Sequential Extraction of Petroleum Asphaltenes with Magnesium Oxide: A Method To Reduce Complexity and Improve Heteroatom Identity

Sequential extraction of an asphaltene sample with magnesium oxide nanoparticles provides an approach to remove selectively molecules from a complex fraction. This method of extraction relies, in part, on adsorption preferences for differing heteroatoms to leave weakly adsorbing sample constituents in a toluene solution. The extracted sample exhibits reduced complexity enabling more reliable identification of the remaining molecules in solution. Mass spectrometry (MS) data indicate a general bias for preferential removal of higher molecular weight species. This is supported by a shift in the average <i>m</i>/<i>z</i> ratio of the asphaltene distribution to lower <i>m</i>/<i>z</i>, as well as a decrease in the intensity observed for higher <i>m</i>/<i>z</i> ion signals, for higher extraction numbers. UV–vis absorption data corroborate MS data to provide an appreciable visual means to quantify sample uptake after several sequential extraction steps with MgO. Furthermore, both UV and MS data indicate a point of diminishing returns, after which subsequent extraction with MgO nanoparticles results in limited adsorption of remaining asphaltene constituents. The remaining asphaltene constituents can then be treated with NiO nanoparticles in order to identify molecules containing pyridyl functional groups. Implementation of a more exhaustive MgO extraction, prior to treatment with NiO, resulted in an improved method for profiling pyridyl-containing structures in a complex asphaltene mixture relative to previous work

Exploiting Metal Oxide Nanoparticle Selectivity in Asphaltenes for Identification of Pyridyl-Containing Molecules

Extraction efficiencies for a series of model compounds representing heteroatom functional groups believed to be present in asphaltenes were determined in batch extractions with a variety of metal oxide nanoparticles (Fe₃O₄, TiO₂, NiO, Co₃O₄, and MgO). Extraction efficiencies from toluene solution varied depending upon both the adsorbate and the type of metal oxide used for extraction. However, the adsorbate was found to be the most important factor governing selectivity, which generally followed the trend: benzoic acid ≫ pyridine ≈ phenol > pyrrole > thiophene ≈ diphenylsulfide ≈ benzophenone. An important exception to this trend was that MgO did not appreciably adsorb pyridine. The divergent adsorption behavior of pyridine on NiO (extraction efficiency = 82 ± 1%) and MgO (extraction efficiency = 0 ± 2%) was subsequently exploited to demonstrate a novel approach for profiling pyridine-containing molecules in an authentic asphaltene sample. Specifically, mass spectra of the asphaltene mixture were obtained before and after treatment with NiO or MgO and compared to identify peaks exhibiting reduced intensity after treatment with NiO but no appreciable change in intensity after treatment with MgO. Results of batch extraction studies with model compounds and elemental composition data deduced from accurate mass measurements support that these peaks likely correspond to (or minimally contain) a molecule(s) possessing a pyridyl functional group

Characterization of Slow-Pyrolysis Bio-Oils by High-Resolution Mass Spectrometry and Ion Mobility Spectrometry

Bio-oils produced from biomass pyrolysis are an attractive fuel source that requires significant upgrading. Before upgrade strategies can be developed, the molecular composition of bio-oils needs to be better understood. In this work, oily and aqueous fractions of bio-oils produced by slow pyrolysis of two feedstocks, pine shavings (PS) and corn stover (CS), were analyzed by negative electrospray ionization (ESI)-Orbitrap and ion mobility-time-of-flight mass spectrometry (IM-TOF-MS). Analyte ion signal was observed primarily between <i>m</i>/<i>z</i> 80 and 450 in the mass spectra of these samples. Mass defect analysis and collision-induced dissociation (CID) experiments performed on mobility-separated ions indicated a high degree of homology among bio-oil samples produced from both feedstocks. Oxygen-rich species having between 1 and 9 oxygen atoms and with double bond equivalents (DBEs) ranging from 1 to 15 were identified, indicating that catalytic upgrading will likely be required if slow-pyrolysis bio-oils are to be utilized as fuel. IM-MS and IM-MS/MS analysis of ions belonging to select CH₂-homologous series suggest that mass-mobility correlations and post-ion mobility CID mass spectra may be useful in defining structural relationships among members of a given Kendrick mass defect series

Occurrence of Pharmaceuticals and Personal Care Products in German Fish Tissue: A National Study

German Environment Specimen Bank (GESB) fish tissue samples, collected from 14 different GESB locations, were analyzed for 15 pharmaceuticals, 2 pharmaceutical metabolites, and 12 personal care products. Only 2 pharmaceuticals, diphenhydramine and desmethylsertraline, were measured above MDL. Diphenhydramine (0.04–0.07 ng g^–1 ww) and desmethylsertraline (1.65–3.28 ng g^–1 ww) were measured at 4 and 2 locations, respectively. The maximum concentrations of galaxolide (HHCB) (447 ng g^–1 ww) and tonalide (AHTN) (15 ng g^–1 ww) were measured at the Rehlingen sampling site in the Saar River. A significant decrease in HHCB and AHTN fish tissue concentrations was observed from 1995 to 2008 at select GESB sampling sites (<i>r</i>² = 0.69–0.89 for galaxolide and 0.89–0.97 for tonalide with <i>p</i> < 0.003). Galaxolide and tonalide fish tissue concentrations in Germany were ∼19× and ∼28× lower, respectively, as compared to fish tissue concentrations measured in a United States nationwide PPCP study conducted in 2006. Proximity of the sampling locations to the upstream wastewater treatment plant discharging point and mean annual flow at the sampling location were found to significantly predict galaxolide and tonalide fish tissue concentrations (HHCB: <i>r</i>² = 0.79, <i>p</i> = 0.021 and AHTN: <i>r</i>² = 0.81, <i>p</i> = 0.037) in Germany