The Analysis of Ballpoint Inks with APCI-MS after Fading with Light, Hydrogen Peroxide and Sodium Hypochlorite Bleach

Abstract

The ability to discriminate between different inks and to determine the length of time an ink has been on a substrate can provide important scientific evidence, especially in cases involving document fraud. Many techniques have been used to analyse inks for ink dating including chromatography and spectroscopy, but the results are unreliable as a result of factors affecting the aging process such as light. This study utilises established techniques in Forensic Document Examination, including filtered light examination but also novel techniques for ink analysis; Atmospheric Pressure Chemical Ionisation (APCI) to analyse inks and dyes with the aim of discriminating between samples based on their degradation products. APCI-MS was used for the first time to study nineteen ballpoint pens from a range of manufacturers by investigating the chemical processes that occur and the products that are formed following the deposition of ink onto a substrate and in solution. Monitoring the degradation process as an ink ages and fades enables the identification of components present in the inks. Using molecular mass data, accurate ink component identifications could be made over a period of two years on samples subjected to a range of external influences. Light, hydrogen peroxide and sodium hypochlorite bleach were used to simulate natural and deliberate fading of inks and dye solutions. Benzophenone and phenol molecules were identified as degradation products but their presence differed for each of the different conditions tested such as no phenol products when bleach was used. This novel approach to ink analysis utilises existing equipment commonly used by document examiner to analyse inks that are old or faded in some way, in order to discriminate between the inks or determine method of alteration