Forensic discrimination of photocopy and printer toners. III. Multivariate statistics applied to scanning electron microscopy and pyrolysis gas chromatography/mass spectrometry.
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.
Egan
William J
WJ
Department of Chemistry and Biochemistry, The University of South Carolina, Columbia, SC 29208, USA.
Galipo
Randolph C
RC
Kochanowski
Brian K
BK
Morgan
Stephen L
SL
Bartick
Edward G
EG
Miller
Mark L
ML
Ward
Dennis C
DC
Mothershead
Robert F
RF