Measuring polarity-based distributions (SARA) of bitumen using simplified chromatographic techniques

Among the different attributes that can be used to describe the chemistry of any given bitumen, the distribution of its constituent molecules based on polarity is strongly related to the bitumen's microstructure and engineering properties. Generally, bitumen is subdivided into asphaltenes and maltenes. The latter is further divided into three more fractions: saturates, aromatics and resins. This paper reviews the basic principles of liquid chromatography and presents a simplified technique for asphaltene-maltene separation and two new methods for maltene fractionation. The two methods for maltene fractionation are based on chromatographic principles. The first method applies the thin-layer chromatographic technique combined with optical fluorescent densitometry for separation and quantification. The second method utilises solid-phase extraction (SPE) cartridges, which are commercially available in pre-packed standard units and allow rapid and repeatable testing when used as a mini liquid chromatography column. Both methods are scalable to quantify more than three maltene fractions. The proposed methods were semi-quantitatively validated using 10 binders with known polar fractions. The simplicity, the minimal requirement of capital equipment and the monitoring time makes the proposed method an attractive option for use as a routine test to create a sizable database of bitumen fingerprints based on their polarity.