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Results were compared to thin-layer chromatography experiments to evaluate the sensitivity and performance of capillary electrophesis.A database of ballpoint pen ink analyses and common-dye reference standards has been constructed for future forensic use.Ink comparison also can determine the relationship between two samples in a forgery case that involves an original and a copy or two documents believed to have the same author.Sample authentication also can be tested based on ink analysis of raw colorant materials available during a specific historical period.To unambiguously identify specific inks, data interpretation is simplified if a chemical-separation step precedes detection of various components in ink formulations.Because of the small volume necessary for analysis, the remaining solution could be further processed using current law enforcement procedures for confirmation.Determining ink sources used on a variety of documents is a key priority for forensic document examiners.
The ability to distinguish different inks can be quite useful for several reasons.
Document alteration (e.g., at a date later than indicated) by writing with a pen of similar color but different dye composition is one specific example when ink differentiation is crucial in criminal cases.
Brewer Chemist Federal Bureau of Investigation Laboratory Chemistry Unit Quantico, Virginia Abstract | Introduction | Experimental Samples | Capillary Electrophoresis| Cationic Dye | Anionic Dye | Thin-Layer Chromatography | Laser Desorption/Ionization Time-of-Flight Mass Spectrometry | Results and Discussion | Reliability and Validation | Ballpoint Pen Inks | Other Applications | Conclusion | References Capillary electrophoresis with ultraviolet-visible photodiode array detection (190–600 nm) was studied as an alternative separation and identification tool for forensic ink examination.
Two different buffer systems were designed to analyze dye compounds in various black ballpoint pen ink formulations.
Capillary electrophoresis allows ease of sample preparation with the ability to separate and identify dye compounds based on a calculated electrophoretic mobility and a characteristic ultraviolet-visible spectrum.Protocols for capillary electrophoresis sample preparation were designed to closely mimic procedures already in place for common ink-evidence analysis.