Resolving the Unresolved Complex Mixture in Petroleum-Contaminated Sediments

Comprehensive two-dimensional gas chromatography (GC×GC) was used to investigate the chemical composition of the unresolved complex mixture (UCM) of hydrocarbons in petroleum-contaminated marine sediments. The UCM hydrocarbons were extracted and separated with silica and silver-impregnated silica gel chromatography to yield four fractions (branched alkanes and cycloalkanes, monoaromatics, naphthalenes, and multi-ring PAHs) prior to GC×GC analysis. GC×GC separations used a poly(dimethylsiloxane) stationary phase for volatility selectivity on the first dimension and a 14% cyanopropylphenyl polysiloxane phase for polarity selectivity on the second dimension to fully resolve monoaromatic, naphthalene, and multi-ring PAH compounds from the UCM. A chiral γ-cyclodextrin phase was used for shape selectivity on the second GC×GC dimension to resolve individual branched alkanes and cycloalkanes in the saturates fraction of the UCM. The ability of GC×GC to resolve thousands of individual chemical components from the UCM will facilitate an understanding of the sources, weathering, and toxicity of UCM hydrocarbons.