Technology Trends

Imagine someone imitating your signature or changing the dollar amount on a check. How will you detect it? Things have changed since the days when Sherlock Holmes used his legendary magnifying glass. Today, crime investigators specialized in forensic science are using chromatography to identify different inks. But a new approach is described in this article by chemists and forensic scientists from the Federal Bureau of Investigation (FBI) in Quantico, Virginia. This new process, called capillary electrophoresis (CE), which permits to separate the ink into its different pigments, is automated and fast. And results can be stored in a database for future searches. Read more…

Here is the introduction of this article from the FBI.

Evidence from handwritten notes has been a hallmark of crime detection for a long time — but forensic technology has just made the process that much more sophisticated.

That’s good news for investigators of insurance fraud, currency counterfeiting, tax evasion, and insider trading violations.

Then the unknown author points at two articles published in the July 2005 issue of Forensic Science Communications. These articles are generically named “Forensic Analysis of Ballpoint Pen Inks Using Capillary Electrophoresis.”

Here are the links to these two articles, one about black inks, and another one about blue inks.

Why different articles on different colors? Black and blue inks contain dye formulations that have different properties, which requires different methods to separate the dye components.

Here is a general description of this capillary electrophoresis (CE) process.

Capillary electrophoresis (CE) has recently been used for ink analysis. A minute volume of ink (nanoliters) is injected in a narrow silica capillary filled with a buffer solution. Electrical current is then applied to the capillary to separate the ink into its components. Each component passes a photodiode array detector, which records an ultraviolet-visible spectrum. The process is automated, fast, and results can be stored electronically allowing the development of a searchable reference library. This process also detects non-dye additives in the ink that potentially can be used as identifiers.

The CE technique is largely detailed in the two articles mentioned above. But, if you’re not a chemist, I doubt you’ll understand the contents. However, the abstracts are written in plain English. Here is the one about black inks.

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. Results were compared to thin-layer chromatography experiments to evaluate the sensitivity and performance of capillary electrophesis.

Because of the small volume necessary for analysis, the remaining solution could be further processed using current law enforcement procedures for confirmation.

This technique is not limited to ballpoint pen inks and can be applied to food dyes, textile dyes, and ink-jet dyes. Here is an example taken from the article about blue inks.

Experiments have shown that food dyes, textile dyes, and ink-jet dyes can be separated and identified using the anionic and/or cationic dye capillary electrophoresis methods. Acid Yellow 23 (also known as Yellow Food Dye No. 5 or Tartrazine) was identified in a boiled-down sample of Mountain Dew soda (PepsiCo, Chicago, Illinois) using the anionic capillary electrophoresis method (Egan et al. 2005).

Finally, if you want to learn more about how the FBI is putting forensic science at work, you can read its Handbook of Forensic Services (PDF format, 181 pages, 2.70 MB).

Sources: Federal Bureau of Investigation, July 5, 2005; and various FBI web sites

Related stories can be found in the following categories.

• Chemistry
  


• Forensics
  


• Miscellaneous
  


• Police