Forensic classification of ballpoint pen inks using high performance liquid chromatography and infrared spectroscopy with principal components

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Journal Article
Vibrational Spectroscopy, 2006, 40 (2), pp. 270 - 277
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Several varieties of blue ballpoint pen inks were analysed by higher performance liquid chromatography (HPLC) and infrared spectroscopy (IR). The chromatographic data extracted at four wavelengths (254, 279, 370 and 400 nm)was analysed individually and at a combination of these wavelengths by the soft independent modeling of class analogies (SIMCA) technique using principal components analysis (PCA) to estimate the separation between pen samples. Linear discriminant analysis (LDA) measured the probability with which an observation could be assigned to a pen class. The best resolution was obtained by HPLC using data from all four wavelengths together, differentiating 96.4% pen pairs successfully using PCA and 97.9% pen samples by LDA> PCA separated 60.7% of the pen pairs and LDA provided a correct classification of 62.5% of the pends compared to IR. The need to develop a suitable IR method for analysing nlue ball-point pen inks has been emphasised and it is hoped that the development of such a method would indeed providea valuable tool for the non-destrictive analysis of blue ball-point pen ink samples for forensic purposes.
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