Rapid sequential separation of sedimentary lipid biomarkers via selective accelerated solvent extraction

Accelerated solvent extraction (ASE) can be adapted for selective and sequential separation of saturated hydrocarbon, unsaturated/aromatic hydrocarbon and polar lipid fractions from complex organic extracts in environmental matrices. ASE extraction cells were packed with a layer of Ag+ impregnated and activated silica gel, followed by an aliquot of the total lipid extract, and topped with another layer of activated silica gel. A fraction containing saturated hydrocarbons (FSAT) was eluted with hexane. Then, cells were inverted for reversed solvent flow and compounds of increasing polarity were eluted with solvent of increasing eluotropic strength to yield an unsaturated/aromatic hydrocarbon fraction (FARO) separated from a polar lipid fraction (FPOL). Gas chromatography–mass spectrometry analysis demonstrated high recovery of standards in FSAT (90 ± 3%), FARO (82 ± 4%) and FPOL (87 ± 3%). Average compound recovery and efficiency of separation between lipid fractions were significantly improved (p < 0.05) relative to separation with gravity column chromatography using similar stationary phases. Overall, this selective extraction method affords reliable, semi-automated separation of compound classes in total lipid extracts according to saturation and polarity and is well suited for molecular characterization and compound-specific isotopic analysis.