State-of-the-art mass spectrometry with ultraviolet (UV) photoionization is mostly limited to time-of-flight (ToF) mass spectrometers with 1000–10 000 m/Δm mass resolution. However, higher resolution and higher spectral dynamic range mass spectrometry may be indispensable in complex mixture characterization. Here, we present the concept, implementation, and initial evaluation of a compact ultrahigh-resolution mass spectrometer with gas-phase laser ionization. The concept is based on direct laser photoionization in the ion accumulation and ejection trap (C-trap) of an Orbitrap mass spectrometer. Resonance-enhanced multiphoton ionization (REMPI) using 266 nm UV pulses from a frequency-quadrupled Nd:YAG laser was applied for selective and efficient ionization of monocyclic and polycyclic aromatic hydrocarbons. The system is equipped with a gas inlet for volatile compounds and a heated gas chromatography coupling. The former can be employed for rapid system m/z-calibration and performance evaluation, whereas the latter enables analysis of semivolatile and higher-molecular-weight compounds. The capability to evaluate complex mixtures is demonstrated for selected petrochemical materials. In these experiments, several hundred to over a thousand compounds could be attributed with a root-mean-square mass error generally below 1 ppm and a mass resolution of over 140 000 at 200 m/z. Isobaric interferences could be resolved, and narrow mass splits, such as 3.4 mDa (SH4/C3), are determined. Single laser shots provided limits of detection in the 20-ppb range for p-xylene and 1,2,4-trimethylbenzene, similar to compact vacuum REMPI-ToF systems.

In the past decade, extensive molecular-level research on asphaltenes, primarily based on mass spectrometric approaches, acknowledged the coexistence of two primary architecture motifs, “island” single-core- and “archipelago” (multi-core)-type structures. Nonetheless, analytical methods for a classification are still limited. In this study, the thermal desorption and pyrolysis behavior of a diverse set of asphaltenes covering island- and archipelago-enriched samples and their extrographic fractions has been investigated by a thermal-optical carbon analyzer (TOCA) hyphenated to high-resolution mass spectrometric evolved gas analysis. The capability of the TOCA for a temperature-resolved quantification of the released carbon is used together with the option of applying an inert or oxidative atmosphere. We found that the relative proportion of organic carbon emitted under an inert atmosphere and below 580 °C (OCdes/pyr) and the organic carbon released at elevated temperatures (>580 °C) and oxidative atmosphere (OCpyrogen) can be used as a classification approach for the prevalent architecture motif. This finding is likely caused by differences in the coking and charring behavior dependent on molecular structure. Hypothetically, single-core constituents will form more resistive shot-like coke due to their larger aromatic cores, whereas multi-core constituents seem to produce easier combustible sponge-like coke. Simultaneously, resonance-enhanced multiphoton ionization (REMPI), a soft ionization scheme particularly selective and sensitive for aromatic constituents, together with Orbitrap Fourier-transform mass spectrometry, allowed for time/temperature-resolved in-depth insights into the evolved chemistry. The alkylation pattern/length of the mass spectra received in OCdes/pyr (480/580 °C) fractions has been identified as a classification measure with lower and more narrow patterns for the asphaltenes dominated by single-core species. However, grouping based on the quantified TOCA results has been significantly more striking. Conclusively, TOCA of asphaltenes and their extrographic fractions can be used for structural classification as well as insights into coprecipitated maltenes, presumably also successfully applicable in future studies on residues from renewable oil sources.

The comprehensive chemical description of air pollution is a prerequisite for understanding atmospheric transformation processes and effects on climate and environmental health. In this study, a prototype vacuum photoionization Orbitrap mass spectrometer was evaluated for field-suitability by an online on-site investigation of emissions from a ship diesel engine. Despite remote measurements in a challenging environment, the mass spectrometric performance could fully be exploited. Due to the high resolution and mass accuracy in combination with resonanceenhanced multiphoton ionization, the aromatic hydrocarbon profile could selectively and sensitively be analyzed. Limitations from commonly deployed time-of-flight platforms could be overcome, allowing to unraveling the oxygen-and sulfur-containing compounds. Scan-by-scan evaluation of the online data revealed no shift in exact m/z, assignment statistics with root mean square error (RMSE) below 0.2 ppm, continuous high-resolution capabilities, and good isotopic profile matches. Emissions from three different feed fuels were investigated, namely, diesel, heavy fuel oil (HFO), and very low sulfur fuel oil (VLSFO). Regulations mainly concern the fuel sulfur content, and thus, exhaust gas treatment or new emerging fuels, such as the cycle-oil-based VLSFO, can legally be applied. Unfortunately, despite lower CHS-class emissions, a substantial amount of PAHs is emitted by the VLSFO with higher aromaticity compared to the HFO. Hence, legislative measures might need to take further chemical criteria into account.