Characterization of Complex Forensic Samples by Gas Chromatography–High Resolution Time-of-Flight Mass Spectrometry

Significance of the Topic

The ability to analyze complex forensic botanical samples with high accuracy and depth has growing importance in law enforcement and public health. Modern synthetic stimulants, naturally occurring intoxicants and herbal remedies exhibit extensive chemical diversity that challenges conventional methods. Comprehensive profiling supports substance identification, case resolution and development of analytical standards.

Objectives and Overview of the Study

This work aimed to establish a robust workflow based on gas chromatography coupled to high resolution time-of-flight mass spectrometry (GC–HR-TOFMS) for the discovery, confirmation and profiling of seized botanicals including marijuana, bath salts, khat, pokeweed and magic mushrooms. The goals included demonstration of headspace SPME for volatiles and solvent extraction with derivatization for non‐volatiles alongside high‐resolution deconvolution for confident compound identification.

Methodology and Instrumentation

Sample Preparation Methods

• Headspace solid phase microextraction of volatile constituents using DVB/CAR/PDMS fiber with saline or alkaline aqueous medium.
• Solvent extraction of nonvolatile components in methanol followed by derivatization via methoxyamine (MEOX) and N-methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA).
• Filtration, drying under N2 and transfer to GC vials.

Used Instrumentation

• LECO Pegasus GC-HRT high resolving GC–TOF mass spectrometer.
• Agilent 7890 gas chromatograph with Gerstel MPS autosampler.
• Restek Rxi-5 MS column (30 m × 0.25 mm × 0.25 µm).
• Helium carrier gas, EI at 70 eV, optional CI with ammonia/methane reagent.
• High resolution deconvolution software for spectral deconvolution and library search (NIST, Wiley).

Main Results and Discussion

Headspace SPME efficiently captured terpenes and light volatiles in cannabis samples, resolving key cannabinoids by retention time and accurate mass. Derivatization profiling uncovered sugars, amino acids and fatty acids in magic mushrooms and plant matrices with spectral library match factors exceeding 900. Synthetic cathinones in bath salts and alkaloids in khat were detected with mass accuracy below 1 ppm, enabling unambiguous formula assignments and structural elucidation. Complex botanical backgrounds did not compromise selectivity thanks to resolving power up to 50 000 and high‐resolution deconvolution.

Benefits and Practical Applications

The combined approach delivers

• Comprehensive discovery of known and novel compounds in forensic seizures.
• Fast library‐based screening and confident confirmation using accurate mass and fragmentation patterns.
• Quantitative profiling for regulatory and quality control contexts.
• Improved differentiation of isomeric substances and complex matrices.

Future Trends and Opportunities

Continued advances in high resolution mass spectrometry hardware and data processing algorithms will enable real‐time screening, expansion of spectral libraries with emerging synthetic analogues, and integration with orthogonal techniques such as ion mobility. Miniaturized sampling devices and enhanced automation will support field deployable forensic workflows and rapid response to novel psychoactive substances.

Conclusion

This study demonstrates that GC–HR-TOFMS, coupled with tailored sample preparation and high resolution deconvolution, provides a comprehensive solution for the analysis of complex forensic botanicals. The method achieves high confidence in identification, sensitive detection across wide concentration ranges, and adaptability to diverse sample types.

Reference

John Rorabeck, David E Alonso, Joe Binkley Characterization of Complex Forensic Samples by Gas Chromatography–High Resolution Time‐of‐Flight Mass Spectrometry Berrien County Forensic Laboratory and LECO Corporation 2017