Statistical Discrimination of Blue Ballpoint Pen Inks by Infrared (IR) Spectroscopy


  • Mohamed Izzharif Abdul Halim
  • Nur Syafinaz Abdul Aziz
  • Norashikin Saim
  • Rozita Osman
  • Halila Jasmani



Blue ballpoint pen inks, PCA, AHC, FTIR,


Statistical chemometric method was used in discriminating 24 blue ballpoint pen inks from six different brands (Pilot, Carera, Stabilo, Faber-Castle, G-soft and Papermate) available in Malaysian market. Discrimination method was developed based on the combination of infrared spectra (IR) and chemometric technique which comprise of principal component analysis (PCA) and Agglomerative Hierarchical Clustering (AHC). The chemometric software used was XLSTAT 2011. The spectral region 4000–400 cm-1 was used to ‘fingerprint’ each ink from the 24 samples. PCA was used to detect any outliers whereas AHC was used to separate the ballpoint pen inks into their own class. This study showed that acceptable statistical discrimination (70.92% correct classification of the ballpoint pen dataset) between these 24 samples. FTIR-PCA and FTIR-AHC were successfully discriminate three different brands which were Carera, Pilot and g-soft. While, the other three brands, Papermate, Fabercastle and Stabilo could not be discriminated perfectly. The results of this study indicate that Transmission FTIR Spectroscopy coupled with chemometrics is useful discriminating tool for forensic studies involving inks.


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