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

• Published in: Analytical and bioanalytical chemistry 2003-08, Vol.376 (8), p.1286-1297
• Main Authors: Egan, William J, Galipo, Randolph C, Kochanowski, Brian K, Morgan, Stephen L, Bartick, Edward G, Miller, Mark L, Ward, Dennis C, Mothershead, 2nd, Robert F
• Format: Article
• Language: English
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-003-2099-3

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.