The analysis of fountain pen inks by capillary electrophoresis with ultraviolet/visible absorbance and laser‐induced fluorescence detection

Abstract

Information on the identity of inks adds to the circumstantial evidence in legal cases involving fraudulent documents. In combination with optical methods, multiple thin-layer chromatography (TLC) is currently the analytical tool used by forensic chemists to separate, compare and distinguish inks based on their dye composition. In our studies, capillary electrophoresis (CE) 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 investigations included the development of an electrophoretic separation method, the optimization of an extraction procedure for inks from paper as well as the evaluation of ultraviolet/visible (UV/VIS) absorbance and laser-induced fluorescence (LIF) detection for the analysis of inks by CE. Good results for the separation of 17 blue and black inks of different manufacturers and countries of origin were obtained with 100 mM borate buffer, pH 8.0, containing 20% methanol. The electropherograms of the inks and their extracts from paper showed patterns that were in most cases distinctly different from each other. Ultraviolet/visible scans can be used to compare spectra of the separated main and trace components of inks. Fluorescence detection at different excitation and emission wavelengths was more sensitive, but added to the complexity of the electropherograms due to the excitation of coextracted fluorescing paper components. The resolution power of CE combined with the information content provided by the detection modes investigated prove CE to be a powerful tool for the identification of water-soluble inks used on paper documents.

Characterization and Dating of Blue Ballpoint Pen Inks Using Principal Component Analysis of UV–Vis Absorption Spectra, IR Spectroscopy, and HPTLC

“…A set of 10 blue ballpoint pens were purchased from markets in Egypt, in March 2008. All pens were allocated a reference number during this study, namely, (1) ROTO, (2) PRIMA FORMA, (3) SCHNEIDER, (4) REYNOLDS, (5) FABER‐CASTELL, (6) ZA B 1000, (7) ZEBRA, (8) STICK, (9) GHM 501/P, and (10) Bic. Experimental work was carried out on both the ink from each pen and its ink extracted from lines produced on white photocopier paper.…”

Forensic classification of ballpoint pen inks using high performance liquid chromatography and infrared spectroscopy with principal components analysis and linear discriminant analysis

“…Other analytical techniques such as thin layer chromatography, infrared spectroscopy (IR), capillary electrophoresis, microspectrophotometry and X-ray emission analysis have been applied to the analysis of inks [6,7,[9][10][11][12]. From a forensic perspective, although HPLC is a destructive method, it offers detailed information regarding the concentration of the different components of inks.…”

“…The ability to differentiate between inks can allow the forensic scientist to evaluate the authenticity of a suspicious document [6]. Inks are considered as class evidence in forensic cases, as the manufacturing involves a large-scale blend of chemicals [7]. Inks contain about 45% dyes together with solvents and additives such as resins and organic acids [8].…”

Advances of capillary electrophoresis in clinical and forensic analysis (1999-2000)

“…Vogt and co-workers [50] described the use of CE in the analysis of fountain pen and ball point pen inks. Fountain pen inks were analyzed using a 100 mM borate buffer with 20% methanol.…”