Forensic Perspectives on Gas Chromatography

Gas chromatography (GC) techniques are increasingly central to forensic chemical analysis.

In this article, we draw on insights from three researchers whose work illustrates the advances being made: Petr Vozka (California State University, Los Angeles), who investigates time-dependent chemical changes in latent fingerprints using comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC–TOF-MS); Ira Lurie (George Washington University), whose research explores flip-flop chromatography and GC–vacuum ultraviolet spectroscopy (VUV) for drug isomer resolution; and Darshil Patel (University of Windsor), who examines VOC transitions from life to death via GC×GC–TOF-MS. Each researcher contributes specific methodological innovations, challenges, and forensic implications.

Fingerprint Aging Using GCxGC–TOF-MS

Vozka’s work focuses on how latent fingerprint residues evolve chemically over time, and how GC×GC–TOF-MS can detect these changes with high resolution. He explains that fingerprint composition undergoes evaporation of volatilessoon after deposition, followed by oxidative degradation of lipids, leading to the formation of new oxygenated species and high-molecular-weight residues. 

Using the two-dimensional separation of GC×GC, combined with time-of-flight MS, Vozka’s group aims to resolve closely overlapping degradation pathways and minor compounds that one-dimensional GC might miss. He notes that “GC×GC–TOF-MS offers unparalleled resolution and sensitivity, allowing us to monitor subtle chemical transformations that occur as fingerprint residues age.”

Vozka suggests that integrating chemometric modelling to interpret high-dimensional data sets allows the construction of predictive aging models, “which is instrumental in building reliable and predictive forensic models.”

He acknowledges challenges such as sampling variability, surface interactions, environmental influences, and the need to control sample preparation. He also describes the use of compound ratios to minimize sensitivity to absolute amounts.

In practical forensic settings, Vozka envisions these models augmenting standard fingerprint analysis rather than replacing it: the chemical age estimate provides contextual timing information for investigators, helping support or refute timelines.

The advantages of GCxGC–TOF-MS for forensic analysis of fingerprints include increased peak capacity, better separation of minor degradation species, and richer data sets for multivariate analysis. Despite this, the technique necessitates quality assurance, specialized skill sets, and is hindered by the limited availability of fully curated libraries for fingerprint constituents.

Flip-Flop Chromatography and GC–VUV in Drug Isomer Analysis

Lurie’s research addresses a different but complementary forensic challenge: distinguishing drug isomers, especially novel psychoactive substances, with enhanced specificity. Lurie reports on the use of flip-flop chromatography, employing silica hydride stationary phases to alternate between reversed-phase and aqueous normal-phase modes, enabling orthogonal separations without changing solvents (1). By switching modes, complementary separation behavior is achieved quickly, reducing the need for dual-column systems. Lurie reports run-to-run repeatability ≤ 0.6%.

Lurie also integrates GC–vacuum ultraviolet (VUV) spectroscopy to gain additional spectral discrimination (2). He describes how second-derivative processing of VUV absorbance curves can distinguish positional isomers by revealing minima, maxima, and saddle points unique to each structure. In his work, 14 of 15 JWH-018 positional isomers were distinguished via spectral library matching, surpassing typical PCA-based approaches on first derivatives. 

One asserted advantage is that coeluting peaks can be deconvoluted via Beer–Lambert modeling of VUV spectra, whereas EI-MS often requires complex chemometrics to separate overlapping fragments. Lurie also notes that GC–VUV offers improved discrimination of positional isomers that EI-MS may struggle with. He considers the approach feasible for forensic labs, especially with existing liquid chromatography (LC) hardware that can be adapted to flip-flop chromatography.

Lurie emphasizes the forensic importance of accurate isomer identification: “Misidentification could lead to a defendant being charged erroneously for possession or sale of a controlled substance.”

VOC Profiling and Decomposition: From Life to Death

Patel’s research explores the trajectory of volatile organic compounds (VOCs) released before and after death, with the goal of clarifying chemical signatures over time (3). He applies GC×GC–TOF-MS to capture the evolving VOC odor landscape. This configuration significantly improves selectivity, sensitivity, and—most importantly—peak capacity, yielding a much more detailed and representative chemical fingerprint of the decomposition odor profile than standard GC–MS can provide.

Patel describes the VOC evolution from ante-mortem and post-mortem “as a continuum … no single compound serves as a universal marker.” In the early stages of post-mortem, nitrogen-containing compounds derived from amino acid breakdown dominate. In later stages, sulfur-containing volatiles and other degradation products increase, driven by microbial metabolism and tissue decomposition. Environmental factors—temperature, sunlight, humidity, and ozone—modulate how these VOCs persist or alter.

One applied consideration is search-and-rescue (SAR) and human remains detection (HRD) dogs. Because VOC composition can shift markedly within the first 96 hours, Patel suggests deploying SAR and HRD dogs concurrently during this window to maximize detection likelihood.

Methodological constraints include variable VOC recovery depending on containment (bags, shrouds, hoods) and lack of data therein, and decomposition advancing at different rates depending on the body part. Patel recommends replicating studies across environmental conditions and seasons to improve generalizability.

Shared Challenges and Considerations

Although the three research avenues differ in target analytes, they share common technical and interpretative challenges:

• Complex matrices and trace levels: Forensic samples often contain many compounds at low concentrations, requiring high sensitivity and orthogonal separation.
• Coelution and deconvolution: Even with GC×GC or dual-mode strategies, overlapping peaks may require chemometric, spectral-fitting, or derivative-based approaches.
• Variability and environmental effects: Ambient conditions, surface interactions, sample collection protocols, and contaminant adsorption introduce variability.
• Standardization and validation: Building reference libraries (spectral, chromatographic), inter-lab reproducibility, calibration, and method validation are essential before routine forensic adoption.
• Interpretative frameworks: Multivariate or machine-learning modeling may help translate rich chemical data into forensic conclusions, but overfitting, bias, and model defensibility must be guarded against.
• Legal admissibility: Forensic methods must meet standards for error rates, transparency, repeatability, and expert defensibility in court.

Each researcher emphasizes the importance of robust sample handling, controlled protocols, and cross-validation of chemical models to ensure that findings are reliable, reproducible, and legally defensible.

Future Outlooks

Vozka envisions fingerprint aging models being built to align with standard sampling protocols, allowing forensic labs to leverage chemical timing insight without disrupting established procedures. While Lurie stressed complementarity, Patel called for replication in a range of environments, both pragmatic paths forward.

Their research illustrates the application of advanced GC techniques in forensic science:

Fingerprint aging via GC×GC–TOF‑MS provides chemical timing information.

Flip-flop chromatography and GC–VUV improve the specificity and efficiency of forensic drug analysis.

VOC profiling with GC×GC–TOF‑MS tracks decomposition chemistry and informs detection strategies.

Each approach requires careful sample handling, reproducibility, and data interpretation within forensic contexts. While challenges remain, these studies demonstrate how GC methods can support forensic investigations.

For an extended interview with Petr Vozka, please click here.

For an extended interview with Ira Lurie, please click here.

For an extended interview with Darshil Patel, please click here.

References

(1) Appia-Kusi, V.; Lurie, I. S. Utility of “Flip-flop” Chromatography Employing Silica Hydride Stationary Phases with Simultaneous Photodiode Array Ultraviolet and Single Quadrupole Mass Detection for the Analysis of Seized Drugs. J. Chromatogr. A 2023, 1707, 464294. DOI: 10.1016/j.chroma.2023.464294

(2) Dombrowski, A.; Le, D.; Lurie, I. S. GC-VUV Spectroscopy of Synthetic Cannabinoid Isomers, Diastereomers and Homologs: Increasing Differentiation by Derivative Spectral Processing. Forensic Chem. 2025, 42, 100635. DOI: 10.1016/j.forc.2024.100635

(3) Patel, D.; Burr, W. S.; Daoust, B. et al. Identifying the Transition from Ante-Mortem to Post-Mortem Odor in Cadavers in an Outdoor Environment. Forensic Sci. Int. Synerg. 2025, 11, 100616. DOI: 10.1016/j.fsisyn.2025.100616