This project, which was supported by a grant from the National Institute of Justice (NIJ), demonstrated the utility of an analytical chemistry tool that can conduct elemental analysis of ink, paper, and soil evidence quickly and with little or no sample preparation.
The researchers compared four Laser Induced Breakdown Spectroscopy (LIBS) systems to the more complex and costly Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) system used in forensic analysis. Of the LIBS systems, three are commercially available and one was built by the researchers. A major focus of this project was an analysis of the effectiveness of LIBS systems in analyzing ink and paper. The traditional nondestructive methods for ink and paper examination, such as microscopic and optical techniques, are often unable to identify the inks used to prepare a document or to determine whether questioned pages originate from the same source or have been fraudulently replaced. Also, papers and inks are constantly changing in the marketplace, so there is increased interest in finding alternative and complementary analysis methods. Overall, the study determined that the LA-ICP-MS systems have advantages in high sensitivity, minimum consumption of the sample, as well as the ability to directly characterize solids; however, they have very high costs and significant complexity. Although LIBS systems are less mature than the more complex systems, they have the advantage of improved speed, versatility, ease of operation, affordability, and portability. A total of 400 types of ink were analyzed, and about 97 percent of writing inks and up to 100 percent of printing inks were correctly identified by the LIBS system.
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