Application of capillary electrophoresis to examination of color inkjet printing inks for forensic purposes.

In the process of questioned document examination, the discrimination of inkjet printing inks is becoming more necessary due to increasingly frequent counterfeiting of documents printed by inkjet printers. Therefore, a method based on micellar electrophoretic capillary chromatography (MECC) has been developed and applied to analysis of such inks extracted from paper. With the use of an optimized and validated analytical procedure, multielectropherograms of inks taken from various models of printers made by various producers (Hewlett-Packard, Epson, Brother, Lexmark and Canon) were created. It was shown that effective differentiation of individual inks was possible in terms of migration time, order and specific shapes of characteristic peaks. By comparison of recorded UV-Vis spectra, the identification of main dyes was also achievable. The usefulness of the method was confirmed by an intralaboratory test of utility, in which several forged printouts were successfully examined. The obtained results proved that the proposed procedure is a useful tool that could be applied to ink discrimination and group identification of dyes originating from inkjet printing inks. Consequently, the developed method can be applied in the forensic field, including investigation of the authenticity of documents.