Identification of laser-printed ink marks based on characteristic VOC fingerprints and isomer discrimination via HS-GC-IMS combined with multivariate statistical analysis

[Display omitted] •The HS-GC-IMS method was first applied to examine laser-printed documents.•Multivariate statistical models accurately distinguish and classify ink marks.•Trace VOCs in ink marks can be detected in situ without any pretreatment.•Visual and digital expression contributed to precise identification of typescripts.•The aliphatic isomers in the samples were identified using reduced mobility values. Examination and analysis of ink marks printed by laser printers are of significant importance in both criminal investigation and forensic expertise. In this paper, a novel method, headspace gas chromatography-ion migration spectrometry (HS-GC-IMS), combined with multivariate statistical analysis, has been developed for the identification of laser-printed ink marks. Ninety-six volatile organic compounds (VOCs), potentially originating from residual volatile compounds in paper preparation and toner transfer, were detected in five typescripts containing different toners and blank paper. Among all the detected VOCs, aldehydes exhibited the highest concentration. Visual identification was conducted through fingerprint analysis, clearly revealing the distinctive markers of all the samples. Aliphatic isomers were effectively discriminated in this analytical system. After eliminating the paper background, five printed ink marks were efficiently classified using principal component analysis (PCA), orthogonal partial least squares discrimination analysis (OPLS-DA), heatmap analysis, and hierarchical cluster analysis (HCA). These findings provide a feasible new idea for identifying, classifying, and tracing the sources of different types of printed ink marks via trace and non-destructive detection and visual analysis.