Analysis of Heavy Fuel Oil Using Multi-Mode Ionization

Analysis of Heavy Fuel Oil Using Multi-Mode Ionization

Significance of the Topic

Heavy fuel oil is a complex residual mixture formed during petroleum distillation and cracking.
As a primary marine fuel, it faces stringent sulfur limits under IMO 2020 regulations to reduce environmental emissions.
Comprehensive chemical profiling is essential for regulatory compliance, fuel quality control, and environmental monitoring.

Objectives and Study Overview

This study demonstrates the application of comprehensive two-dimensional gas chromatography coupled with high-resolution time-of-flight mass spectrometry (GC×GC-HRTOFMS) and a Multi-Mode Source (MMS) for heavy fuel oil analysis.
Key goals include:

• Full characterization of volatile and semi-volatile fractions.
• Confident identification of sulfur- and nitrogen-containing species.
• Evaluation of electron impact (EI), positive chemical ionization (PCI), and electron capture negative ionization (ECNI) within a single setup.

Methodology and Instrumentation

• Sample Preparation: Heavy fuel oil diluted in dichloromethane; 2 µL pulsed splitless injection at 325 °C.
• GC×GC Conditions: Rxi-5MS primary column (30 m × 0.25 mm × 0.25 µm), Rxi-17SilMS secondary column (1.2 m coil) with 7 s modulation; temperature program 40 °C (5 min) to 330 °C at 4 °C/min; secondary oven and modulator +15 °C offsets.
• Mass Spectrometry: Pegasus HRT 4D with MMS; ion source at 250 °C (EI) and 165 °C (PCI/ECNI); mass range 30–1000 m/z; acquisition rate 200 spectra/s.
• Data Processing: ChromaTOF software with post-run calibration, automatic peak finding, NIST20 library search, and Identification Grading System (IGS) for hit ranking.

Key Results and Discussion

• IGS-Enhanced Identification: Combining retention index and high-resolution mass accuracy improved library assignments, illustrated by octadecane identification over similar isomers.
• Sulfur Speciation: Peak filtering isolated sulfur-containing species such as methyldibenzothiophene isomers, facilitating rapid assessment of sulfur content (<0.5% by mass).
• Molecular Ion Confirmation: PCI mode yielded molecular ions absent in EI; for example, 5-ethyldecane [M–H]+ at m/z 169.1952 with <2 ppm accuracy confirmed the molecular formula C12H25.
• Bulk Classification: Defined regions on the 2D chromatogram enabled quantitation of compound classes: paraffins (17.4%), naphthenes/cycloparaffins (41.7%), aromatics, hopanes, steranes, cyclosiloxanes, and unclassified species (22.6%).

Benefits and Practical Applications

• In-depth profiling of complex petroleum mixtures.
• Enhanced confidence in compound identification for environmental compliance.
• Efficient data filtering and visualization reduce analysis time.
• Single-source hardware allows seamless switching between ionization modes without venting.

Future Trends and Opportunities

• Integration of machine learning for automated peak classification and spectral deconvolution.
• Extension of the methodology to diverse environmental and industrial matrices.
• Combination with additional ionization techniques (e.g., APCI) to expand detectable compound ranges.
• Development of near real-time monitoring workflows for on-site fuel quality assessment.

Conclusion

The integration of GC×GC, high-resolution TOFMS, and multi-mode ionization provides unparalleled analytical power for both individual compound identification and bulk class characterization in heavy fuel oil. This approach supports regulatory requirements, enhances identification accuracy, and streamlines laboratory operations.

Reference

LECO Corporation. Analysis of Heavy Fuel Oil Using Multi-Mode Ionization. Application Note, Form No. 203-821-655 (2022).