Comparison of sulfuric acid treatment and multi-layer silica gel column chromatography in cleanup methods for determination of PCDDs, PCDFs and dioxin-like PCBs in foods

Abstract

Two typical cleanup methods, sulfuric acid treatment and multi-layer silica gel column chromatography, for the determination of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dioxin-like PCBs) in seventeen food samples were examined and compared. Vegetables, fruits, cereals, fish, meat and dairy foods were extracted by conventional methods (shaking with acetone/n-hexane or with n-hexane after alkaline treatment). The extracts were cleaned up by sulfuric acid treatment or multi-layer silica gel column chromatography, followed by several column chromatographic steps. Of the samples treated, the vegetable, fruit and cereal samples could be directly applied to the multi-layer silica gel column after extraction. However, the samples containing fats and oils such as fish, meat and dairy foods needed to be treated several times with concentrated sulfuric acid before multi-layer column chromatography, because these samples plugged the column with oily residues. Both cleanup methods gave similar values of isomeric concentrations and showed similar efficiency of purification, and the recoveries ranged from 40 to 120%. These results are considered to provide useful data for the efficient analysis of dioxins in foods which have wide-ranging compositions.