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Characterization and Dating of Blue Ballpoint Pen Inks Using Principal Component Analysis of UV–Vis Absorption Spectra, IR Spectroscopy, and HPTLC


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Samir A. Senior, Ph.D.
Department of Chemistry, Faculty of Science
Alexandria University


Abstract:  The ink of pens and ink extracted from lines on white photocopier paper of 10 blue ballpoint pens were subjected to ultraviolet–visible (UV–Vis) spectroscopy, infrared (IR), and high-performance thin-layer liquid chromatography (HPTLC). The Rf values and color tones of the bands separated by thin-layer chromatography (TLC) analysis used to classify the writing inks into three groups. The principal component analysis (PCA) investigates the pen responsible for a piece of writing, and how time affects spectroscopy of written ink. PCA can differentiate between pen ink and ink line indicates the influence of solvent extraction process on the results. The PCA loadings are useful in individualization of a questioned ink from a database. The PCA of ink lines extracted at different times can be used to estimate the time at which a questioned document was written. The results proved that the UV–Vis spectra are effective tool to separate blue ballpoint pen ink in most cases rather than IR and HPTLC.