New tool, new opportunities
SciAps created the world’s first handheld LIBS primarily to help the metals analysis industries more profitably verify carbon and carbon equivalents at rugged or remote job sites. But it didn’t take long for researchers around the world to begin exploring an array of diverse applications—many of which are mentioned on the SciAps website—opening the door to a universe of new business opportunities rooted in elemental analysis.
As a partner in SciAps Academic Loaner program, Dr. Richard Hark, a synthetic organic chemist by training who now works as a conservation scientist, enthusiastically added the instrument to his research tools. Here are some of the novel ways Dr. Hark has applied the handheld LIBS over the past several years.
Creating a library of samples from mines in conflict regions
In order to build on the initial success that Dr. Hark and his collaborators had with sourcing geographically diverse samples of columbite-tantalite using LIBS, he recognized that it would be necessary to create a fairly comprehensive library of minerals from verified locations. In order to acquire the necessary samples, he partnered with a major consumer electronics company as well as collaborators with experience working in conflict regions. “What you really need to obtain a more definitive answer, people could make a case that the minerals came from a different mine. Plus, it’s a shifting landscape. The militia might control these ten mines one month, and then they might control more mines six months later,” says Hark.
Hark’s involvement in this U.S. project ended when the Washington, D.C., Circuit Court ruled that the Dodd-Frank Act supply chain requirement violated the prohibition against compelled speech. However, he still believes that using handheld LIBS to identify samples unique to individual mines is a promising way to contribute to solving this complex geopolitical-economic problem.
Attributing spent ammunition cases in combat areas
Even though there are a number of companies who manufacture unmarked ammunition, Hark worked with a group on identifying the manufacturer of cartridge casings collected in a conflict area. These were boots-on-the-ground people who would scoop up spent cartridge casings after a firefight to have evidence of not only who the combatants were, but also where they were getting the kit required to prosecute their conflict. “So, we looked at the brass to give them answers,” says Hark.
This was a small, pilot project with the LIBS, but this unique application has the potential to provide useful answers about conflicted areas.
Firewood analysis helps close a murder case
The analysis of wood using LIBS is a new and relatively unexplored area. One report Dr. Hark was familiar with involved forensic analysis of wood obtained at a crime scene where a body was burned. Dr. Hark summarized the analysis in a book chapter on forensic applications:
“LIBS analysis of wood figured prominently in a murder investigation in Collin County, Texas, in 2004 in which a suspect tried to dispose of a body by burning it on a pyre made from firewood. Ten logs were recovered from the crime scene along with four logs the suspect brought to a party near the time of the murder; all 14 logs were partially burnt. … a researcher at Oak Ridge National Laboratory who was using LIBS to study wood, was asked to analyze 11 of the samples. Emission spectra were obtained for burnt and unburnt areas of all 14 logs …. The LIBS spectra for all samples showed lines corresponding to C, N, Ca, Al, Fe, Ti, Si, Mg, Mn, and Na and were identical by visual inspection. Significantly, there was no apparent difference between the unburned wood and the charred logs. Full spectra were used to perform correlation analysis and the researchers reported they were 99.999% confident that the spectra of the logs were identical. They concluded that ‘‘for such a level of statistical significance to be achieved, it is highly likely that the logs came from the same tree, or at least from the same stand of trees growing in a very restricted locality.’”
The evidence never made it to the trial. “It probably would not have held up in court, but it apparently contributed to the evidence that caused the person to confess,” says Hark.
Virtually unlimited applications for forensic science
With SciAps instruments designed to analyze very small parts, LIBS can analyze many materials in forensic cases, such as glass (fragments from building windows, beverage containers, automobile windows, headlights or mirrors), paint (chips or smudges), ink and paper (falsified business transactions, counterfeit currency, or art forgeries), textile fibers (type, color and kind of dye used), biological materials (plant, animal, bone, teeth, hair, nails), and nuclear and radiological materials (pre-detonation and post-detonation forms). The use of handheld LIBS for forensic purposes has significant potential to provide fast material identification and classification of evidence, with the added benefit of being able to be carried out in the field. All of these applications are discussed in Dr. Hark’s chapter on Forensic applications of LIBS.
Expanding conservation in public and private collections
A current decorative arts project Dr. Hark is working on at Yale is trying to identify mahogany and mahogany look-a-likes. “This is wood that is not true mahogany in a botanical sense, but rather can look like mahogany if it’s in a piece of furniture, for instance,” says Hark. This LIBS application is important for conservators and curators. Through the analysis, they hope to better understand their collection and the raw materials used to produce furniture. The ability to distinguish mahogany from other woods that look similar to it, without damaging highly valuable 18th century pieces is of great use to the Yale University Art Gallery. LIBS offers a minimally invasive analysis technique. “It could be applied as a screening tool or presumptive method—not necessarily totally confirmatory, but frequently good enough. We hope to answer questions that are of interest in the decorative arts field,” says Hark.
Another decorative arts application for the LIBS was identifying if a piece of Chinese jewelry was gilded or electroplated or a solid silver alloy. Most precious metals analysis is performed with XRF, but Dr. Hark could not use XRF because it is a bulk analysis tool that would not give the needed information about the surface of the object. “The stratigraphic ability of LIBS is something we can’t get with the XRF,” says Hark, so he used the LIBS instead. He chose an innocuous area and used several pulses to determine that the jewelry had a coating of silver.
Defining the historical record
Dr. Hark has also collected seashells from various beaches around the world to analyze their chemical signature.
“The LIBS plasma formation and light emission process is more than just chemistry. It also relates to physical properties, like the hardness of the material. All that gets folded into the full spectrum,” says Hark. This information could be used to draw interesting conclusions about shells found in archaeological digs.
But as with most projects like this one, it’s a matter of having enough samples to have a robust library to adequately represent the variation that exists among the geographic locations. To this end, Dr. Hark has worked with Dr. Russell Harmon, a geologist and longtime LIBS collaborator, to develop extensive collections of samples, including obsidian from the America West, volcanic rocks from all the continents, and garnets from all over the world. “As a chemist who usually works in a laboratory, I have enjoyed the opportunity to get out and do some field work occasionally,” Hark said.
Dr. Hark has also analyzed sherds of pottery from the 1619 church in Jamestown to identify possible connections between pottery and the settlers. “The archaeologist at Jamestown now has a LIBS unit. The plan is for me to work with them to design some research projects,” says Hark. It’s possible to identify what people tossed into wells and compare it to the well-kept records during specific timelines at Jamestown. “It’s really fascinating to dial back the clock, in a sense, and look at a sherd and consider who could have made the pottery or who ate from the plates and drank from the cups.”
Time will tell if archaeologists find a connection between the pottery and Pocahontas, John Rolfe, or Captain John Smith.
Any industry you can think of, there’s an application for handheld LIBS waiting to be discovered by a business looking to expand. “When I first got involved with LIBS back in 2003, I never expected that it would take me in so many directions and lead to multiple fascinating projects with outstanding collaborators,” Dr. Hark reflected.
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