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Infrared Spectrometry in Discriminant Analysis of Laser Printer and Photocopy Toner on Questioned Documents

Abstract Differentiating between black powder toners used in laser printers and copiers can be challenging for forensic examiners. One hundred and eight samples from different types of cartridges produced by 10 manufacturers were studied 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. The FTIR spectra were classified into 15 groups. This classification served as a basis for the development of an analytical scheme for differentiating black powder toners. Obtained spectra and all the available information could be used to create a database. The results obtained confirm the multiplicity and compatibility of toners.