Fractionation of polar organic constituents in environmental samples using the lipophilic dextran gels Sephadex LH-20 and Sephasorb HP Ultrafine : Application to a weathered Ekofisk crude oil

Abstract

A method has been developed for the enrichment and fractionation of trace amounts of polar organic constituents in environmental samples. The procedure involves two steps using the lipophilic gel filtration gels Sephadex LH-20 and Sephasorb HP Ultrafine in two different modes: (1) separation and isolation of alcohols, phenols, hydroperoxides, acids and highly polar components as a result of retardation of compounds containing hydroxyl groups on Sephadex LH-20 using stepwise gradients of chloroform, methanol and tetrahydrofuran as the mobile phase; (2) liphophilic-hydrophilic partitioning using Sephasorb HP Ultrafine swollen in methanol-water and eluted with stepwise gradients of n-hexane and benzene, which separates non-hydroxyl-containing constituents. The method leads to essentially quantitative recoveries of the different compounds, and is sufficiently rapid and convenient for use in routine analysis. Minimal degradation of the sample components occurs as this is a pure chromatographic procedure on highly inert gel matrices with no catalytic activity, avoiding the acid/alkali extractions and chromatography on more labile gel matrices that often accompany other procedures and usually alter the sample to some extent. The application of the method to a weathered Ekofisk crude oil is described.