Characterization of ballpoint pen inks by ATR FT-IR microspectrocopy

A homemade slide-on Ge µIRE for ATR FT-IR spectral acquisition with an infrared microscope is employed for ballpoint pen inks characterization. Due to the small sampling area of the IRE, a trace of written ink on a paper can be analyzed. Direct correlation between the molecular information and their infrared absorption enable the identification of inks. Since inks have their own unique formula depending on manufacturer recipe, their spectra demonstrate their unique characteristic. Although the spectra of ink written on paper have interference from paper, the wavenumber region which display unique ink characteristic can be identified and employed for the ink identification. Moreover, a line-crossing of ink which is forged with other pen inks is investigated by linear point-by-point measurement. The operations are non-destructive and can be performed without an additional sample preparation. The technique suitable for document examination in as well as other forensic evidences based on unique chemical signature of ink.