HPLC analysis of black ballpoint pen ink exposed to different light conditions

The light conditions to which a document is exposed are often unknown to the forensic scientist. It has been shown that the dyes in ink can degrade when exposed to light which can cause the relative abundance of dye components to change. This might cause an analyst to determine that two ink samples, one exposed and one not exposed to light, are from different sources when they were not. Though dye components in two ink samples from the same source may differ qualitatively, it has been shown that the rate at which they degrade is similar. Controlled light exposure to induce degradation and the subsequent comparison of degradation rates has been shown to be an effective method in comparing inks from blue ballpoint pens that have undergone different light conditions.;High-performance liquid chromatography was used to analyze thirty-two black ballpoint pens that were exposed to fluorescent light. The relative abundance of dye components was then plotted on a ternary diagram. Black ballpoint pen inks containing crystal violet dye degraded in the same manner as blue ballpoint pen inks containing the same dye. The method of controlled light exposure to induce the degradation of the dye components in black ballpoint pens was tested in two blind case studies containing a total of twenty ink sample pairs. The analyst was able to correctly conclude whether or not the ink samples could have come from the same pen for sixteen of the ink sample pairs.