Chromatographic techniques for petroleum and related products

Recent developments in chromatographic techniques for the separation and quantitative characterization of petroleum and related products are highlighted. Specifically, scope, applicability, and versatility of individual techniques such as gas chromatography, liquid chromatography, supercritical fluid chromatography, thin-layer chromatography, and size-exclusion chromatography are discussed in some detail. In general, analytical approaches vary widely depending on the chromatographic technique, instrumentation, minimum detection limit, and sample type. Specific applications include chromatographic separation followed by identification and determination of individual components, measurement of boiling range distribution, and determination of hydrocarbon group types. With the exception of gaseous samples and light distillates (up to gasoline range materials), the inherent complexity arising from the presence of numerous isomers and compound types, and the finite resolution afforded by chromatographic methods preclude precise identification and quantitative determination of individual components in fossil fuels and oils. For the middle and heavy distillates, chromatographic techniques have been applied mostly for the isolation and determination of compound classes. Several techniques such as open-column liquid chromatography, medium pressure liquid chromatography, high-performance liquid chromatography, and supercritical fluid extraction provide separation of compound classes for subsequent characterization by high-resolution chromatography, spectroscopy, or other methods. Hyphenated or multitechnique chromatographic approaches have also been described. These simplify the characterization of complex samples by incorporating multiple separation mechanisms and detection schemes.