CHARACTERIZATION OF COMPLEX HYDROCARBON MIXTURES USING ONLINE COUPLING OF SIZE-EXCLUSION CHROMATOGRAPHY AND NORMAL-PHASE LIQUID-CHROMATOGRAPHY TO HIGH-RESOLUTION GAS-CHROMATOGRAPHY

An on-line coupling of size-exclusion chromatography (SEC), normal-pha se liquid chromatography (NPLC), and gas chromatography (GC) for the c haracterization of complex hydrocarbon mixtures is described, The hyph enated system separates according to size, polarity, and boiling point , The use of size exclusion as the first separation step allows for th e direct injection of complex (''dirty'') samples without prior clean- up, SEC-NPLC coupling was realized using an on line solvent evaporator based on fully concurrent solvent evaporation (FCSE) using a modified loop-type interface, vapor exit and co-solvent trapping, Complete rec oncentration of the analytes was realized by the introduction of a cry ogenic cold trap, For the subsequent hydrocarbon group-type separation an amino-silica column with n-heptane as eluent was used, The NPLC-GC coupling was based on an on-column interface using partially concurre nt solvent evaporation (PCSE) and an early vapor exit, Initial results obtained on the analysis of a residue from the atmospheric crude-oil distillation (a so-called long residue) are presented as an example of the enormous separation power of the SEC-NPLC-GC system. The applicat ion of the system for quantitative analysis has not yet been studied.