Volume 42, Issue 6 (November 1997)
Separation and Comparison of Fountain Pen Inks by Capillary Zone Electrophoresis
The analysis of inks as part of the detection of fraudulent documents is a small but important part in the operation of a forensic laboratory. Apart from optical methods, multiple thin layer chromatography (TLC) is used to separate, compare and distinguish inks based on their dye composition.
Capillary electrophoresis (CE), a relatively young separation technique with very high resolution power, was used for the analysis of water soluble fountain pen inks. Inks are complex mixtures of synthetic organic and inorganic dyes, surfactants, resins and other components. The study focused on the optimization of the separation of 10% aqueous solutions of commercially available inks with respect to resolution and analysis time. During the method development process different buffers, organic modifiers and surfactants were tested. Good results were obtained with a 100 mM borate buffer at pH 8.0 containing 20% methanol. The separations were reproducible and led to baseline resolution of almost all components of blue and black fountain pen inks. Electropherograms of 15 inks of various manufacturers and countries of origin showed patterns which were in the most cases distinctly different from each other. Initial studies of the separation of extracts of inks from paper were successful and are reported here as well. Therefore, it was concluded that CE is a powerful tool for the identification of water soluble writing inks.