High-resolution mass spectral analysis of extremely complex mixtures commonly relies on direct “dilute and shoot” (+/-) electrospray ionization (ESI) FT- or FT-ICR mass spectrometry. However, this approach suffers from several known limitations that restrict detectable species in such complex, polyfunctional matrices. Foremost, selective ionization of more acidic (in (-) ESI) species limits detection of less acidic species, and most commonly results in the preferential ionization of lower molecular weight species. Furthermore, given the wide range of chemical functionalities / structural motifs in these complex mixtures, aggregation is always a concern and can similarly limit the detected species to a small (10-20%) mass fraction of the whole sample. Fractionation is a proven solution to mitigate the highlighted issues, but unsuccessful to date due to the polyfunctionality of many ultra-complex organic mixtures.
Herein, we address the mass spectral analysis of polyfunctional oxygenates commonly encountered in biomass pyrolysis (Energy) and dissolved organic matter (Environment) by on-line liquid chromatography coupled to high-field Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS). For the biomass pyrolysates, an additional extrography method (offline) was developed to expose gross compositional differences between pyrolysates before and after upgrading. In both applications, the developed online LC method successfully separated polyfunctional oxygen-containing species by carbon number, aromaticity, and oxygen content, which led to greater compositional coverage (measured as the number of detected / assigned molecular formula and the maximum / minimum H/C & O/C ranges) than direct analysis. The presentation will highlight the additional information afforded by the online LC, its ability to distinguish between sample origin / type, and potential applications in the areas of energy and environmental research. It will also discuss utilization of direct analysis over online LC for specific applications. Work supported by the NSF Divisions of Materials Research and Chemistry through 16-44779 and the State of Florida.
