Factors Affecting the Chromatographic Analysis of Asphaltic Petroleum and of Recent Marine Sediment Organic Matter

Abstract

This investigation was undertaken to define better some of the factors which influence the elution chromatography of rock and sediment organic matter containing high molecular weight components.The separation efficiencies of a normal paraffin hydrocarbon, n-octadecane-1 -C14, of an aromatic hydrocarbon, phenanthrene-9-C14, and of an aliphatic acid, octadecanoic-1 -C14 acid, in the presence of asphaltic petroleum or of Recent marine sediment organic matter have been determined on alumina columns. The presence of high molecular weight material on the columns caused the retention of some of the radioactive eluates beyond their normal points of effluence. Experimental evidence suggests association of asphaltic material with at least some of the Cl4-labeled substances. The relative inefficiency of chromatographic separations of the three tracer compounds was noted even in the absence of bituminous material.Chromatography is one the primary tools in the analysis of petroleum and of Recent marine sediment organic matter. The chromatographic analysis of petroleum distillate fractions is now routine; separation efficiencies in distillate fractions have been studied by Fink, Lewis, and Weiss (S), among others. In certain types of investigations, however, such as in geochemical studies, it is desirable to work with samples in their original state rather than with distillate fractions. This poses some difficulty because, as Witherspoon (10) has shown, crude petroleum has colloidal components. Winniford (9) reported that the molecular weights of the asphaltene colloids may go as high as 300,000. These high molecular weight particles seem to interfere with the chromatographic separations of petroleum constituents. Kleinschmidt (S), therefore, suggested the removal of the asphaltenes

Routine Separation and Determination of Total Saturated Hydrocarbons in Heavy Petroleum Samples by Adsorption Chromatography.

“…Preseparation of both the bottoms fraction and the blend by benzene elution from 4% H20-A1203, as described in the experimental section, followed by normal separation gave quantitative recoven-of the blended saturates (assuming constant recovery of the original bottoms sample saturates in each separation), a result seemingly contradicted by the work of Hamwa\et ol. (7). It appears to the authors that some of the results of Hamway et al (7) on asphaltic samples may be explained by slow dissolution of the asphaltic sample blends, wdth retention of saturates within solid or semisolid sample particles.…”

“…(7). It appears to the authors that some of the results of Hamway et al (7) on asphaltic samples may be explained by slow dissolution of the asphaltic sample blends, wdth retention of saturates within solid or semisolid sample particles. In any event, Low viscosity lubricating oil sample, 1 to 1000 oil-gel ratio it seems that asphaltic samples preseparatecl as above give quantitative saturate recoveries.…”

“…The suggestion of Hamwav, Cefola, and Nagy (7) with respect to the possible holdup of saturates on the column past the departure of the normal elution band was also investigated. The nonsaturate fractions (B plus C) from several of the above separations were reseparated by the routine procedure; their saturate contents were thus determined.…”

“…The possible occlusion of saturates in residual, asphaltic samples was also studied in view of the observations of Hamway, Cefola, and Nagy (7) on the possible "association of saturates and asphaltenes." A distillation bottoms fraction (670°F .…”

“…As an additional complication in assessing the accuracy of prior EAC saturates methods, a recent communication (7) has cast uncertainty on the accuracy of all EAC saturates procedures, particularly for high boiling samples. It is claimed that the elution of saturated and other pure hydrocarbons from alumina is frequently incomplete, part of the compound remaining on the column after the normal elution band appears to have cleared the column.…”