Improved methods for separation and chromatographic analysis of natural asphalts

Abstract

The suitability of two standard bitumen recovery methods for the separation of a natural asphalt is examined and some modifications are proposed which lead to a clearer picture of the composition of this type of asphalt. The usefulness of a standard fractionation method for the recovered bitumen is then investigated and a procedure for obtaining sharper cut-off points between aromatic fractions is introduced. These fractions can then be further fractionated by simple gradient elution chromatography into less complex mixtures. The study showed that for natural asphalts and other asphaltic materials containing fine inorganic particles, consistent results could only be obtained through a modification of ASTM D2172-81. It was observed that ASTM D4124-86 gave consistent results only when cut-off points are precisely identified. Gas chromatography and synchronous excitation spectrofluorimetry showed that the additional fractionation of the aromatic consitituents is an important step before detailed analytical work can proceed.