|Assessing 2-Dimensional Comprehensive Flow-Modulated Gas Chromatography for fingerprinting archaeological bitumen
|Comprehensive Chromatography - The State of the Art
|Dr Thomas Van de Velde
|Prof Peter Vandenabeele
Prof Frederic Lynen
Abstract Information :
Biomarker analysis by means of GC-MS has been the standard for years in oil-spill analysis, sourcing unknown hydrocarbons and environmental assessments. The techniques developed for this practice, however, do not limit themselves to present-day issues: the same analytical techniques have proven to be very useful to acquire archaeological and historical knowledge. Bitumen, currently mainly a by-product of petroleum exploration and –drilling, has been used by mankind extensively for over six thousand years. This material outcrops naturally at specific locations (o.a. in southwest Iran and Iraq) where it could be easily collected. It has been archaeologically attested that the first international seaborne export of bitumen, a petroleum-related product, occurred around 4000 B.C.
In the last couple of years, comprehensive 2D-GC has been increasingly used to identify biomarkers in petroleum quite successfully. The advantages include the potential for higher peak capacity, signal enhancement due to analyte refocusing, the ability to produce structured chromatograms, and easier compound separation. In fact, comprehensive GC manages to separate highly-related molecules which are inseparable by conventional 1D-GC. Examples of such compounds, are 18α(H)-, 18β(H)-oleanane & lupane. Additionally, the identification of methylhopanes in petroleum have recently been acknowledged as holding potential for oil – source rock correlations. Comprehensive 2D-GC makes tentative separation of these compounds with their non-methyl counterparts possible and allows for a better identification and quantification of these compounds.
This project focuses on the use- and development of a GCxGC toolset specifically for the fingerprinting of bitumen; the main focus lies in the identification- and quantification of source rock-related biomarkers, such as oleanane for instance. Quite specific to the use of comprehensive GC, is the modulator. Typically, a cryogenic modulator is used in-between columns. Although effective, this setup is quite costly and complex in nature. We choose to experiment with a flow modulator and a variety of columns in order to obtain detailed biomarker identification for fingerprinting archaeological samples. The main focus points in this work are:
- Separation of hopanes in archaeological bitumen
- Column evaluation in both dimensions
- Evaluation of the potential of Polymerized Ionic Liquid (PIL) and of other polar columns specifically for the separation of hopanes
- The (dis-) advantages of flow modulation for target-specific hopanes
- Method optimization in regard to fingerprinting archaeological bituminous materials