John Chasse

The Clara Craver Award, awarded annually by the Coblentz Society, was named after Craver in recognition of her pioneering efforts in promoting the practice of infrared vibrational spectroscopy, and recognizes the efforts and contributions of young professional spectroscopists in applied analytical vibrational spectroscopy. The 2019 recipient, Xiaoyun (Shawn) Chen, a senior research scientist working in the Core R&D Analytical Sciences department of the Dow Chemical Company,has been leading Dow’s global optical spectroscopy technology network since 2013, and also the molecular structure capability since 2016, solving a broad range of problems and improving many different types of R&D and production processes, introducing many colleagues to the benefits of spectroscopy for their applications. Chen recently spoke to 

You have over a decade of experience in spectroscopic and chemometric method development for industrial research and development (R&D) and manufacturing projects, focusing on in situ reaction monitoring. What motivated you to focus on this area??

	Let me begin with how I got started. It was probably around my third year at Dow, and I was working on whatever projects that happened to come my way, when my mentor, Anne Leugers, handed me two attenuated total reflectance (ATR) dipper probes, which were no longer needed by another group, and told me to explore whether I could make use of them. By chance, several colleagues in our engineering and process science group reached out to us to monitor a low-temperature reaction that they could not seem to grasp with conventional off-line methods such as gas chromatography (GC), liquid chromatography (LC), or nuclear magnetic resonance (NMR) spectroscopy. We borrowed another Fourier-transform infrared (FT-IR) instrument from our process analytical group, so that we could use the ATR dipper probe to monitor that reaction. In situ monitoring immediately helped us to detect and prove the existence of a highly labile intermediate, which explained why earlier off-line analysis failed. The focus of the project then shifted to characterizing the reaction kinetics for process optimization, and, as a result, we needed to find a way to quantify the concentration of all reaction species. I was very fortunate that Randy Pell, a world-renowned chemometrician, became my mentor in chemometrics, and together we were able to apply several chemometric tools such as classical least squares (CLS) and partial least squares (PLS) to quantify all the reaction species within the complex mixture. This work was later published externally (1)

	So, that was how I got started-as a confluence of instrument and probe availability and project need. I was truly amazed by how useful and enabling in situ spectroscopy turned out to be. The results from in situ infrared (IR) substantially impacted the direction of that particular project and the work of multiple PhD-level process chemists and engineers. As encouraged by my mentors and my leaders, I started to make an intentional effort to further explore and identify similar opportunities. Very quickly, it became apparent to me that the in situ spectroscopy project was not a lucky one-off, but that there were actually many projects that would benefit. Even though people might not know how they could benefit from in situ spectroscopy, I took it upon myself to champion the application of in situ spectroscopy throughout Dow, and even outside. Since then, I just became naturally drawn to that method, and often had to force myself not to be solely focused on in situ spectroscopy. I truly believe that in situ spectroscopy can be a revolutionary tool for process monitoring.

How broad is the range of projects that you work on? Are the projects very similar to each other, or diverse?

	Extremely broad. Let me start with types of projects. Currently, I have several projects dealing with silicone, a few dealing with catalysts ranging from zeolites to MOF, one related to radical polymerization, one related to polyurethane foaming, several related to ethylene polymerization, and several related to customer applications, such as paper coating and airbag coating, among others. In terms of commercialization stages of these projects, they may range from early stage concept-shaping, to process development, to customer applications. There is never a dull moment as far as projects are concerned. The only common theme among them all is that they all can benefit from the use of optical spectroscopy.

What are the biggest challenges you tend to encounter in your work?

	Time management, motivating others, and delegation. There are many things you need to do well as an industrial analytical scientist. First, you need to make sure that you are working on important and relevant research topics. In my current role, I also need to make sure that we keep abreast of the latest analytical instrument development, so that we can solve the toughest analytical problems with the newest tools. We also need to deliver on existing projects, look out for new projects, document past projects, and mentor new people. Whether you can manage your time well among all the above-mentioned tasks is critical in determining how fulfilled, productive, and successful you can be. I forgot to mention that additionally you may also need to maintain an external presence, and I do that by serving as the newsletter editor for the Society for Applied Spectroscopy (SAS), and on the board of the Coblentz Society, and by continuing to publish in peer-reviewed journals. Motivating others and delegation are things that aren’t necessarily taught at graduate school, but become increasingly important as you progress through your career. They are often easier said than done, and I am fortunate to have several great leaders and mentors who have been coaching me throughout this process. I don’t feel I am an expert in them yet, but am trying very hard to be better at them.

You recently published a study about monitoring polyimide production using a combination of in situ infrared and Raman spectroscopy (2). Why did you use both techniques in the study? What was different about what the two techniques enabled you to see? Can the results of that study guide your choice for IR or Raman spectroscopy for future studies?

	The short answer to your first question is “because we can.” I routinely take an IR, Raman, and near-infrared (NIR) spectrometer with me when I visit my colleagues at their labs. Sometimes there’s a clear winner regarding which type of spectroscopy will be the best fit, and we’ll just use that. Just as often, we cannot really predict which technique will work best, and then we try all of them. Which technique is the most appropriate also depends on the focus of the project, which may continue to shift as we make progress.  Often optical spectroscopy may not be the right tool, and then we’ll bring in other analytical tools as well, though that’s probably outside the scope for this interview. You’ll have to read that paper to see our exact findings. For this particular study, I would say both techniques would eventually lead to similar findings, though your perspective into the reaction progress would be very different, due to the different selection rules. Another advantage of using such a broad range of techniques lies in the insights potentially offered by them. There have also been numerous times when we originally set out to solve one problem, but discovered something totally unexpected, which led the whole project to take on a new direction.
	
	

What do you consider to be the most satisfying aspects of mentoring junior spectroscopists, as well as introducing those unfamiliar with spectroscopy to the techniques?
	

As I am starting my 12th year with Dow, I am also starting to take on new roles, and one of the most important ones is to mentor young people coming to our group. I feel very lucky that I have the chance to interact with the brightest minds coming out of graduate school, and I feel especially privileged to see that such bright young people actually take on my advice as they start to navigate their first “real world” job. Seeing their maturing into driven and motivated researcher is the most satisfying part. As for introducing spectroscopy to those outside the field of spectroscopy (which is the case for ~98% of the colleagues I interact with), that’s almost an infinite source of joy for me. I can still vividly remember the first time when my friend Doug Bland told me that he didn’t believe my in situ IR results, because they didn’t line up with the earlier GC results he had been getting for two years, and his subsequent “conversion” and full embracement of in situ spectroscopy. Changing people’s minds and attitudes is often the most challenging part, but definitely the most rewarding part when you manage to do so. I now have many colleagues who no longer treat in situ spectroscopy as the last resort after they cannot use GC or LC, but rather first try to monitor their reactions with IR or  |||||||||||Raman, and only move on to GC or LC |when IR and Raman don’t work sufficiently well (which does happen from time to time). I’m very proud of this.

What do you think are the aspect of working in industry that scientists in academia don’t understand or appreciate?

	I am not sure whether it is true that academic scientists don’t understand or appreciate industrial scientists. Everyone has his or her own focus and perspective. Even within my own group, I don’t think I always understand or appreciate the importance of another fellow spectroscopist’s work. For example, I have fellow spectroscopists who spend all their time in QC labs or QC method development, and colleagues who devote themselves to process analytical, and still others whose focus was on the data management side, such as library, data communication, and chemometrics. I think we all need to put ourselves into others’ shoes to really appreciate each other more. Along the same lines, maybe it’s really the diverse type of work we do in industry that may be something not fully understood or appreciated by outsiders. We also face very different types of pressure in industry. While we usually do not get stressed out by funding or teaching, there are many other things that you have to keep abreast of to do your job well, such as keeping up with the latest technology development, ensuring a robust project pipeline, creating a roadmap to ensure that we have the most relevant capabilities matching the company’s direction, and last, but not the least, meeting the ever-changing customer and market needs.

 28(5), 319-489 (2014). DOI: 10.1002/cem.2507

 71(9), 1-8, (2017). DOI: 10.1177/0003702817700427

Articles

Xiaoyun (Shawn) Chen of Dow Chemical solves a range of analytical problems in R&D and production processes using in situ spectroscopy and chemometrics.

Advancing In Situ Applications of Spectroscopy in an Industrial Setting

In recent years, consumers are increasingly opting for natural and organic food. This has led many food producers to switch from using artificial ingredients to using natural ones. In some cases, however, questions arise about the authenticity of those ingredients. Lili He, an associate professor in the Department of Food Science at the University of Massachusetts, Amherst, focuses on developing and applying advanced analytical techniques to solve critical and emerging issues in food science. Recently, that focus has turned to using surface enhanced Raman spectroscopy (SERS) in the detection, analysis, and identification of both natural and artificial food colorants. Dr. He recently spoke to 

You have developed a SERS-based method that is capable of detecting and identifying common food colorants (1). What motivated you to undertake this work?

	Currently in the United States, there are seven main artificial colorants, and about 25 natural colorants, that are approved for use in food. There has been growing interest in the food industry in replacing artificial colorants with natural alternatives, mainly because consumers are increasingly demanding products with natural ingredients. However, the authenticity of colorants used in food products has raised increasing concerns. Natural and artificial coloring agents can be visually identical, so any detection method would need to be able to provide information about the chemical composition of the colorants that are present. We believed that SERS could be an effective method for colorant detection and identification.

Why is SERS a good technique for analyzing food colorants?

	Colorants with conjugated bond systems are inherently Raman active, and given that Raman spectroscopy measures molecular signatures as a basis to identify the components of a mixture, it can be used to differentiate between visually similar colorants with different molecular structures. In SERS, the detection sensitivity of Raman spectroscopy is enhanced by a nanoparticle substrate. In addition, since each colorant produces a unique spectrum, it is feasible to detect multiple colorants in food. Detecting compounds in food matrices with SERS also has the advantage of being simple and rapid, with minimum sample preparation.

What factors did you consider in your choice of SERS substrate?

	In developing the method, we considering the perspective of potential end-users of the method-people who work in the food industry or in food regulation. Therefore, we chose a simple silver nanoparticle substrate that is commercially available, so that the method and database can be easily transferred to the end users, who should not have any difficulty obtaining the substrate.

	We successfully demonstrated the feasibility of SERS to rapidly detect colorant adulteration, as well as to identify colorants in real commercial food products. Also, we have established a database of all the artificial colorants, and most of the natural colorants, and even some banned colorants. We believe that it is important to include banned colorants in the database, because banned colorants pose great safety concerns to public health. Each colorant has a unique SERS pattern based on its molecular vibrations.

How well did the technique perform on actual food products, compared with its use on aqueous solutions of colorants?

	We successfully detected and identified colorants in several real food matrices, including breakfast cereals, candies, crackers, and juices which used artificial or natural colorants. This technique works very well on actual food products, due to its high sensitivity to colorants; there is no significant interference from the background matrices.

	We will further expand and validate the database to cover all FDA-approved food colorants and banned colorants of concern. We will also explore the use of SERS to study interactions between natural colorants and food ingredients that can affect the stability of colorants. In addition, we will carry out a market survey of a variety of commercial food products claiming to contain natural colorants to identify possible cases of adulteration and mislabeling of colorants and to assess the prevalence of such cases.

	We hope that, after successful completion of that study, we will be able to establish a complete SERS spectral database for certified and exempt colorants regulated by the FDA, as well as for selected banned or unapproved colorants. We also hope that we will gain knowledge about the stability of natural colorants in different food matrices by studying interactions between colorants and food ingredients. In addition, we hope to generate information about the current levels and nature of colorant adulteration and misleading labeling in the food market. The developed method and database could be used by industry to assess the quality and authenticity of purchased colorants, as well as to study their degradation kinetics in food and beverage products. Government agencies could also use the methods for rapid screening of any illegal use of food colorants in food products, whether that screening occurs on site or in a laboratory. Information obtained from this project would help industry improve food quality and safety, as well as assist government agencies in making decisions about regulatory considerations and actions regarding food colorants. These actions would lead to a sustainable food colorant market of high quality, reliability, and safety. Therefore, the outcome of this project will benefit the long-term stability of the U.S. food system.

	(1) J.C. Gukowsky, T. Xie, S. Gao, Y. Qu, and L. He, 

 is Associate Professor of Food Science at University of Massachusetts, Amherst. She received her PhD degree from University of Missouri-Columbia in 2009 and did her postdoctorate training in University of Minnesota between 2009 and 2012. Then she joined the faculty in the Food Science Department at the University of Massachusetts, Amherst as an Assistant Professor in 2012. Dr. He's major research focus is to develop and apply the most advanced and innovative analytical techniques to help solve critical and emerging issues in food science. Her group has developed various surface enhanced Raman scattering based techniques for food safety and food chemistry applications. Dr. He has successfully obtained external funding (over $1.8 M as PI) from federal and industry sources, and published 82 papers. Her excellence has been recognized by receipt of the 2012 Young Scientist Award from the International Union of Food Science and Technology, 2015 ACS-AGFD Young Scientist Award, 2016 Young Investigator Award from Eastern Analytical Symposium, 2016 IFT Samuel Cate Prescott Award for Research, and was selected as one of the Talented 12 by 

SERS is a method that is receiving new attention in the detection, analysis, and identification of both natural and artificial food colorants. Lili He, at the University of Massachusetts, Amherst, recently spoke to Spectroscopy about this important analytical work.

Detecting and Identifying Food Colorants with SERS

Spectroscopy can be difficult to carry out outside a controlled laboratory environment. Imagine, then, the hurdles that would accompany performing spectroscopy in the extreme conditions of deep space or the ocean floor. Mike Angel, a professor of chemistry at the University of South Carolina, has taken on those challenges, working on new types of instruments for remote and in- situ laser spectroscopy, with a focus on deep-ocean, planetary, and homeland security applications of deep ultraviolet (UV), Raman and laser-induced breakdown spectroscopy (LIBS), to develop the tools necessary to work within these extreme environments. A key development is the spatial heterodyne Raman spectrometer, a fixed grating Fourier transform Raman spectrometer. For this development and other work, Angel has been awarded the Lester W. Strock Award from The New England section of the Society of Applied Spectroscopy, in recognition of a selected publication of substantive research in, or application of, analytical atomic spectrochemistry in the fields of earth science, life sciences, or stellar and cosmic sciences.

A past awardee of the 2012 and 2018 Society of Applied Spectroscopy William F. Meggers Award (for published work on spatial heterodyne Raman spectroscopy) as well as their 2018 NASLIBS Award (for remote LIBS using spatial heterodyne spectrometer), Angel, who will receive the Strock award this fall at SciX 2019 in Palm Springs, California, took the time to speak to us about his recent work. This interview is part of a series of interviews with the winners of awards that are presented at the SciX conference.

A recent paper you co-authored (1) discusses the initial demonstration of a deep-ultraviolet (UV) 244 nm excitation spatial heterodyne Raman spectrometer (SHRS), and you mentioned that one of the motivations for developing such a device is planetary exploration using a lander or rover. Later in the paper, you discuss the limitations of Raman spectroscopy in such an environment. Would you briefly summarize these limitations, and how this device will overcome them?  

	Raman issues include poor sensitivity, 0.1% in many cases, and luminescence interference. Deep UV excitation (<~250 nm) gets around the fluorescence issue by shifting the Raman spectrum to a wavelength range where most things don’t fluoresce. Using 244 nm excitation, for example; even CH stretch bands are below 265 nm, and most things don’t fluoresce at such short wavelengths. You can also avoid a lot of fluorescence using near-infrared excitation, at say 785 nm, but in this case, the Raman signal can be much lower, because of the smaller Raman cross section at red wavelengths. The Raman scattering efficiency goes as the inverse 4

 Raman band, using 244 nm excitation, has more than two orders of magnitude larger cross section than the same band using 244 nm excitation. This doesn’t mean you will necessarily get 100 times more signal using 244 nm excitation, because there are other considerations, such as sample penetration depth. Deep-UV also offers another signal advantage, resonance enhancement. In this case, resonance can provide another several orders of magnitude larger Raman cross section. So, the potential is there to get much higher sensitivity using deep-UV excitation. Traditionally, UV spectrometers are large, because of the need for very high spectral resolution, which typically requires a high dispersion path. The SHRS technique allows high spectral resolution in the deep-UV, in a relatively small footprint. 

Another paper you co-authored (2) focuses on combining remote LIBS and Raman spatial heterodyne spectrometers to measure a variety of organic and mineral samples, including materials from deep ocean hydrothermal vents, at a distance of 10 m, using a ~100 mm diameter Fresnel lens as the collection optic. What would be the expected discoveries? Who do you feel would be the beneficiaries of this work? 

	The discovery of organisms that can survive in environments like deep-ocean hydrothermal vents has changed our way of thinking about where life can evolve. These kinds of places might be similar to where life got started on Earth, or might have started on other planets. Studying these places is important to understanding ocean chemistry, but also to understanding the extremes in which life can thrive. Hydrothermal vents are believed to have existed once on Mars, and such locations would be good candidates to explore in the search for signs of past life there. Making chemical measurements at deep-ocean vents is hard, because of the depth, and extreme temperature and pressure, and because chemical sensors that can be used under these extreme conditions are rare. The ability to use remote LIBS and Raman to analyze the elemental composition of hydrothermal vent fluids would greatly expand the amount of chemical information that could be obtained in a limited time. 

You recently co-authored a paper on coupling a spatial heterodyne Raman spectrometer (SHRS) with millimeter-sized optics with a standard cell phone camera as a detector for Raman measurements (3). What prompted you to address this development? Would you explain what is unique about this development and its purpose?

	The driver for this study was planetary exploration, to places like the outer Jovian moons, where spacecraft instruments size and weight are at a premium. I wanted to demonstrate that a truly miniature Raman SHRS spectrometer was feasible. It occurred to me that a cell phone already has a high resolution CMOS CCD detector, though uncooled, and a miniature collection lens of very high quality, built in. So, all we had to do to make a miniature Raman spectrometer was mask down the gratings on our existing SHRS, to a couple mm in this case, and add a relatively low power laser. It worked so well in large part because the throughput of the SHRS was very high, and CMOS detector technology is really good and relatively low noise, even uncooled. I found out when doing background research for the paper that a cell-phone Raman spectrometer had not yet been published, so that was fortunate for us.

I’m struck by the range of research work your group is involved with. Are the projects you are working on very similar to each other, or diverse? How do you choose the projects? What are the biggest challenges you tend to encounter when working within these topics?

	To me, all of our work is very closely related. I’ve been working for years to make spectrometers and chemical sensors that can be used to make measurements in hostile environments. Whether it's the deep ocean, the surface of Mars, or a battlefield, the challenges are similar. Most projects come about by talking to people about their measurement needs and problems. It almost always starts with the need. The biggest challenge is long term funding. I have been very lucky to have had long term support from NSF and NASA. 

What does being awarded the Lester W. Strock Award mean to you?

	I feel incredibly honored, especially looking at the list of previous award winners. This award is traditionally for work in atomic spectroscopy, and even though I do a lot of work using LIBS, an atomic spectroscopy technique, I think of myself mostly a molecular spectroscopist. So, I was very surprised by the award, and I am very thankful.

Mike Angel is a Professor of Chemistry at the University of South Carolina where he has held the Fred M. Weissman Palmetto Chair in Chemical Ecology since 2005 and was named a Carolina Trustee Professor in 2013. He received his PhD from North Carolina State University in 1985 and carried out postdoctoral work with Tomas Hirschfeld at Lawrence Livermore National Laboratory. Angel’s research group’s recent work includes developing the spatial heterodyne Raman spectrometer (SHRS), and exploring the SHRS for deep UV Raman, remote Raman, and for use on future planetary landers and SmallSats. Angel is a member of the Mars 2020 SuperCam science team (2014) and is an elected Fellow of AAAS and an SAS Fellow.  He has been a SAS Tour speaker, an A-Page Advisory Panel member for 

 and an editorial advisory board member of 

, and a member of the scientific committee of NASLIBS and the International LIBS conference.  Other honors include the 2018 and 2012 SAS William F. Meggers Award, 2018 NASLIBS/SAS Award, 2016 Elected Fellow of the Society of Applied Spectroscopy (SAS), 2015 Southern Chemist Award, 2014 Science Team member for Mars 2020 SuperCam instrument, 2013 Carolina Trustee Professor, 2012 ACS South Carolina Chemist of the Year Award, 2011 Federation of Analytical Chemistry & Spectroscopy Societies (FACSS) Innovation Technology Award, 2011 

and 2006 Lawrence Livermore National Laboratory Physics and Advanced Technologies Directorate Award.

Spectroscopy can be difficult to carry out outside a controlled laboratory environment. Imagine, then, the hurdles that would accompany performing spectroscopy in the extreme conditions of deep space or the ocean floor. Mike Angel, a professor of chemistry at the University of South Carolina, has taken on those challenges, working on new types of instruments for remote and in- situ laser spectroscopy, with a focus on deep-ocean, planetary, and homeland security applications of deep ultraviolet Raman, and laser-induced breakdown spectroscopy to develop the tools necessary to work within these extreme environments. 

Developing Spectroscopy Instruments for Use in Extreme Environments

Laser induced breakdown spectroscopy (LIBS) has been applied as quantitative and qualitative analytical method for a variety of matrices. A paper published in the journal 

 in 2018 (1) was chosen by from the North American Society for LIBS (NASLIBS) and the Society for Applied Spectroscopy (SAS) as the best paper on the topic of LIBS. In this paper, a molten salt aerosol–laser-induced breakdown spectroscopy (LIBS) instrument was used to measure the uranium (U) content in a ternary UCl

–LiCl–KCl salt matrix to investigate the development of a near real-time analytical method. This method development was intended to be applied for uranium material safeguards and accountability. Five different uranium concentrations were used to determine the analytical figures of merit. In the analytical development work, three uranium emission lines were used to develop univariate calibration curves; these included 367.01 nm, 385.96 nm, and 387.10 nm lines. Both univariate and multivariate calibration approaches were tested for uranium content, with a multivariate partial least squares (PLS) model achieving the optimum analytical results, with a root mean squared standard error of cross validation (RMSECV) of 0.085 weight percent. The award-winning paper concluded that the aerosol-LIBS system was capable of monitoring the uranium concentration for the normal operational uranium levels of pyroprocessing molten salts. We spoke with Ammon Williams, the primary author of this paper, who is currently with the Idaho National Laboratory (INL), about this work.

Your paper examines measuring the accumulation of special nuclear materials in molten salt during the processing of spent nuclear fuel. Why is this a concern? Why is LIBS a useful technique for this purpose?

	The main concern is material accountancy of the actinides, specifically uranium and plutonium in the molten salt throughout the different processes. This, of course, is a legal requirement from the International Atomic Energy Agency (IAEA), and is good practice to ensure nuclear materials are used for peaceful purposes. The reason that this research is so important is that there are limited near-real time and in situ analytical approaches to measure actinide concentrations in the difficult hot cell environment required for electrochemical processing of spent nuclear fuel. LIBS is an attractive analytical approach for material tracking, as it can be performed remotely, quickly, and under harsh conditions. In addition, it is essentially a non-destructive technique, and, more importantly, it does not require that a physical sample be removed from the processing environment or mass balance area.   

Would you explain the differences between standard LIBS sampling techniques and the molten salt aerosol–LIBS instrument that you have developed?

	The LIBS aspects of both techniques are the same in that a laser pulse generates a plasma in which characteristic light is collected to generate a spectrum. The distinguishing feature is the novel approach utilized to prepare the liquid sample for LIBS analysis. In the electrorefining process being monitored, the molten salt is in a liquid form, which is difficult to sample via LIBS, due to splashing, surface perturbations, and surface layers. In the aerosol approach, the liquid salt is drawn and aerosolized prior to LIBS sampling, which reduces many of these challenges.  

What are the main advantages you discovered by using a multivariate approach, rather than a univariate one? What led you to select partial least squares (PLS) over other multivariate calibration approaches?

	The key advantage I found with using a multivariate approach is that it allows for more complex sample matrices. In most of the laboratory work I have done, I know what is in the sample, and can identify spectral lines that have low interferences. However, in the actual electrochemical process, the salt will contain large amounts of actinides, rare earth chlorides, and other elements that are notorious for having complex and busy spectra. In that sample matrix, it would be significantly more difficult to perform a univariate calibration than it would be to perform a multivariate calibration approach. We selected the PLS multivariate method, as it is a standard approach, and one in which we felt was suitable for our application.

Tell us a little bit about the LIBS technique you utilized to perform this task, and why you believe that was a good analytical method choice for this analysis. What particular factors did you consider in your selection of this analytical technique?

	In this research, we used optical windows and mirrors to deliver the laser pulse into our glovebox (argon gas environment), and then used fiber optic feed throughs to transport the LIBS signal to an echelle spectrometer outside the glovebox. With this approach, only light was passing through the containment system. In my application, a suitable analytical technique needed to be adaptable to in situ implementation, provide timely elemental information, and require minimal sample preparation and handling. The LIBS analytical technique was highly suited for these constraints, as it can provide in situ and timely analytical information about the sample with minimal sample preparation in harsh nuclear applications (for example, high temperature, radiation, corrosive).

Is there anything that you’ve done in your study that is different from what other researchers have done as they examined the same problem?

	Other research in this area focused on applying LIBS to either solid salt or the liquid surface of the salt. Both approaches have strengths and weaknesses. In this research, we approached the problem differently by applying the LIBS analysis to a molten salt aerosol.

What were the most serious challenges that you encountered while developing this approach? How did you overcome them?

	The first challenging aspect was developing a method to generate molten salt aerosol droplets at extremely high temperatures and in a highly corrosive environment. This was overcome by modifying a collison-type nebulizer with appropriate materials, seals, and heating. Another serious challenge encountered was developing a sampling chamber that allowed for light into and out of the sampling stream, while preventing particle buildup on the optics. Both of those challenges, and many others, were overcome with persistence, brainstorming, and many design iterations.

Are you pleased with the results you have you achieved so far? What are your next steps in this work?

	I am pleased; it was extremely challenging to develop this system, and achieving a successful result was very satisfying. Going forward, we would like to optimize the aerosol system configuration to reduce optical degradation and increase stability. In addition, we want to test the system in more complex salt matrices, including additional uranium samples with multiple rare earth elements.

What are some major gaps in knowledge in the use of LIBS that you would like to see more research and development time devoted to?

	With the traditional LIBS approach, it is difficult to determine isotopic information of materials without expensive high resolution spectrometers. For nuclear material accountancy purposes, having the ability to determine the actinide isotopic information in our samples is an important goal. An emerging technique called laser ablation molecular isotope spectroscopy (LAMIS) is similar to LIBS, but gates the detector significantly later to allow for molecular recombination. In this process, isotopic shifts become greater, and the spectrometer resolution requirements can be more relaxed. I am interested in seeing more research in this area, specifically with regards to complex, mixed actinide samples, like we expect to see in nuclear safeguards applications.

What is your general approach to problem solving in your scientific work?

	My research motto is: think, apply, learn, and refine.

What does receiving the NASLIBS/SAS Best Paper Award personally mean to you?

	I am deeply honored to receive this award, and I appreciate the recognition for my work.

		A Williams and S. Phongikaroon, Laser-Induced Breakdown Spectroscopy (LIBS) Measurement of Uranium in Molten Salt. 

Ammon Williams received a BS degree in Mechanical Engineering in 2009 from Brigham Young University–Idaho. He then studied Chemical Engineering, and earned a MS degree in 2012 from the University of Idaho. Finally, Williams received his PhD in Mechanical and Nuclear Engineering from the Virginia Commonwealth University in 2016 for his dissertation titled, “Measurement of Rare Earth and Uranium Elements using Laser-Induced Breakdown Spectroscopy (LIBS) in an Aerosol System for Nuclear Safeguards Applications.” Since graduation, he has worked as a research scientist at the Idaho National Laboratory. Dr. Williams’s current research interest are nuclear safeguards and nonproliferation, and, more specifically, analytical techniques and approaches to monitor special nuclear materials (uranium and plutonium) in harsh and remote environments. Williams has made significant contributions in the area of molten salt LIBS, as well as other measurement approaches, such as electroanalytical and bubble level measurement techniques.    

Laser induced breakdown spectroscopy (LIBS) has been applied as quantitative and qualitative analytical method for a variety of matrices. A paper published in the journal Applied Spectroscopy in 2018 (1) was chosen by from the North American Society for LIBS (NASLIBS) and the Society for Applied Spectroscopy (SAS) as the best paper on the topic of LIBS. In this paper, a molten salt aerosol–laser-induced breakdown spectroscopy (LIBS) instrument was used to measure the uranium (U) content in a ternary UCl3–LiCl–KCl salt matrix to investigate the development of a near real-time analytical method. We spoke with Ammon Williams, the primary author of this paper, who is currently with the Idaho National Laboratory (INL), about this work.

Author | John Chasse

Articles

Advancing In Situ Applications of Spectroscopy in an Industrial Setting

Detecting and Identifying Food Colorants with SERS

Developing Spectroscopy Instruments for Use in Extreme Environments

Using LIBS to Track Uranium Materials