Forensic discrimination of photocopy and printer toners. III. Multivariate statistics applied to scanning electron microscopy and pyrolysis gas chromatography/mass spectrometry

Abstract

Copy toner samples were analyzed using scanning electron microscopy with X-ray dispersive analysis (SEM-EDX) and pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). Principal component and cluster analysis of SEM data for 166 copy toner samples established 13 statistically different subgroups, with the presence or absence of a ferrite base being a major division. When toners were compared for which both SEM and reflection-absorption infrared spectral data were available, 41% of the samples could be assigned to specific manufacturers. Py-GC/MS on poly(styrene:acrylate)-based toners produced eight peaks relevant to toner differentiation. One third of the toners clustered in a small group that contained five statistically different subgroups. Of the 57 toners for which both Py-GC/MS and SEM data were available, 31 could be differentiated using the combined analytical results. The synergy of the complementary information provided by Py-GC/MS and SEM narrows matching possibilities for forensic investigations involving copied or laser printed documents.

Forensic discrimination of photocopy and printer toners II. Discriminant analysis applied to infrared reflection-absorption spectroscopy

“…This work has demonstrated the statistical validity of the groups of toner spectra assigned by previous work at the FBI Laboratory [22]. Further work in our laboratories involves comparisons of the discrimination achieved by R-A IR to that achieved using copy toner elemental compositions determined by scanning electron with X-ray dispersive analysis (SEM-EDX) and organic polymer composition analyzed by Py-GC/MS [42]. …”

Forensic application of ESEM and XRF-EDS techniques to a fatal case of sodium phosphate enema intoxication

“…ESEM and confocal electron microscopy methods have already been used in soil and gunshot residues analysis [17][18][19], in questioned document examination [20], in dental comparison [21], in the diagnosis of work-related pulmonary diseases [22], and in cutting and shooting crime investigation [23,24] demonstrating them to be powerful diagnostic tools that can sometimes provide strong forensic evidence.…”

XPS investigations of ink‐jet printed paper

“…In the case of laser printers and photocopier toners this can be achieved, e.g., by the combination of scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis with Fourier-transform infrared spectroscopy (FTIS) 16 and/or gas chromatography. 17 The toner usually contains iron oxide with additional characteristic elements that may vary systematically with the manufacturing origin. These elements can easily be detected using an EDX analysis.…”