Fourier Transform Infrared (FTIR) Spectroscopy with Chemometric Techniques for the Classification of Ballpoint Pen Inks

Muhammad Naeim Mohamad Asri, Wan Nur Syuhaila Mat Desa, Dzulkiflee Ismail


FTIR spectroscopic techniques have been shown to possess good abilities to analyse ballpoint pen inks. These in-situ techniques involve directing light onto ballpoint ink samples to generate an FTIR spectrum, providing “molecular fingerprints” of the ink samples thus allowing comparison by direct visual comparison. In this study, ink from blue (n=15) and red (n=15) ballpoint pens of five different brands: Kilometrico®, G-Soft®, Stabilo®, Pilot® and Faber Castell® was analysed using the FTIR technique with the objective of establishing a distinctive differentiation according to the brand. The resulting spectra were first compared and grouped manually. Due to the similarities in terms of colour and shade of the inks, distinctive differentiation could not be achieved by means of direct visual comparison. However, when the same spectral data was analysed by Principal Component Analysis (PCA) software, distinctive grouping of the ballpoint pen inks was achieved. Our results demonstrate that PCA can be used objectively to investigate ballpoint pen inks of similar colour and more importantly of different brands.


Forensic Science, Principal Component Analysis (PCA), FTIR spectroscopy, Ballpoint pen inks, Direct Visual Comparison

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