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Fingermark residue consists of traces of sweat and oil left behind when a person touches a solid surface. These forensic traces have been shown to distinguish class characteristics between fingermark donors such as sex and relative age. Traces of fingermark residue with anthropogenic contamination have been studied to demonstrate the feasibility and usefulness of this type of forensic evidence within legal proceedings. A novel nontargeted method for analyzing fingermark residue was developed and optimized using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry detection (GC×GC-TOFMS). Method optimization was performed experimentally for six parameters using a Pegasus BT 4D GC×GC-TOFMS with dual-stage cryogenic, thermal modulation. Two sample extraction methods consisting of pipette agitation and cotton swab extraction were compared and evaluated for optimal fingermark residue extraction from deposited marks. Recovery of fingermark residue was found to be between 10% and 86% for five analytes, and suggestions for improvement of the sample extraction method were given. Amount of deposited residue was evaluated to inform more realistic forensic evidence scenarios. Single fingermark depositions were found to provide significantly less residue but were above detectable limits of the method.
Greener and sustainable chemistry principles were considered for optimized methods. The previously optimized helium carrier gas method was translated to three possible methods using hydrogen carrier gas to transition away from fossil fuel-derived resources. The chosen hydrogen carrier gas method reduced chromatographic run time by half, doubled sample throughput within one hour, and increased the sustainable nature of otherwise energy-intensive advanced chromatographic and mass spectrometric techniques. Green chemistry metrics found alternative solvents used in sample preparation to be greener than dichloromethane, which was banned in nonessential manufacturing, distribution, and research applications in 2024. Green chemistry metrics were applied to compare 1D GC and GC×GC methods as well but low variation between metric criteria led to similar metric scores.
Anthropogenic contamination of fingermark residue was applied to cosmetic and gunshot residue applications. Cosmetic contamination has been shown to inform lifestyle choices of fingermark donors. Three sunscreen and two moisturizing substances were successfully resolved from endogenous fingermark residue for donor differentiation. A proof-of-concept study for identification of organic components of gunshot residue successfully identified four phthalates related to explosives, two of which are targeted using the Organization of Scientific Area Committees (OSAC) for Forensic Science standardized method for collection and analysis of gunshot residue. The nontargeted method developed previously in this work enabled successful resolution and relative quantitation of anthropogenic compounds in fingermark residue and provide foundation for future forensic work in this application.
