Characterization and sequence determination of pen inks, red sealing inks, and laser toners by TOF-SIMS and ATR FTIR

Abstract

Document authentication is one of the most important fields in forensic science and includes analysis of handwriting, seal imprint, and printed materials. In this study, we investigated intersection lines by pen inks, red stamping ink, and laser toner using time-of-flight secondary ion mass spectrometry (TOF-SIMS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR FTIR). TOF-SIMS is very useful when the quantity of the sample is insufficient or the sample is very precious. Each ink showed specific ion peaks from inorganic species such as Al, Si, Ti, Cr, Mn, Fe, Zn, and Pb and from organic components at a mass range of m/z 200-450 in TOF-SIMS spectra. ATR FTIR results also revealed different spectra for ink and toner samples. The overlapped area of ballpoint pen writing, red sealing stamping, and laser printing in a document was investigated in order to identify the sequence of recording. The sequence relations for various cases were studied from TOF-SIMS mapping image and ATR FTIR spectra. This study indicated that TOF-SIMS and ATR FTIR are useful techniques to determine the sequence of writing and printing under question. Copyright (c) 2014 John Wiley & Sons, Ltd.