AN ONLINE COUPLED HPLC-HRGC SYSTEM FOR THE QUANTITATIVE CHARACTERIZATION OF OIL FRACTIONS IN THE MIDDLE DISTILLATE RANGE

A commercially available HPLC-HRGC instrument was adapted to enable the full quantitative characterization of oil fractions in the range 150-400 degrees C. The HPLC separates the sample into five fractions: saturates, mono-aromatics, di-aromatics, fluorenes + dibenzothiophenes, and tri-aromatics. These fractions are subsequently quantitatively transferred via an on-column interface to the HRGC part of the system. This transfer is performed into an empty, wide-bore precolumn (retention gap), which enables a refocussing effect of the compounds of interest in the tail of the HPLC mobile phase, which acts as a solvent in the GC. A solvent vapor exit in the system enables the vent of the major part of this solvent. The final HRGC separation provides a carbon distribution of the saturates and the mono-aromatics and enables the identification of a number of compounds in the other three fractions. It is demonstrated that the described method is quantitative for the hydrocarbons, but also for sulphur-containing compounds in only those samples that have a low sulphur content. (C) 1995 John Wiley & Sons, Inc.