Paraffin, Olefin, Naphthene, and Aromatic Determination of Gasoline and JP-4 jet Fuel with Supercritical Fluid Chromatography

A method that uses supercritical fluid chromatography (SFC) with flame-ionization detection (FID) to determine naphthenes (cycloparaffins), paraffins, olefins, and aromatics in gasoline and JP-4 jet fuel is developed. Four packed silica columns in series are used to isolate the aromatics and provide ring number distribution. In addition, the silica columns provide separation of paraffins from the coeluting olefins and naphthenics. The olefins are trapped on a silver-loaded strong cation-exchange silica gel column and removed by back-flushing. Good agreement is found between gas chromatographic hydrocarbon analysis and the SFC method. A relative standard deviation of 0.4% is found for a jet fuel with a naphthene content of 21.6 wt%. At a low naphthenic content of 1.0 wt%, a relative standard deviation of 3.0% is achieved for gasoline. Analysis times are typically 22 min.