Abstract
Copy toner samples were analyzed using reflection-absorption infrared microscopy (R-A IR). The grouping of copy toners into distinguishable classes achieved by visual comparison and computer-assisted spectral matching was compared to that achieved by multivariate discriminant analysis. For a data set containing spectra of 430 copy toners, 90% (388/430) of the spectra were initially correctly grouped into the classifications previously established by spectral matching. Three groups of samples that did not classify well contained too few samples to allow reliable classification. Samples from two other pairs of groups were similar and often misclassified. Closer examination of spectra from these groups revealed discriminating features that could be used in separate discriminant analyses to improve classification. For one pair of groups, the classification accuracy improved to 91% (81/89) and 97% (28/29), for the two groups, respectively. The other pair of groups were completely distinguishable from one another. With these additional tests, multivariate discriminant analysis correctly classified 96% of the 430 R-A IR toner spectra into the toner groups found previously by spectral matching.
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Acknowledgements
This work was funded by the FBI Academy and by award number 97-LB-VX-0006 from the Office of Justice Programs, National Institute of Justice, Department of Justice. Points of view in this document are those of the authors and do not necessarily represent the official position of the US Department of Justice. Portions of this work were presented at Pittcon '97 (Atlanta, GA, 18 March 1997), at FACSS '97 (Providence, RI, 27–31 October, 1997), and at the American Academy of Forensic Sciences Meeting (San Francisco, CA, 12 February 1998).
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This is publication number 03–03 of the Laboratory Division of the Federal Bureau of Investigation. Names of commercial manufacturers are provided for identification only, and inclusion does not imply endorsement by the Federal Bureau of Investigation.
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Egan, W.J., Morgan, S.L., Bartick, E.G. et al. Forensic discrimination of photocopy and printer toners II. Discriminant analysis applied to infrared reflection-absorption spectroscopy. Anal Bioanal Chem 376, 1279–1285 (2003). https://doi.org/10.1007/s00216-003-2074-z
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DOI: https://doi.org/10.1007/s00216-003-2074-z