Petroleum and associated fractions present a unique challenge for mass spectrometric (MS) analysis, as they are commonly comprised of tens of thousands of species that span a wide range of concentration and chemical functionality, so direct (dilute-and-shoot) analyses are plagued by selective ionization and limited dynamic range. Thus, online chromatographic separation prior to MS analysis is desired. However, due to the co-elution of abundant sulfur-, oxygen-, and nitrogen-containing species (sample complexity), mass resolving power &gt;400K (at m/z 400) is required to unambiguously resolve and identify elemental compositions. Such performance is currently provided by Fourier Transform Ion Cyclotron Resonance (FT-ICR) mass spectrometers; however, only the highest magnetic field instruments can deliver high performance at a scan speed commensurate to that required for liquid chromatography (LC).<br/>Here, we demonstrate the utility of LC ultra-high resolution MS to expose the molecular-level complexity of a vacuum gas oil (VGO; 371-510 C), Canadian bitumen heavy distillate (550-600 C), and a series of upgraded and partially upgraded bitumen samples via online chromatography coupled to 21 T FT-ICR MS. Complex, single-scan mass spectra (&gt; 7,000 assigned molecular formulas) with signal-to-noise ratio ~400:1 at a mass resolving power ~1.5M (at m/z 400) are obtained. Similar results were previously possible by averaging 50-200 scans, but here are realized for single scans (one every 3.5s) in an 80 minute LC-MS experiment. The dual column chromatographic separation prior to FT-ICR MS resolves compounds by number of fused aromatic rings. Online MS analysis provides isomeric resolution between aromatic ring classes (i.e., compounds with the same elemental formula are observed in 2 or more ring fractions), as well as isomers within individual ring fractions. Direct infusion analysis of chromatographic fractions (off-line) were compared to online LC-MS results, but fail to capture the compositional trends within ring classes that are readily accessible by online LC-MS. The analyses provided unprecedented molecular-level insight into the chemical and structural complexity of these samples; it identified &gt;400,000 species (at the level of elemental composition assignment) in the heavy bitumen distillate.

Dual column on-line liquid chromatography coupled to ultrahigh resolution 21 T FT-ICR mass spectrometry for the determination of molecular-level changes in petroleum samples

256th National Meeting (2018)

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