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A clean-up method for organochlorine compounds in fatty samples based on normal-phase liquid chromatography (NPLC) is described. To this end, an existing clean-up procedure which uses column switching for the separation of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) from the fat matrix was simplified to a single silica LC column procedure. The use of an LC column packed with 3 microns silica enables complete fat/OCP separation in a total fraction volume of 12 ml, and results in a fully automated clean-up procedure that takes only 32 min per sample. The method showed average recoveries of 80-110% in the concentration range of 1-510 micrograms/kg, with relative standard deviations of less than 10%. Limits of determination were in the range of 0.5-50 micrograms/kg. The simplified approach has shown its potential for a variety of samples, such as milk, pork fat, animal feed and cod liver oil, showing its general applicability to fatty samples.

The advantages and drawbacks of coupled chromatographic techniques are discussed on the basis of selected applications of LC-LC and LC-GC in the analysis of pesticide residues applied to environmental and biological samples.