Problems of Forensic Sciences 2001 Vol. 46 (XLVI) 383-400
DIFFERENTIATION OF BALLPOINT AND LIQUID INKS – A COMPARISON OF METHODS IN USE
Ewa FABIAŃSKA, Beata M. TRZCIŃSKA
Institute of Forensic Research, Cracow, Poland
Streszczenie
The differentiation and identification of inks is a problem often encountered by experts in the examination of documents. There are two methods generally used to this aim: non-destructive – observation in visible light and infrared, and destructive method – thin layer chromatography (TLC). Infrared spectroscopy is also used, in conjunction with a microscope (MK-FTIR). This method is applied more rarely, as it gives worse results in the examination of ink samples taken from paper than in the analysis of pure ballpoint pen inks. It also demands a substantially larger amount of ink than TLC. Technological advances, in turn, have facilitated a rediscovery of Raman spectroscopy as a non-destructive method, used in the examination of writing lines among other things. The aim of the tests conducted was to rate the usefulness of the four above-mentioned methods in cases of ink differentiation, which raise doubts. The subject of the tests was black and blue ballpoint pen inks and liquid inks, that are in common use. Using optical methods and Raman spectroscopy, a line of writing applied to paper was analysed; for thin-layer chromatography, the ink was extracted from the paper while in the case of infrared spectroscopy , it was taken directly from the writing instrument. The achieved results were analysed primarily assuming the possibility of distinguishing samples in VSC-1. In the case of inks which were indistinguishable or difficult to distinguish, the Raman spectrum was analysed, as were the chromatograms, and in the final phase, the infrared spectrum as well. It was found that the Raman spectroscopy method could serve as a supplement to the optical method. However, the destructive methods cannot be completely disregarded.
Słowa kluczowe
Ink; VSC-1; Raman spectroscopy; TLC; FTIR.