Inked up: Electrophoresis spots forged documents

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  • Published: Jul 1, 2011
  • Author: David Bradley
  • Channels: UV/Vis Spectroscopy
thumbnail image: Inked up: Electrophoresis spots forged documents

Ink-discriminate

Discriminating between original documents produced using an inkjet printer is now much easier and could be used in forensic analysis to spot forgeries and counterfeit documents. Micellar electrophoretic capillary chromatography (MECC) was developed to analyse inks extracted from paper and coupled with recorded UV-Vis spectra not only discriminates between documents from different printers but can identify the main dyes present in the inks.

Malgorzata Szafarska, Renata Wietecha-Posluszny, Michal Wozniakiewicz and Pawel Koscielniak of the Laboratory for Forensic Chemistry, at Jagiellonian University, and the Institute of Forensic Research, in Krakow, Poland, explain how inexpensive and readily available inkjet printers offer not only convenience but such clarity and resolution that they have become an important tool in document replication, either for legitimate or fraudulent purposes. As such, there is a growing need for analytical tools that can discern whether a given document is an "original" or a forgery.

The researchers explain that if a document's authenticity is dubious or its provenance unknown it is no simple matter to prove whether a questioned document is forged or genuine. After all, the team says, "The latest methods of printing used by counterfeiters produce documents of such good quality that questioned documents examinations are more and more challenging and forgeries are harder to detect." Moreover, the falsification of documents is a rapidly growing black market industry despite the advent of novel watermark technologies, special inks or paper and invisible patterns; these can all be forged with relative ease today.

Other researchers have focused on chromatographic separation methods for the analysis of inkjet printing inks, among them thin layer chromatography (TLC), high performance liquid chromatography (HPLC) and gas chromatography (GC). These all have their pros and cons. Szafarska and colleagues have turned to a novel approach essentially borrowed from molecular biology and coupled to a stalwart of the analytical laboratory UV-Vis spectroscopy to assist them in investigating questioned documents.

Ionic separation

Capillary electrophoresis, or capillary zone electrophoresis, can separate ionic compounds based on their charge and the frictional forces that are invoked when the analytes are propelled through a conductive liquid medium by an electric field. It can separate ions based on their size to charge ratio. CE has been used in myriad experiments in molecular biology laboratories since the 1960s and recently was used to analyse ink from various types of pen as well as in one limited instance inkjet printer inks. Szafarska and colleagues hoped to devise a robust and reproducible technology for such analyses based on MECC.

They have now successfully assessed their approach with a variety of inks from different types of inkjet printer from the major manufacturers. "The analysis can detect differences in the composition of inks made by different producers," the team says, "i.e. differentiation between brands." They point out that due to its high resolving power inks containing several chemically very similar substances can be discerned, which means that inks even from the same manufacturer can be identified. "This makes it suitable for evaluating the origin of documents based on the chemical composition of inks," the team adds.

In terms of obtaining strong evidence in crime or fraud investigation, the approach also allows inks used in different compatible printers to be differentiated on the basis of their MECC electrophoretic profiles. "This is a more reliable method for the determination of the ink cartridge of origin (its producer and cartridge number) rather than the printer model of origin," the team says. The team warns that off-brand ink manufacturers are a global presence in the grey markets and forensic investigators should be aware that such products might cause confusion when comparing results from documents printed with the branded ink.


The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

 Discriminating between original documents produced using an inkjet printer is now much easier and could be used in forensic analysis to spot forgeries and counterfeit documents. Micellar electrophoretic capillary chromatography (MECC) was developed to analyse inks extracted from paper and coupled with recorded UV-Vis spectra not only discriminates between documents from different printers but can identify the main dyes present in the inks.

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