Forensic Analysis of Black, Blue, Red, and Green Ballpoint Pen Inks

Abstract

Ballpoint pen inks (24 black, 18 blue, 21 red and 15 green) purchased in Mauritius were analyzed by 5 different methods, namely thin layer chromatography (TLC ), Fourier transform infrared (FTIR ), visible spectroscopy (VIS ), filtered light examination (FLE ) and Raman spectroscopy (Raman ). The results of the different colored ballpoint pen inks obtained by the above techniques were compared in terms of their discriminating power (D.P.). The results showed that the non-destructive technique FLE was found to be the one with the highest D.P. (0.94–0.99) for the black, red and green ballpoint pen inks whereas for the blue ballpoint pen inks , highest D.P. was achieved using TLC . Higher D.P. were obtained for red, green, black and blue ballpoint inks by FLE and TLC compared to the other methods such as VIS , FTIR and Raman , showing the lower effectiveness of the latter for ink analysis. Improvement in discrimination could be obtained by combining different methods of analysis. Hence, by applying FLE , TLC and FTIR spectroscopy , all the 24 black ballpoint pen inks were successfully discriminated, whilst for the blue ballpoint pen inks , the combination of two methods (FLE and TLC ) resulted in a discriminating power of 0.99. Only one pair of pens from the same brand/manufacturer Cello could not be discriminated. On the other hand, the study has also shown that by combining FLE with TLC , all the 21 red and 15 green ballpoint pen inks were successfully discriminated, except for two pairs of red pens and one pair of green pens.