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 laborator y. 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 separ ation technique with very high resolution power, was used for the anal ysis of water soluble fountain pen inks. Inks are complex mixtures of synthetic organic and inorganic dyes, surfactants, resins and other co mponents. The study focused on the optimization of the separation of 1 0% aqueous solutions of commercially available inks with respect to re solution and analysis time. During the method development process diff erent buffers, organic modifiers and surfactants were tested. Good res ults were obtained with a 100 mM berate buffer at pH 8.0 containing 20 % methanol. The separations were reproducible and led to baseline reso lution of almost all components of blue and black fountain pen inks. E lectropherograms of 15 inks of various manufacturers and countries of origin showed patterns which were in the most cases distinctly differe nt from each other. Initial studies of the separation of extracts of i nks from paper were successful and are reported here as well. Therefor e, it was concluded that CE is a powerful tool for the identification of water soluble writing inks.