Characterization of Molecular Mass Ranges of Two Coal Tar Distillate Fractions (Creosote and Anthracene Oils) and Aromatic Standards by LD-MS, GC-MS, Probe-MS and Size-exclusion Chromatography

Abstract

Laser-desorption mass spectrometry (LD-MS) method development was undertaken to improve estimates of mass ranges for complex hydrocarbon mixtures. A creosote oil, an anthracene oil, and a mixture of known polynuclear aromatic hydrocarbon (PAH) compounds were examined. The data on the mixture of the four PAHs made it possible to define LD-MS conditions necessary to generate artifacts such as cluster ions by the combination of high laser power and high-mass accelerator voltage. The formation of cluster ions was possible without overloading the detector system. These multimer ions overlapped with higher-mass ion signals from the sample. However, careful balancing of sample concentration, laser power, total ion current, and delayed ion extraction appears to show high-mass materials without generating high-mass multimer (artifact) ions. It is possible to suppress the formation of cluster ions by keeping low target concentrations and, consequently, low gas phase concentrations formed by the laser pulse. The principal method used in this work was the fractionation of samples by planar chromatography followed by successive LD-MS analysis of the separated fractions directly from the chromatographic plates. This method separated the more abundant small molecules from the less abundant large molecules to permit the generation of their mass spectra independently, as well as reducing the concentration of sample by spreading over the PC-plate. The technique demonstrably suppressed multimer formation and greatly improved the reproducibility of the spectra. Results showed the presence of molecule ions in the ranges m/z 1000−2000 for the anthracene oil sample and m/z 600−1500 for the creosote oil sample, tailing off to m/z ∼5,000. The creosote oil contained significantly less of this high-mass material than the anthracene oil sample, and in both cases, high-mass material was only present in low quantities. Ion mass range estimates were in close agreement with molecular mass ranges from size exclusion chromatography, and findings were consistent with changes observed in the UV-fluorescence spectra. The method outlined in the paper appears directly applicable to the characterization of heavier coal and petroleum derived fractions.

Characterisation and feasibility as carbon fibre precursors of isotropic pitches derived from anthracene oil

“…According to previous studies, this difficulty in the ionization is more acute in highly polydisperse samples, which seems to be the case in these fractions [9,15]. This effect is particularly noticeable when comparing the LDI-MS upper limit for the whole samples (around 12,000 m/z) with the upper limit of the PI fractions (about 20,000 m/z).…”

“…Several complementary analytical techniques have been used in order to glean information about molecular mass distributions, chemical structures and compositions [9], with a particular emphasis on the characterisation of the heavier fractions in the pitch, which mostly contain compounds above the mass range amenable to analysis by gas chromatography-mass spectrometry (GC-MS).…”

Application of mass spectrometry in the characterization of chemicals in coal‐derived liquids

“…Therefore, separation methods, such as distillation, liquid‐liquid extraction, and column chromatography, have been applied to facilitate the compositional characterization of coal tar by GC/MS and fine separation of valuable chemicals such as condensed arenes and phenols (Morgan et al, ; Long et al, ; Pan et al, ; Yao et al, ; Li et al, ; Jiao et al, ,b; Sun et al, ). Two coal tar distillate fractions, i.e., creosote oil (100–300 °C boiling range) and anthracene oil (250–370 °C boiling range), were analyzed with GC/MS (Morgan et al, ). The results show that phenols and n ‐alkanes are major components in creosote oil, while anthracene oil is mainly composed of condensed arenes varying from naphthalene to benzo[ g , h , i ]perylene with phenanthrene the most abundant.…”

“…Due to the high complexity in molecular compositions of crude coal tar, the chromatographic peaks of various compounds with similar structures or physicochemical properties overlap in GC/MS analysis. Therefore, separation methods, such as distillation, liquid-liquid extraction, and column chromatography, have been applied to facilitate the compositional characterization of coal tar by GC/MS and fine separation of valuable chemicals such as condensed arenes and phenols (Morgan et al, 2008;Long et al, 2012;Pan et al, 2012;Yao et al, 2012;Li et al, 2013b;Jiao et al, 2015a,b;Sun et al, 2015). Two coal tar distillate fractions, i.e., creosote oil (100-300˚C boiling range) and anthracene oil (250-370˚C boiling range), were analyzed with GC/MS (Morgan et al, 2008).…”

Characterization of Tars from the Thermal Processing of Baganuur and Tavan Tolgoi Coals from Mongolia, Using SEC, UV-F, IR and Mass Spectrometry

“…In more recent work [34][35][36][37][38] analytical plates from Whatman with flexible backing have been used. In this work, the developed plate could be either scraped to allow recovery of the fraction into solution or cut into small pieces to allow selected fractions to be stuck onto the laser target plate of the Bruker mass spectrometer for direct laser desorption from the silica surface.…”