Application of CE-MS to examination of black inkjet printing inks for forensic purposes

The potential of capillary electrophoresis coupled to mass spectrometry with electrospray ion source and time of flight analyser (CE-ESI-TOF-MS) in the analysis of inkjet inks was investigated. The developed and validated method allowed reliable and repeatable analysis of black inkjet inks extracted from printouts. Over a dozen inkjet printouts printed on various printer models from different manufacturers were analysed under selected conditions to determine the variation of chemical composition of inks between different brands and types. It was ascertained that the developed method is capable of revealing qualitative differences between ink samples. For most of the investigated inks, the studies showed the presence of a characteristic mass spectrum originating from the surfactant or polymer. The mass distribution of the additive is distinctive for some inkjet ink producers, and allows for group identification of inks. The results showed the strength of the CE-ESI-TOF-MS method as an effective technique for forensic purposes, requiring a small amount of inkjet ink samples and giving analytical information that is useful in the identification of compounds.