Raman spectroscopy of ballpoint-pen inks using chemometric techniques

Abstract

The Raman spectroscopic technique has been shown to possess good abilities to analyse ballpoint-pen inks. This in situ technique involves directing light onto ballpoint-pen ink samples to generate Raman spectrum, providing ‘molecular fingerprints’ of the ink samples allowing comparison by direct visual comparison. In this study, 30 ballpoint-pen inks of two different colours, i.e. blue and red of five different brands, i.e. Pilot, Stabilo Kilometrico, G-Soft and Faber Castell, were analysed using a Raman spectrometer with the objective of establishing distinctive groupings according to brand. The resultant spectra were first compared and grouped manually. Due to the similarities in terms of colour and shade of the ballpoint-pen ink samples, distinctive groupings cannot be achieved by means of direct visual comparison; however, this was not the case for Principal Component Analysis (PCA). The PCA displays (by means of its score plot) distinctive groupings of the ballpoint-pen inks. The results of this study demonstrate that PCA can be used to objectively interrogate ballpoint-pen inks of similar colour and, more importantly, of different brands.