Laser-induced breakdown spectroscopy and chemometric analysis of black toners for forensic applications

In the present work, laser-induced breakdown spectroscopy (LIBS) was used to differentiate between different black toners of printers and photocopiers based on their elemental composition. Measurements were performed on 23 toner samples of different printers and six different photocopiers (of different brands and models). The LIBS spectra were compared to characterize each toner type. Multivariate statistical analysis based on PCA and graph clustering was used to develop a discrimination model between the toners in questioned documents. Good discrimination of both brand and model toners was obtained. The results may be beneficial for forensic applications in the investigations of questioned documents.