,3,4,5,6-C6H6Cl6 concentration in seafood samples using Agilent EnviroPrep and gel permeation chromatography (GPC). The EnviroPrep column, filled with a high-resolution macroporous packing material, was selected for separation. The column is made of stainless steel and can be used in any high-pressure liquid chromatography system. The macroporous packing material has a strong and permanent pore structure, providing excellent separation efficiency in non-sample loading-intensive analysis. The small pore size eliminates interference from high molecular weight compounds and maximizes separation efficiency.