High Resolution Multidimensional Chromatographic Analysis of Hydrocarbon Distillate Fuels: Matrix Simplification Using Off-Line Preparative HPLC/DCD with On-Column GC/MSD and GC/FID
Hydrocarbon group-type fractionation of complex hydrocarbon mixtures can yield simplified samples amenable to detailed analysis by ancillary techniques. The present research focuses on a methodology for separating and quantifying a large number of the major and minor acyclic paraffins, naphthenes, aromatics, and olefins in selected gasolines and kerosenes. High-performance liquid chromatography (HPLC) with a dielectric constant detector (DCD) and analytical columns can yield accurate group-type quantitation. Substituting preparative-size columns into the HPLC system will permit separation and collection of these group types in fuels having distillation end points (ASTM D2887) of at least 300°C. One-dimensional analysis of these fractions, such as by high resolution capillary gas chromatography (GC), can yield data that is more reliable than that obtained from an injection of the whole fuel. The summation of the identified and quantified components in a fraction can be compared to the original group-type analysis of the whole fuel through the use of internal standards. The absolute amount and carbon-number distribution of the unidentifiable species and the fraction of undetected hydrocarbons can thus be obtained.