Discipline: Chemistry and Chemical Sciences
Subcategory: Chemistry (not Biochemistry)
Paolo Benigni - Florida International University
Co-Author(s): Mark E. Ridgeway and Melvin A. Park, Bruker Daltonics Inc, Billerica, MA Francisco Fernandez-Lima, Florida International University, Miami FL
Typically, the analysis of complex mixtures, such as crude oils and its degradation products, and dissolved organic matter, is limited to the low molecular weight fractions, or a broad range characterization of the sample by identifying the distribution of chemical formulas present in the sample. This analysis is typically one dimensional, because ultra-high resolution mass spectrometers have a much lower acquisition rate, making interfacing with gas/liquid chromatography challenging. Over the last years there has been an increase in the use of ion mobility spectrometry – mass spectrometry based tools for the separation and characterization of molecules within complex mixtures. Particularly, trapped ion mobility spectrometry has been coupled with ultra-high resolution mass spectrometry (e.g. FT-ICR MS) in order to combine the high resolution ion mobility separation with ultra-high resolution mass separation. The IMS-FTMS instrumentation permits the separation of a complex mixture in two dimensions, allowing for a better characterization of the isomeric content of the sample. Specifically, the developed methodologies can be used to analyze complex mixtures of polyaromatic hydrocarbons in a coal tar, the photo-degradation of the low energy water accommodated fraction (LEWAF), and samples of dissolved organic matter (DOM). This work also incorporates the use of unsupervised detection of molecular features in complex mixtures. Automated peak detection is challenging, requiring highly defined peaks in order to accurately identify the ion mobility for each chemical formula. Results shows the separation of different regions in the IMS-MS spectrum of the coal tar, separating the condensed aromatics from structures from the molecules with a greater aliphatic content. The distinction between the condensed aromatics and the aliphatics is also observed in the LEWAF samples, where photo-solubilization is observed after 16 hours of exposure to light, and after 115 hours, significant oxygenation of the condensed aromatics is observed. This leads to formation of molecules with 4-5 oxygens, which were previously not detected in the sample. In contrast to the coal tar and the LEWAF, the DOM samples are significantly different in their composition, with a much greater degree of oxygenation, and having different trend lines from the other two samples. Future steps of this work involve the addition of complementary theoretical calculations to generate candidate structures for the observed chemical formulas. That is, the use of the collision cross section measured by the TIMS is based on the three-dimensional structure of the molecule, therefore there is a limited number of potential structures.
Funder Acknowledgement(s): National Institutes of Health (Grant No. R00GM106414)
Faculty Advisor: Francisco Fernandez-Lima, email@example.com
Role: All of the work was performed by myself. Assembly of the instrumentation, analysis and data processing for all of the samples.