Examining the effect of time by thin layer chromatography on ballpoint pen writings held in different conditions

Ink analysis has an important place in forensic document analysis. Among the ink analysis techniques which are divided into two as destructive and non-destructive, thin layer chromatography (TLC) is preferred because it is inexpensive, fast and less destructive. In this study, the similarities and differences of a total of thirty ballpoint pen inks (twelve blue, ten black and eight red) from different brands supplied from the market were revealed by making TLC profiles in the butanol:ethanol:water (9:1:1) solvent system at the first transfer to the paper. Then, the changes in the TLC profiles of the ink samples obtained from the documents kept in different conditions (room conditions, dark environment and sunny environment) for six months were determined on a monthly basis in the selected solvent system. For this purpose, ink samples extracted from paper with methanol were applied to silica gel plates and carried out in the selected solvent system. Silica gel plates were examined under the naked eye and UV light, and the Rf values of each spot were calculated and recorded. As a result, inks with very different TLC profiles were observed, as well as identical TLC profiles in each ballpoint pen group. While six groups with similar TLC profiles were formed in blue ballpoint pens, two groups were formed in black ballpoint pens and two different pens were separated from the others and behaved completely uniquely. Among the red ballpoint pens, four pens can be completely differentiated from the others as a result of the change in the TLC profile over time, while the other pens have formed two groups among themselves. Using these observations, it has been seen that a preliminary classification can be made according to the TLC profiles in a fast and practical way before further analysis.