Nontargeted Screening of Fingermark Residue Using Comprehensive Two-Dimensional Gas Chromatography–Time-of-Flight Mass Spectrometry for Future Use in Forensic Applications

Fingerprints are routinely used as evidence in forensic investigations. Fingermarks, any mark left by a donor whether a complete print or not, include sweat and oil excreted by the donor. The chemical components of fingermarks are typically analyzed by gas chromatography-mass spectrometry (GC-MS). Complexity from the number of endogenous and exogenous components associated with fingermarks tends to cause challenging coelutions in resulting chromatograms. In these scenarios, nontargeted analysis can provide substantial benefits over traditional targeted methods that exist in the literature. In this proof-of-concept study, a nontargeted method for analyzing fingermarks was developed and optimized using comprehensive two-dimensional gas chromatography (GC×GC-TOFMS). Two different methods for extracting fingermarks off a microscope slide were evaluated for reproducibility and the quantity of extracted analytes, and a cotton swab collection with solvent extraction was chosen. Instrumental parameters were experimentally optimized to produce a final workflow. The optimized extraction and instrument methods together identified 70 fingermark analytes. Exogenous components within the deposited residue were resolved from endogenous fingermark compounds and used to differentiate donors based on personal care products used by the donor. The extra chromatographic space from GC×GC-TOFMS analysis was beneficial for resolving cosmetic compounds from endogenous fingermark compounds, some of which have been shown to coelute in GC-MS studies previously. The potential for a nontargeted screening of fingermarks for exogenous compounds in a forensic setting is demonstrated as an analysis of trace evidence.