Direct Analysis of Basic Dyes and Photodegradation Products in Blue Ballpoint Inks via Desorption Electrospray Ionization Mass Spectrometry

Abstract

Desorption electrospray ionization mass spectrometry (DESI-MS) is a useful ambient ionization technique for ink analysis, offering rapid characterization of dyes with minimal sample destruction─a critical requirement for forensic evidence. While DESI-MS preserves samples in their native state, its utility in monitoring ink degradation during accelerated weathering has remained largely unexplored. In this study, written samples from six blue ballpoint pens were subjected to accelerated weathering using the AATCC TM169-2025 to simulate exposure to semitropical and semiarid outdoor climates and were analyzed via DESI-MS. Five primary dyes─Basic Violet 1, 3, and 4 and Basic Blue 7 and 26─were identified along with their respective photodegradation products. The results demonstrate that most dyes follow a linear degradation trend over time, establishing DESI-MS as a viable tool for the temporal profiling of questioned documents.