Evolution of the ICP-MS Application Landscape 

40 Years Old and Still Solving Problems

Introduction to Organic Nitrogen Polymers

Infrared Spectroscopy of Polymers, XI

Is a Recession Looming— or Even Already Here?

The 2023 Spectroscopy Employment and Salary Survey

Determining the strength of a piece of steel, especially the stainless steel used in everything from car manufacturing to construction, is vitally important in keeping drivers and passengers safe during crashes and preventing the collapse of buildings. Predicting the strength of a steel prototype accurately, based on its microstructure and composition, would be extremely helpful in the design and manufacturing of new and improved types of that alloy. However, that ability has been impossible to achieve—until now. Harishchandra Singh, Graham King and associates have employed high energy synchrotron X-ray diffraction (HE-SXRD) experiments and an analytical model in order to predict the yield strength of cerium-modified super duplex stainless steel 

SDSS) subjected to various cold- and cryo-deformation. 

 recently had the opportunity to discuss the experiments and the findings with Singh and King.

Your paper (1) offers a new high energy synchrotron X-ray diffraction (HE-SXRD) method to predict the yield strength for highly alloyed complex steel. Why do you feel a “new way” was needed?


An ultra-fast methodology with accuracy is always beneficial. The yield strength of a steel is a result of many microstructural factors inside. The more complex the microstructure the more complicated is to know their individual contribution to yield strength. Conventional approaches measure yield strength easily but not the mechanism of strengthening. HE-SXRD in combination with analytical models do the same job in an hour precisely. This ultra-fast precise approach can help to optimize the high strength steel in a faster way.

Were you surprised that you could apply HE-SXRD to accurately predict the yield strength of deformed variants of Ce-modified stainless steel? Were your results as expected?


Indeed, we expected it would work but not that precisely! Yes, since HE-SXRD provided all existing microstructural factors affecting yield strength, this helped the prediction accurately.

Briefly describe the HE-SXRD method, and how this method differs from what was previously done by yourself or others.

Briefly, HE-SXRD (high energy synchrotron X-ray diffraction) probes the crystalline structure of bulk materials even with a few mm thickness because of its high penetration power. Lab based XRD mostly allows information from a few hundred of micrometers. To the best of our knowledge, this methodology has not been realized before to this accurate extent.

It was noted that the process described could also help to engineer novel steels through a better understanding of the relationship between a steel’s microstructure and its mechanical properties. How could this be accomplished and why is this important?


Steel consists of complex microstructures which need to be investigated to realize its strength. If you know the microstructure details, you can design high strength steel in a better way. As pointed out, a steel’s microstructure highly affects its mechanical properties, and therefore one needs to know the full information about existing microstructures within a bulk steel. Due to many limitations, conventional methods may be unable to provide the full details in a time effective manner. The same can be easily probed using advanced methods such as HE-SXRD due to high photon flux and penetration power. Full knowledge is important because the type of microstructures decides the strength of steel.

What is the main benefit in using HE-SXRD to predict the yield strength of steels as opposed to other spectroscopic methods?

HE-SXRD can be applied to bulk whereas most of the spectroscopic methods deal with surface and require dedicated sample preparation. Scaling the obtained information from spectroscopic methods is another concern.

Did you encounter any challenges or obstacles in developing this method? How did you overcome them?

Yes, a lot actually, because of rare literature on such methods. Already collected experimental yield strength data helped as the reference point for this method. Following the complete microstructural information from HE-SXRD, we used a suitably appropriate analytical model to predict the yield strength.

What sort of feedback did you receive regarding this work?

Initially critical from steel metallurgy experts, as this was a completely new finding. However, they finally appreciated this unique approach towards better steel design.

What are the next steps in this research?

We plan to generalize this concept to a variety of other complex steel and metal alloys such as carbon steel, high entropy alloy. Such tests with several batches of steel may be highly beneficial to various steel and metallurgy experts the faster way to design the high strength steel.

(1) S. Ghosh, S. Wang, H. Singh, G. King, Y. Xiong, T. Zhou, M. Huttula, J. Kömi, and W. Cao,

https://doi.org/10.1016/j.jmrt.2022.07.066

Harishchandra Singh is an Adjunct Professor at NANOMO, University of Oulu, Finland. His main research includes structural / building materials and energy production / storage materials with the goal to explain their physics via advanced synchrotron methods. Singh received Ph.D. in Physical Sciences from Raja Ramanna Centre for Advanced technology, India on synchrotron-based structural and spectroscopic studies. After Ph.D., Singh joined Stony Brook University/Brookhaven National laboratory, USA as a postdoctoral researcher for the successful development of modulation excitation X-ray absorption Spectroscopy at ISS beamline of NSLS-II synchrotron source.

Graham King received his B.S. in Chemistry from SUNY Buffalo in 2005 and his PhD in inorganic solid state chemistry from The Ohio State University in 2010 under the guidance of Patrick Woodward. He then spent 6 years at the Lujan Neutron Scattering Center at Los Alamos National Lab, first as a postdoc and then as a staff scientist. After briefly working as an independent consultant he came to CLS in 2018 as an instrument scientist for the Brockhouse Beamlines. He specializes in advanced powder diffraction methods for determination of the crystal and local structures of materials, with a special interest in cation ordered perovskites.

Articles

Harishchandra Singh, Graham King and associates have employed high energy synchrotron X-ray diffraction (HE-SXRD) experiments and an analytical model in order to predict the yield strength of cerium-modified super duplex stainless steel (SDSS) subjected to various cold- and cryo-deformation. Spectroscopy recently had the opportunity to discuss the experiments and the findings with Singh and King.

Quantitative Prediction of Yield Strength of Highly Alloyed Complex Steel Using High Energy Synchrotron X-Ray Diffractometry

The Eastern Analytical Symposium (EAS) supports a Student Research Awards program to recognize students involved in research in the broad field of analytical chemistry. 

These awards have been expanded to include both graduate and undergraduate students. This year, there are four winners in each category.

Left to right: Kaylie Kirkwood, Kevan Knizner, Samuel Krug, and Lexi McCarthy

The 2022 Graduate Student Research Awardees are Kaylie Kirkwood of North Carolina State University (Nominated by Prof. Erin Baker); Kevan Knizner of North Carolina State University (nominated by Prof. David Muddiman); Samuel Krug of the University of Maryland (nominated by Prof. Maureen Kane); and Lexi McCarthy of The Ohio State University (nominated by Prof. Phillip Grandinetti).

Left to right: Quang Minh (Harry) Dang, Olivia Dioli, Matthew Giammar, and Naiara Munich

The winners of the 2022 Undergraduate Student Research Award are Quang Minh (Harry) Dang of the University of Richmond (nominated by Prof. Michael Leopold); Olivia Dioli of North Carolina State University (nominated by Prof. David Muddiman); Matthew Giammar of The Ohio State University (nominated by Prof. Philip Grandinetti); and Naiara Munich of Barnard College (nominated by Prof. Lauren Marbella).

Nomination criteria for the awards include excellent grades, appraisals of how the students handle their investigations, their approach, and how they resolve problems and publicly disseminate their work. For more information on nominating a student for 2022, 

Student Research Awards to be Presented at EAS 2022

Physical biologist Manu Prakash received the New York Microscopical Society Ernst Abbe Award at an awards session at the Eastern Analytical Symposium (EAS) on Monday, November 14, in Plainsboro, New Jersey. The award celebrates of Prakash’s contributions to the field of microscopy, particularly through his development of the Foldscope, an optical microscope made from simple components, including a sheet of paper and a lens, that costs less than $1 to build.

Prakash’s Foldscope was designed to be portable and durable while performing on par with conventional research microscopes (140X magnification and 2-micrometer resolution). As part of the “frugal science” movement, the Foldscope enables communities around world to experience the world of microscopy.

Prakash uses his expertise in soft-matter physics to illuminate often easy-to-observe but hard-to explain phenomena in biological and physical contexts and to invent solutions to difficult problems in global health, science education, and ecological surveillance. His many lines of research are driven by curiosity about the diversity of life forms on our planet and how they work, empathy for problems in resource-poor settings, and a deep interest in democratizing the experience and joy of science globally.

Working on frugal science in his laboratory, Prakash builds, designs, and deploys tools for scientific explorations globally. His work in frugal science covers disciplines with applications in global health, environmental monitoring, and biodiversity discovery. The laboratory works in an open-source framework, where much of the work in frugal science is rapidly available to communities around the world, and consequently can be scaled.

Physical biologist Manu Prakash received the New York Microscopical Society Ernst Abbe Award at an awards session at the Eastern Analytical Symposium (EAS) on Monday, November 14, in Plainsboro, New Jersey. 

Manu Prakash 2022 wins New York Microscopical Society Ernst Abbe Award

Rohit Bhargava, a Founder and Professor of Bioengineering at the University of Illinois Urbana-Champaign, received the 2022 NY/NJ Section of the Society for Applied Spectroscopy Gold Medal Award on Wednesday, November 16, in an award session at the Eastern Analytical Symposium (EAS) in Plainsboro, New Jersey.

Bhargava received a B. Tech. dual degree in Chemical Engineering and Polymer Science from the Indian Institute of Technology, in New Delhi, and his PhD in Macromolecular Science and Engineering from Case Western Reserve University under Prof. Jack L. Koenig, developing infrared (IR) imaging techniques applied to polymer composites. Following his PhD, Bhargava was a Research Fellow at the National Institutes of Health with Ira W. Levin, developing IR imaging tools for molecular digital pathology. Bhargava joined the University of Illinois in 2005.

At the Cancer Center at Illinois at the University of Illinois, Bhargava runs the Chemical Imaging and Structures Laboratory. His research team has performed large-scale studies on prostate, breast, colon, brain, and skin tissue samples. His laboratory also focuses on fundamental science by developing optical theory for spectroscopy, where his team has created cell culture methods for 3D tumor mimicking systems—building a 3D printer to develop biomedical scaffolds and engineering cancer models. Instruments developed in the laboratory have been used to provide new means to characterize and define cancer using chemical imaging that is leading to the emergence of the field of digital molecular pathology. Using 3D printing and engineered tumor models, his most recent research seeks to create designer cancers in the laboratory.

Bhargava’s research in optical theory and numerical methods formed the theoretical foundation of IR imaging, leading to new instrumentation and technologies. He expanded the field of high-performance IR imaging, using it for pathology, and led the first large-scale validation of spectroscopic imaging for prostate cancer pathology, which is often cited as the gold standard protocol in the field.

Bhargava’s current research interests include developing IR chemical imaging, high quality tissue classification using artificial intelligence methods including deep learning, nanoscale IR chemical imaging, and applications in cancer pathology. He has authored and co-authored more than 200 publications and book chapters. His research has been recognized by several national and international awards including the Pittsburgh Spectroscopy Award (2022), Ellis R. Lippincott Award, Optica, Coblentz Society, and Society for Applied Spectroscopy (2021), Fellow, American Association for the Advancement of Science (2020), Beckman Vision and Spirit Award (2017), Agilent Thought Leader Award (2016), Fellow, American Institute for Medical and Biological Engineering (2015), Fellow, Society for Applied Spectroscopy (2015), William F. Meggers Award, Society for Applied Spectroscopy (2014), Craver Award (2013), and FACSS Innovation Award (2012).

Rohit Bhargava Receives 2022 NY/NJ Section of the Society for Applied Spectroscopy Gold Medal Award

The Emerging Leader in Atomic Spectroscopy Award recognizes the achievements and aspirations of a talented young atomic spectroscopist who has made strides early in his or her career toward the advancement of atomic spectroscopy techniques and applications.

The award will be given to a researcher who has focused the majority of his or her work in the field of analytical atomic spectroscopy, with direct contributions to inorganic mass spectrometry (MS), optical emission spectroscopy (OES), laser-induced breakdown spectroscopy (LIBS), atomic absorption spectroscopy (AAS), atomic fluorescence spectroscopy (AFS), and/or X-ray techniques through original research on the development or advancement of theory, instrumentation, measurement techniques, or applications.

The winner must be within 10 years of receiving his or her PhD in the year the award is granted. The winner is chosen by an independent scientific committee.

To nominate a candidate, please e-mail the following documents to Laura Bush, the editorial director of 

Information about the person submitting the nomination:

Year PhD was earned and from where (list degree, year, institution, and location). 

Important: Candidates must be within 10 years of receiving their PhD in the year the award is granted.

Short summary, in 100–200 words, of the candidate’s achievements or contributions (more details can follow in the sections below).

Please list the candidate’s five most important pieces of work (such as papers in peer-reviewed journals, technical reports written for an industrial community, or other) and explain briefly the significance of each.

Other key contributions to the field of atomic spectroscopy not captured above

Number of oral and poster presentations at scientific conferences

Service provided to the scientific community, such as volunteer work in scientific societies, work as a journal reviewer, and so on

Please include one seconding letter (letter of support) from a member of the atomic spectroscopy community (this person must be different from the nominator). The nominator may also provide an additional letter of support if desired.

Please provide a current resume or CV of the candidate in a Word or PDF file.

Include a high-resolution headshot of the nominee in a .jpg format.

The nomination form can be downloaded from this

Questions about the submission process should be directed to Laura Bush, the editorial director of 

Nominate a colleague for the 2024 Emerging Leader in Atomic Spectroscopy Award!

Call for Nominations: The 2024 Emerging Leader in Atomic Spectroscopy Award

Philip J. Grandinetti of the Ohio State University is the winner of the 2022 Eastern Analytical Symposium (EAS) Award for Outstanding Achievements in Magnetic Resonance. He received the award on Monday, November 14, in a session in his honor at EAS in Plainsboro, New Jersey.

Grandinetti studied for his PhD in physical chemistry at the University of Illinois, Urbana-Champaign, under Prof. Jiri Jonas, where he developed and applied in situ high-pressure nuclear magnetic resonance (NMR) methodologies to study the dynamics of elastohydrodynamic lubricants and pressure-induced phase transitions in lipids. After completing his PhD, Grandinetti worked at the University of California, Berkeley, in the laboratory of Prof. Alex Pines, from 1989 to 1993. While there, he made contributions to a new class of solid-state NMR methods for obtaining high-resolution spectra of half-integer quadrupolar nuclei.

Grandinetti’s current research interests focus on magnetic resonance to probe dynamics and structure in disordered and heterogeneous materials. He received an NSF CAREER award in 1995 and an NSF Creativity Award in 2004. He was a visiting professor at the Ecole Normale Supérieure de Lyon in 1999, a visiting professor and Le Studium Researcher at the CNRS in Orléans, France, in 2005-2006, the Allan Cox visiting professor in the School of Earth Sciences at Stanford University in 2009, and a visiting professor at the École Polytechnique Fédérale de Lausanne, Switzerland. He served on the editorial board of the journal 

 and was a council member of the International Society of Magnetic Resonance.

Each year, the Eastern Analytical Symposium honors analytical chemists who have distinguished career achievements. The recipients of these awards advanced these fields by superior work in developing theory, techniques, or instrumentation.

Philip J. Grandinetti of the Ohio State University is the winner of the 2022 Eastern Analytical Symposium (EAS) Award for Outstanding Achievements in Magnetic Resonance. 

Philip J. Grandinetti Receives 2022 EAS Award for Outstanding Achievements in Magnetic Resonance

Richard Crocombe of Crocombe Spectroscopy Consulting has won the 2022 Eastern Analytical Symposium (EAS) Award for Outstanding Achievements in Vibrational Spectroscopy. He was presented with the award on Tuesday, November 15, in an award session at EAS in Plainsboro, New Jersey.

Crocombe graduated from Oxford University with a BA and MA in chemistry, and the University of Southampton with a PhD in chemistry and spectroscopy. His thesis work involved classical infrared and Raman spectroscopy studies of small inorganic molecules, including matrix-isolation and isotopic substitution. A postdoctoral fellowship in the United States had Crocombe working on early applications of Fourier transform IR (FT-IR), including time-resolved spectroscopy and gas chromatography–IR (GC-IR), and infrared laser photolysis.

Crocombe joined Digilab (Bio-Rad) to work on laboratory FT-IR instrumentation. He held numerous positions at Digilab over the years, but concentrated on product, software, and applications development, including step-scan FT-IR applications, and spectroscopic imaging using two-dimensional focal plane array detectors. Later, he held positions at Axsun Technologies, Thermo Fisher Scientific, and finally PerkinElmer, concentrating on miniature, portable and handheld spectroscopic instruments, their development and applications. These spanned the range from near-infrared spectroscopy, X-ray fluorescence spectroscopy, Raman spectroscopy, and FT-IR spectroscopy to gas chromatography–mass spectrometry. In 2017 he left the corporate world to set up his own consulting company, helping to commercialize new miniature spectroscopic technologies.

He has been a co-chair of SPIE’s Next-Generation Spectroscopic Technologies conference for more than 10 years and is an SPIE Senior Member.He was selected for the Williams-Wright Award for Industrial Spectroscopy in 2012, is a Fellow of the Society for Applied Spectroscopy (SAS), and was President of SAS in 2020.

Crocombe has published extensively on the technologies and applications for miniature and portable spectrometers. He, Pauline Leary, and Brooke Kammrath are the joint editors of the two-volume book, 

Richard Crocombe of Crocombe Spectroscopy Consulting has won the 2022 Eastern Analytical Symposium (EAS) Award for Outstanding Achievements in Vibrational Spectroscopy. 

Richard Crocombe Receives 2022 EAS Award for Outstanding Achievements in Vibrational Spectroscopy

In the treatment of tuberculosis (TB), a contagious disease that causes 1.5 million deaths per year globally, early diagnosis is critical in order to control its spread. Unfortunately, standard tuberculosis diagnostic tests, such as sputum culture, can take days to weeks to yield results. In a recent paper, Ubaid Ullah of the Syed Babar Ali School of Science and Engineering in Pakistan and his colleaguesdemonstrate a quick, portable, easy-to-use, and non-invasive optical sensor based on sputum samples for tuberculosis detection using Raman spectroscopy to detect TB in a patient’s sputum supernatant. Ullah spoke to 

Your paper (1) demonstrates a quick, portable, easy-to-use, and non-invasive optical sensor for analysis of sputum samples for tuberculosis (TB) detection. What inspired the development of this sensor?

The current gold standard and most common practice test for TB diagnosis is the sputum culture, specifically in third-world countries where TB has a high impact. However, these tests take days to weeks to produce results. Meanwhile, the potential TB patient is out in the general public, probably infecting more and more people. Therefore, we devised an alternate approach that still makes use of the standard TB lab equipment and testing procedures, and yields findings within a couple of minutes. The catch is that we replace the time-consuming incubation step (where bacteria in TB liquid samples are nourished to form visible colonies) by exploiting spectroscopic information from the freshly prepared TB sample.

The probe uses Raman spectroscopy to evaluate detection of TB in a patient’s sputum supernatant. What advantages did Raman spectroscopy offer that other techniques available may have lacked?

Multiple techniques, including immune-chromatography, polymerase-chain-reaction (PCR), piezoelectricity, electrochemical, and surface plasmon resonance, have been implemented for TB detection. These methods, however, either have poor sensitivity and specificity, high operational cost, lack portability, invasiveness, or produce harmful byproducts. Raman spectroscopy, on the other hand, does not suffer from these limitations, and has been successfully applied to the diagnosis of various diseases, as evident from the fact that it has been used in clinical trials involving hundreds of patients to detect various types of cancer. In fact, companies now exist that provide commercial Raman systems for various disease diagnoses. For example, Kaiser Optical Systems, Inc. develops Raman systems for multiple applications, including cancer, skin, bone, eyes, and dental diagnosis.

How did you select the calibration set of samples and the validation set of samples? Were different samples used to develop the discriminant model versus samples used to test the model?

We employed principal component analysis (PCA) for the classification. Since PCA relies on dimensional reductionality, it bypasses the usual classification procedures of training and validation. We ran PCA on 112 patients’ data, and chose the first two orthogonal principal components, PC1 and PC2, for segregation.

Your paper states that the red and black dots are underneath the blue line—did you mean to say green and black dots, indicating the TB + samples are separated out from the red TB – samples?

Yes, the blue line serves as the classifier. As mentioned in Figure 3, the black and green dots below the blue line represent TB + patients on medication and recently diagnosed TB + patients, while red dots above the blue line denote TB – patients.

Briefly describe your discovery and development process.

Modern, sophisticated machine learning algorithms make it possible to detect very minute variations that were previously impossible to comprehend with conventional methods. It is well-researched that the sputum of a person with TB has a range of biomarkers, including esters and proteins. We hypothesize that the presence of these compounds minutely changes the Raman signature of the sputum’s supernatant sample, even after filtering mycobacterium tuberculosis (Mtb) bacteria cells. The change in the Raman signature is too weak to identify TB biomarkers, but is sufficient to probe TB. However, its weak nature makes it hard to differentiate the probe signal visually. Therefore, we utilized a machine learning algorithm, principal component analysis (PCA) for the classification.

The following is a brief description of the development process. We collected sputum from a potential TB patient, and prepared the sample following the standard TB culture protocol. Samples were then filtered to remove Mtb bacteria into a clean cuvette. Following this, we record Raman data of the cell-free sample supernatant using a wavelength and intensity calibrated diffraction limited spectrometer by averaging five frames of the Raman spectrum and subtracting the reference background spectrum. Each Raman spectrum was integrated for 1.5 min. The obtained Raman data was then regularized, a covariance matrix was found, principal components analysis was performed, and the sample data was plotted in the plane of the highest variance orthogonal components (PC1, PC2).

How does this work differ from what has been previously done by yourself or others?

As stated earlier, Raman spectroscopy has been successfully applied to detect various diseases, including cancer and skin diseases, and companies now exist that provide commercial Raman systems for various disease diagnoses. However, Raman spectroscopy is not widely exploited for TB detection, since it is predominantly a problem of developing countries. Researchers have utilized Raman spectroscopy to detect TB in blood and TB meningitis in cerebrospinal fluid (2,3). Even though these approaches accelerate TB diagnosis, their invasive nature limits its applications. A subsequent study that employed Raman spectroscopy of individual mycobacterium cells for TB detection offered even species-level information (4). Moreover, they achieved an accuracy of 94%. However, the complex sample preparation process necessitates the need for a specialist. Furthermore, human sampling was missing in the study. Here, for the first time, we utilize Raman spectroscopy and a machine learning algorithm to detect TB in sputum supernatant. The probe produces quick results, does not require trained laboratory personnel, is non-invasive in nature, and will use the already established state-of-the-art TB test facilities.

We demonstrate for the first time the application of Raman spectroscopy toward rapid TB detection using sputum samples. The sensor offers 100% true-positive and 93.3% true-negative accuracy after testing 112 TB patients. Significantly, our probe can provide a quick (few minutes) TB test result of an already processed sputum sample for the culture test. The probe can be easily integrated into conventional TB diagnostic labs where smear microscopy and culture tests are routinely conducted.

Were there any particular limitations or challenges you encountered in your work?

One particular limitation of our setup is its high capital cost, mainly due to the Raman spectrometer. Yes, working and gathering TB samples during the Covid pandemic was a huge challenge for us.

Can you please summarize the feedback that you have received from others regarding this work?

In addition to applause and greetings, we were advised to apply this technique to other infectious diseases such as malaria and pneumonia. Furthermore, it was suggested that we make a stand-alone commercial device out of this work.

We are looking for further funding to make this probe more robust, reduce its capital cost, and to make feasible the replacement of the standard TB culture test with a low-cost setup.

Do you think this work be taken into clinical trials for use in diagnostics?

Yes, this work has the capability to be taken into clinical trials for use in diagnostics.

U. Ullah, Z. Tahir, O. Qazi, S. Mirza, and M.I. Cheema, 

S. Khan, R. Ullah, S. Shahzad, N. Anbreen, M. Bilal, and A. Khan, 

R. Sathyavathi, N. C. Dingari, I. Barman, P. S. R. Prasad, S. Prabhakar, D. N. Rao, R. R. Dasari, and J. Undamatla, 

S. Stöckel, S. Meisel, B. Lorenz, S. Kloß, S. Henk, S. Dees, E. Richter,S. Andres, M. Merker, I. Labugger, and P. Rösch, 

 received his BS degrees in Electronics from the University of Peshawar in 2014, M.Phil. and PhD degrees in Electronics and Electrical Engineering from Quaid-i-Azam University (Islamabad, Pakistan) and Lahore University of Management Science (Lahore, Pakistan) in 2016 and 2021, respectively. He is currently working as a Postdoctoral Researcher in the Bio-Agri-Photonics Lab at Lahore University of Management Sciences. His research interests include the design and development of optical sensors for biomedical and chemical applications.

In the treatment of tuberculosis (TB), a contagious disease that causes 1.5 million deaths per year globally, early diagnosis is critical in order to control its spread. Unfortunately, standard tuberculosis diagnostic tests, such as sputum culture, can take days to weeks to yield results. In a recent paper, Ubaid Ullah of the Syed Babar Ali School of Science and Engineering in Pakistan and his colleagues demonstrate a quick, portable, easy-to-use, and non-invasive optical sensor based on sputum samples for tuberculosis detection using Raman spectroscopy to detect TB in a patient’s sputum supernatant. Ullah spoke to Spectroscopy about this sensor and its development.

Raman Spectroscopy and Machine Learning-Based Optical Probe for Tuberculosis Diagnosis via Sputum 

This article gives a brief overview of the major portable techniques: those based on optical spectroscopy techniques, including near-infrared (NIR), mid-infrared (mid-IR), and Raman spectroscopy; mass spectrometry (MS) systems, including high-pressure MS (HPMS), gas chromatography–MS (GC–MS), ion mobility spectrometry (IMS); elemental techniques, such as X-ray fluorescence (XRF) and laser-induced breakdown spectroscopy (LIBS); and emerging miniaturized techniques like nuclear magnetic resonance (NMR). The above are all “conventional” spectroscopic techniques and reduced to a rugged portable format, containing self-contained data systems. They provide specific and actionable information to their operators working with them outside the laboratory—in the field—and these instruments have well-defined value propositions. A recent development is the availability of low cost (<$100) multispectral sensors operating in the visible and NIR regions. This low cost enables the sensors to be embedded into consumer products, such as smart “white goods” appliances, personal care, fitness products, and even “wearables” products. In the future, miniature and portable spectrometers will be ubiquitous—outside the laboratory, and in your home and pocket.

In Chapter 1 of “Alice in Wonderland,” Alice chases the white rabbit down a hole and looks into a small passage, seeing “the loveliest garden you ever saw” (1). She can’t go through the passage until she imbibes from a bottle labeled “Drink Me” and shrinks in size. Although she shrinks in size, she does maintain all her faculties. Like Alice, spectrometers have gone through this miniaturization process while maintaining their functionalities. In the past 20 years, spectrometers have shrunk dramatically in size, giving us first laboratory-portable, toaster-sized instruments, then cordless drill-sized portable instruments for use in the field, and finally spectrometers the size of a computer mouse or a deck of cards (2). This shrinking has been achieved with only modest performance reductions in sampling versatility, spectral range, spectral resolution, and signal-to-noise (S/N). However, by utilizing the ever-increasing power of consumer electronics, these instruments are capable of generating reliable and actionable results in the field. The latest development is the availability of very low-cost multispectral sensors that are the size of a computer chip, leading to the possibility of embedding them into consumer goods.

It is convenient to classify portable spectrometers into four types (Table I). In this article, we are concerned with just the first two—completely integrated instruments, and miniature spectrometers or multispectral sensors, designed to be embedded in consumer goods.

We can see four portable spectrometer techniques: optical molecular analysis (UV-visible [UV-vis], near-infrared [NIR], mid-IR, and Raman); mass spectrometry (MS; high pressure mass spectrometry [HPMS], gas chromatography–mass spectrometry [GC–MS], and ion mobility spectroscopy [IMS]), and elemental analysis (X-ray fluorescence [XRF] and laser-induced breakdown spectroscopy [LIBS]). Relative newcomers are ruggedized and field-portable nuclear magnetic resonance (NMR), both chemical shift and time-domain (relaxometry) variants. Each technique or instrument has its own benefits and limitations, so we have to choose the right technique for the problem at hand, and Table II shows some of their established applications.

Optical molecular instruments are widely used for the rapid identification or confirmation of chemical substances, often “white powders.” These applications can range from confirming incoming material in pharmaceutical manufacturing (3), detecting counterfeit pharmaceuticals in the field, and identifying suspicious materials by the police, customs, border officials, and airport security personnel. NIR, mid-IR, and Raman spectrometers are all used in these areas, but each has its strengths and weaknesses (3). Briefly, Raman spectroscopy is often preferred because of its “point-and-shoot” ability, whereas mid-IR typically requires the material to be handled. This drawback of mid-IR tends to outweigh the issue of fluorescence in Raman spectra. NIR spectroscopy has been used for many years for the quantitative analysis of natural products (grain, fruits, and so on), and it is well-suited to these highly heterogeneous materials. Raman and NIR spectroscopy are direct competitors in many pharmaceutical applications (3).

These optical techniques are limited to major component (percent level) analyses in condensed phases. For trace analysis and complex-mixture analysis, mass spectrometric (MS) techniques are required. MS has typically required the use of a high vacuum, and this precluded miniaturization of the instrument to a handheld format. Briefcase-sized gas chromatography–mass spectrometry (GC–MS) instruments have been commercially available since approximately 1996. They are widely used by hazardous material technicians, the military, and environmental scientists to investigate and characterize suspicious locales. Because these instruments use a separations front end, they are excellent for analyzing complex mixtures and detecting trace components within those samples. HPMS operates at a modest vacuum (0.1 atmospheres) using an array of micro-ion traps and is therefore available in a handheld format. HPMS is fast (seconds), reliable for programmed target chemicals, and provides a presumptive method for identification. IMS has been used in airport security applications since the late 1980s, with operators “swabbing” luggage and analyzing that swap in a small desktop instrument. Portable versions are available in a “dustbuster” format, and wearable versions are employed by the military.

Portable XRF has been used for at least 20 years in the lifecycle of metal, from mineral prospecting, mining, refining, raw material confirmation, in-process inspection, and finally, to scrap metal sorting. Other applications include detection of heavy metals (such as lead) in old house paint and imported toys, recycling automotive catalytic converters, the “cash for gold” business, environmental surveys, and cultural heritage studies. For fundamental physical reasons, portable XRF has some limitations for elements lighter that silicon, and portable LIBS is especially useful there; for instance, portable LIBS has been used in aluminum alloy sorting and lithium applications, as well as for ferrous alloy identification.

NMR instruments fall into two broad classes: chemical shift and time domain, or relaxometry. Benchtop relaxometers were developed around the same time as analytical NIR instruments and serve some of the same applications, such as moisture measurement. Advances in permanent magnet technology and cell phone electronics enable relaxometry to be offered in a handheld format (4). Benchtop chemical-shift NMR instruments are available from a number of vendors, some with simple functionality and some capable of advanced pulse sequences. Although most of these instruments utilize the familiar 5-mm diameter NMR tubes, the technology can be adapted to wider bore, flowthrough plastic tubing, which is more rugged and suitable for quality assurance (QA) and quality control (QC) applications (5).

The value proposition for portable spectroscopy is summarized in Figure 1. In many cases, a spectrometer taken to the sample will generate instant actionable information that can determine your next step. That next step might be accepting or rejecting incoming raw material; identifying a spill and determining how to handle it; analyzing a suspicious white powder and generating probable cause for arrest, or how to treat an overdose subject; determining the value of scrap metal; or deciding where to drill or mine next. The time saved in achieving these answers is valuable in all these scenarios.

FIGURE 1: The value of a portable spectrometer—taking the spectrometer to the sample and to the point of need.

Although portable and handheld spectrometers are physically smaller than their laboratory counterparts, they typically include many features that permit their use in the field. Table III summarizes these ideal features, and we should note that many portable instruments incorporate most of them depending on the technology and application. The ability to “point-and-shoot” is particularly important because this eliminates the need for sample handling, cuvettes, and reagents, which could be problematic in the field. Any field instrument needs to be splash- and dust-proof, be shock- and drop-resistant, operate reliably over wide range of temperatures and humidity, and so on. The ability to communicate results and spectra, with timestamps and geographical information, is important, and these data often need to be uneditable or unalterable for compliance and legal reasons.

The ability to generate those actionable answers depends on turning a spectrum or spectra into information, which could be identities or concentrations. Therefore, applications development and incorporating the resulting databases or calibrations, as well employing appropriate algorithms, is key to the success of these portable instruments. It has been observed that applications (user requirements) drive the development of these instruments, and in turn, the availability of portable instrumentation drives the development of new applications. This virtuous cyclic process is illustrated in Figure 2. It should be noted that qualitative applications (identification) are significantly easier to develop than quantitative applications (concentrations of each component present), and less sensitive to small variations in spectral quality (S/N, wavelength scale shifts, fluorescence, and so on).

FIGURE 2: Applications development for portable spectrometers (Reproduced with permission from John Wiley from Chapter 1 in 

, R.A. Crocombe, P.E. Leary and B.W. Kammrath (editors), John Wiley, Chichester and Hoboken, 2021).

Commercially available portable spectrometers, operating in the visible-NIR region have been surveyed recently (6), and research on “photonic,” “plasmonic,” and “computational” devices was also reviewed (7). Further miniaturization may also be possible via metamaterials and photonic integrated circuits, with developments to extend operation into the mid-IR (8).

The lowest cost devices, available for a few dollars each, are multispectral sensors (as opposed to full spectrometers), with a small number (usually 6–16) of discrete detectors each having a different thin-film bandpass filter or implemented via organic semiconductors (9–13). A selection of these is shown in Figure 3. Some of these have been demonstrated for use in conventional applications, like illicit drug detection (14), but given their very small size and low cost, the large potential is for their use in embedded applications, with an eventual goal of being incorporated into “wearables” like smartwatches and smartphones.

FIGURE 3: Examples of miniature multispectral sensors. Their small size and low cost enables them to be incorporated into consumer products. Clockwise from top left: (a) a 14-channel visible region spectral sensor; (b) a 16-channel sensor based on an array of detectors having selective wavelengths in the 850-1700 nm range; (c) a new-generation lead salt array detector, covering a wavelength range of 1-3 μm; and (d) an OEM module with 16 near-infrared channels in the 1200–1700 nm range.

As noted above, turning spectra into information is key. In the case of embedded instruments, the application is presumably well-defined and limited in scope, and the probability of success is therefore high, even with a limited resolution multispectral sensor. Some existing products with photonic devices or spectral sensors include high-end sport watches (15), a ring-sized sleep monitor (16), smart toothbrushes (17), hair analysis with custom formulations (18), a smart cosmetic applicator (19), and a vacuum cleaner equipped with a laser and particle counter (20). The latter isn’t something out of an Austin Powers movie but is a product from Dyson that tangentially illuminates the surface, highlighting dust and dander while giving the user a quantitative particle count.

A possible future application is a “smart toilet.” A 2020 paper in the scientific literature (21) discusses “easily deployable hardware and software for the long-term analysis of a user’s excreta through data collection and models of human health.” The Japanese company Toto has discussed this possibility for several years, proposing sensors embedded in the toilet seat to measure heartbeat, body fat, and so on, combined with sensors in the toilet bowl itself to check urine and stool (22). Following analysis of these date in the cloud, it is proposed that the customer could be provided with suggestions for diet, guidance for improving health, and so on. After the 2022 Consumer Electronics Show, there was a column in the Wall Street Journal entitled “The Bathroom of the Future is Here: From High-Tech Toilets to Self-Filling Tubs” (23), which describes these possibilities:

“The suggestion pops up on your phone in the produce section of the grocery store: ‘Your diet seems unbalanced.’ The recommended recipe is: ‘salmon or chicken avocado salad.’ A message from your nutritionist? Nope. Personal trainer? If only. In this vision of the future, it’s your toilet doing the talking. The Wellness Toilet concept that Toto presented at this year’s Consumer Electronics Show is a commode that doubles as a health-monitoring device.”

The author of this article, along with Pauline Leary and Brooke Kammrath, recently edited a two-volume book on portable spectroscopy and spectrometry (24–25). The interested reader is referred to that, as well as to the following papers in this issue, for authoritative reviews of the technologies, instrumentation, and applications.

Spectrometers have been shrinking over the years, from room-filling behemoths, to two-foot-square beige boxes, and now to being transportable within the laboratory. The last 20 years have seen further transitions to portable and handheld spectrometers, for use outside the laboratory, with some now not much larger than a pack of cards. The development of very compact and low-cost multispectral sensors is the latest stage in this journey, and it now permits spectrometers, spectral sensors, and other photonic devices to be completely outside the laboratory: embedded in consumer goods, eventually reaching smartphones as well as smart watches and other wearables. You will have spectral sensors in your home, and in your pocket, and they may also turn up in the most unlikely of places, for and example in smart toilets. But that’s another story (26).

In Figure 3, thank you to (a) ams, (b) MantiSpectra, (c) trinamiX, and (d) Senorics for permissions to reproduce the pictures. 

(12), 1701–1751 (2018). DOI: 10.1177/0003702818809719

(6) K. Beć, J. Grabska, H.W. Siesler, and C.W. Huck 

Wearable Health & Well-being Sensors Rely on Silicon Photonics and Aim for Consumer

https://www.vttresearch.com/en/news-and-ideas/wearable-health-well-being-sensors-rely-silicon-photonics-and-aim-consumer-and

(12) Trinamix, Mobile NIR Spectroscopy Solutions. 

https://trinamixsensing.com/nir-spectroscopy/mobile-nir-spectroscopy- solutions/

Imagine You Could Simply Point Your Smartphone Towards Your Skin and Learn About Your Hydration Level Right Away

https://trinamixsensing.com/news-events/blog/imagine-you-could-simply-point-your-smartphone-towards-your-skin-and-learn-about-your-hydration-level-right-away/

https://www.garmin.com/en-US/c/wearables-smartwatches/

https://shop.colgate.com/products/smart-electric-toothbrush#/

https://www.dyson.com/vacuum-cleaners/cordless/v15/detect/yellow-iron

How’s your health? Toto’s smart toilet will keep tabs for you.

https://asia.nikkei.com/Business/Health-Care/How-s-your-health-Toto-s-smart-toilet-will-keep-tabs-for-you

The Bathroom of the Future Is Here: From High-Tech Toilets to Self-Filling Tubs

https://www.wsj.com/articles/high-tech-bathroom-11642720799

(24) R.A. Crocombe, P.E. Leary and B.W. Kammrath, Eds., 

Portable Spectroscopy and Spectrometry: Technologies and Instrumentation

 (John Wiley, Chichester, United Kingdom, and Hoboken, NJ, 2021), vol. 1. DOI: 10.1002/9781119636489

(25) R.A. Crocombe, P.E. Leary and B.W. Kammrath, Eds., 

Portable Spectroscopy and Spectrometry, vol. 2

 (John Wiley, Chichester, United Kingdom and Hoboken, NJ, 2021) DOI: 

 heads Crocombe Spectroscopic Consulting in Winchester, Massachusetts. Direct correspondence to: 

In the past 20 years, spectrometers have shrunk dramatically in size, and this shrinking has been achieved with only modest performance reductions in sampling versatility, spectral range, spectral resolution, and signal-to-noise.

Spectrometers in Wonderland: Shrinking, Shrinking, Shrinking

Over the course of the 19th century, the former Cataract House Hotel of Niagara Falls, New York, became one of the largest hotels in the region while also serving as an important “station” on the Underground Railroad. A park now occupies the area covering its demolished ruins. Since 2017, archaeological excavations of the site have taken place, led by the Anthropology Department at SUNY Buffalo. Although much is known about the overall design of the Cataract House Hotel, a clearer understanding of its construction phases, as well as its role in the Underground Railroad, could be determined from spectroscopic analysis in tandem with ongoing archaeological investigations. In 2022, in situ data collection was performed on plaster walls at the excavation site using a portable X-ray fluorescence (pXRF) instrument. These elemental data were used in conjunction with archaeological information to form conclusions regarding different construction phases of the hotel. Samples of plaster walls were also collected for further ex situ analyses with pXRF and portable laser-induced breakdown spectroscopy (pLIBS) in a laboratory setting. Future work will include data collection and analysis by additional spectroscopic methods of other artifacts collected at the site, such as pigment samples removed from an unearthed stone step.

Archaeometry, the combination of archaeological knowledge and quantitative measurements, offers empirical information regarding material origin, time of use or construction, and artifact conservation (1,2). Spectroscopic techniques have been shown to be valuable for characterizing archaeological materials and may provide chemical data that can be used to determine the relative ages of those features (2). In particular, elemental composition has been useful for gauging similarities among man-made materials because the makeup of building materials often can be associated with a specific time period, raw material sources, or both (2). Two elemental analysis techniques that are well suited for the analysis of precious archaeological samples are X-ray fluorescence (XRF) and laser-induced breakdown spectroscopy (LIBS). In XRF analysis, a sample is bombarded by X-rays, and the inner electrons of elements in the sample are removed, allowing outer electrons to fill their empty spaces and causing energy to be released in the form of a fluorescent X-ray photons. The energy of the photon released during this process is characteristic of the element being interrogated. In LIBS, a high-energy laser is fired at a sample, a portion of which becomes ablated. At the same time, the energy density yields a high-temperature plasma, which atomizes and excites ablated material. As the elements decay to a lower energy state, light is emitted at wavelengths characteristic of the elements in the sample.

These methods are appropriate for this task because they are minimally or non-destructive in the case of portable LIBS (pLIBS) and portable XRF (pXRF), respectively. Furthermore, both are available as handheld instruments and provide spectral information in a matter of seconds. Although each technique has its unique drawbacks, when they are used in conjunction, many of these limitations are minimized. For instance, XRF provides qualitative and quantitative information for larger elements, whereas low-Z elements, such as carbon and lithium, are not detected. Meanwhile, LIBS is capable of measuring a wider range of elements, including light elements. The nature of the LIBS method also allows for faster data collection in much more focused areas; for LIBS instruments with automated two-dimensional (2D) elemental mapping modes, the technique can easily be applied for evaluating the homogeneity of a sample (3). However, the LIBS spectra are much more data-rich and with higher background than XRF spectra and require more analysis before the elements present can be identified and quantified. The LIBS method is also quasi-destructive. Depending on the intensity of the laser, the number of pulses used to generate a spectrum, and the type of material being ablated, LIBS leaves small, sometimes visible craters on the surface of a sample. The X-rays emitted in XRF leave no marks on any sample during data collection.

The development and proliferation of handheld chemical analysis instruments, such as XRF, LIBS, Raman spectroscopy, and infrared (IR) spectroscopy, has greatly expanded archaeometric capabilities: samples can be rapidly analyzed in situ where access can be sharply limited (4). Obtaining this information in the field allows conclusions to be made during an excavation and inform the direction of a project, such as taking additional samples or deciding where next to dig. This work describes the use of two spectroscopic techniques, XRF and LIBS, to analyze architectural features uncovered during the recent archaeological excavation of the Cataract House, which was once a spacious, luxury hotel that served as an important node on the Underground Railroad (5).

The Cataract House, located in Niagara Falls, New York, was built in 1825 and named for the nearby cataracts, or waterfalls. It began as a simple, three-story building, but by the mid-1840s, the Cataract House had undergone multiple expansions to become one of the largest hotels in the area (Figure 1) (6). The hotel drew tourists from across the United States, including slave-holding families from the southern United States, who were often accompanied by several enslaved persons (5).

FIGURE 1: Photograph of the Cataract House viewed from Goat Island in the Niagara River circa 1800s.

In the early 1840s, the Cataract House became the first hotel in Niagara Falls to employ African-Americans. Many of those hired were from southern states and may have been former slaves themselves (5). The hotel waitstaff made use of their positions as employees of the Cataract House and their proximity to Canada, where slavery had been abolished in 1834, to aid enslaved visitors in escaping to freedom (5). Their efforts resulted in several successful escapes, including in the cases of Cecelia Reynolds, Nancy Berry, and Patrick Sneed (5,7). Other less successful rescue attempts resulted in some negative press around the hotel, but the Underground Railroad “station” continued to operate out of the hotel through the end of the American Civil War in 1865 (5,7).

Between the 1890s and 1920s, the practice of hiring African-American waiters in American hotels and restaurants declined significantly, and the composition of the waitstaff at the Cataract House reflected this trend. The Cataract House continued operating as a hotel until 1945, when a fire destroyed the building (8,9). The ruined hotel was razed in 1946, with rubble from above-ground structures being used to fill in basements. Plans to rebuild were never realized and the site was covered. Today, Heritage Park occupies much of the former hotel’s location (8,9).

Recently, there has been renewed interest in the site, particularly with regard to the Underground Railroad activity. In 2015, preliminary work began to establish an excavation of the hotel (8,9). Digging started in 2017, and subsequent excavations were carried out in 2018 (7) and resumed in 2022. In 2017 and 2018, excavations took place along the former eastern wall of the hotel. In 2017, test units (TUs), which are one square meter trenches dug at areas of cultural interest and carefully documented, were dug, making up two larger trenches. Trench 1 contained TUs 1 and 2, Trench 2 contained TUs 3 and 4, and TU 5 was dug in a separate location (Figure 2). Both excavated trenches contained foundation-wall segments from the Cataract House, referred to as features, which are indicated in Figure 2. Feature 1 (Figure 3a), along the eastern side of Trench 1, is a semi-intact wall of an unknown substrate covered in plaster. Feature 2 (Figure 3b), on the northern side of Trench 2, is a semi-intact brick wall partially covered by a layer of plaster approximately 25 mm thick. In 2018, two additional trenches, Trench 3 containing TUs 6 and 7, and Trench 4 containing TUs 8 and 9, were dug and TU 10 was dug in a separate location (see Figure 2). These trenches lay to the east of the Cataract House’s easternmost wall. The spaces between these trenches and TU 5 were excavated, connecting them and turning TUs 5–9 into one large trench (8,9).

FIGURE 2: Field map of Test Unit (TU) 1–10 locations relative to Heritage Park landmarks. Each numbered TU is one square meter.

FIGURE 3: Photographs of Cataract House excavation sites of (a) Feature 1; (b) Feature 2; and (c) Feature 6 in May 2022.

In 2022, the focus of the excavations shifted toward the Cataract House’s kitchen, which is believed to have been the hub of local Underground Railroad activity. A new trench with four TUs (TUs 11–14) was dug several yards to the west of the original TUs. Site archaeologists used floor plans of the hotel to guide placement of the trench, approximating the location of the kitchen. Uncovered in this trench was Feature 6 (Figure 3c), an entryway flanked by plaster-covered wall remnants and lined on one side with wooden trim. To investigate the relative ages of these features and verify the accuracy of the hotel’s floor plan, atomic spectroscopic methods of analysis were employed.

In Summer 2022, a handheld XRF spectrometer was brought to the ongoing Cataract House excavation with the intention of determining whether construction features in separate trenches were of similar elemental composition and, therefore, likely built as part of the same expansion or modification. Because of the simplicity of the spectra produced and the possibility that the features being analyzed may be present in small quantities or considered precious, XRF was used for in situ data collection. Spectra were obtained with a Bruker Tracer III-V+ and fitted with a rhodium X-ray tube and a yellow filter with 305-μm aluminum and 25-μm titanium. The X-ray tube was operated at 40 keV of excitation energy and 3 μA of current. Each interrogate spot was analyzed with the head of the XRF instrument flush with the plaster surface for 120 s. Duplicate spectra were collected for select locations that were easily accessible based on geometric placement of the feature to be analyzed and instrument dimensions. The spectra were taken at points on the flattest parts of the plaster and were at least 15 cm apart from other points. A total of 39 spectra were obtained onsite from Features 1 and 6.

Excavation time constraints limited the number of sample spots and spectra obtained in situ. However, plaster wall samples were removed from Features 1, 2, and 6, and they were further analyzed in the laboratory. There were six samples collected from Feature 1, 11 samples collected from Feature 2, and seven samples collected from Feature 6. Additional pXRF data was collected with the same handheld XRF instrument and settings used for in situ analysis. For the laboratory measurements, the XRF instrument was mounted to a stand pointing upward and samples were placed on top of the device so that they were flush with its head. Replicate XRF spectra were obtained at every analyzed location.

To verify and support XRF results, pLIBS spectra were collected in the lab using the same set of samples from Features 1, 2, and 6. The pLIBS instrument used (the Z-300 LIBS Analyzer from SciAps) contained three charge-coupled device (CCD) spectrometers that together cover a wavelength range of 190–950 nm. The instrument utilizes an Nd:YAG laser at a wavelength of 1064 nm and a beam diameter of 100 μm. Spectra were obtained with a laser repetition rate of 50 Hz. Two cleaning shots and four data-collection shots were used to generate each spectrum. Additionally, argon gas (high purity grade from SciAps) was used to purge the sample area to increase the spectral intensity of most elemental lines; argon purge is an integrated feature of the instrument used for this study that delivers a few milliliters of gas per analysis. The samples were placed flush with the head of the instrument during analysis. Replicate analyses with LIBS were performed in certain locations to verify consistency in intensity and elements detected. These two instruments were used to collect data sets from the same set of samples from Features 1, 2, and 6. A total of 116 XRF and 60 LIBS spectra were collected in the laboratory, including replicate spectra.

Spectra taken in situ with pXRF were visually distinguishable by the intensity of the peaks. For example, spectra taken from the left side of Feature 1 had much more intense lead peaks than those taken from the right side. To demonstrate, a plot of overlayed spectra from both sides of Feature 1 is shown in Figure 4. For a more definitive conclusion regarding the elemental compositions of the plasters from the site, principal component analysis (PCA) was performed with Unscrambler (version 10.1 from AspenTech) on three data sets extracted from the Cataract House plaster sampling frame to compare the data from the different features; each is discussed below. Prior to principal component analysis (PCA), a subset of data was evaluated using a Shapiro-Wilkes test and was found to be normal.

FIGURE 4: Overlay of two XRF spectra collected in situ from different parts of Feature 1 showing dramatic differences in lead and zinc content.

XRF Data Extracted In Situ from Features 1 and 6

The XRF spectra from the in-field analysis was used for PCA analysis. This fully cross-validated PCA was performed at the site during the 2022 excavation season so that results could be quickly relayed to archaeologists. This initial PCA was produced using the XRF spectral intensity data that was mean centered for each analysis. Feature 1 was found to contain two different elemental compositions that were distinct from the single composition across Feature 6. Both features contained calcium, iron, zinc, lead, and strontium, though in different abundances. Feature 1 was found to be composed of two distinct regions, marked by different levels of lead, according to XRF spectra collected from various points on the feature (Figure 4). The left side of Feature 1 displayed higher amounts of lead than the right side of Feature 1 or any part of Feature 6. A thin, grayish coating—possibly paint—on the left side of Feature 1 may explain the higher lead levels. Lead was commonly used in paint formulations, with its use in the United States peaking in the 19th century. Because Feature 1 was a continuous piece of plaster, the higher lead composition on the left side is not indicative of a second construction event. Feature 6 has more strontium than Feature 1 and it is believed that Feature 6 was built earlier, a hypothesis supported by the floor plans and records available. At the site, the XRF analysis data corroborated the theory that Features 1 and 6 were built during separate construction events.

XRF Data Extracted In Situ Combined with XRF Data Extracted Ex Situ

Fully cross-validated PCA with XRF results verified that the in situ and ex situ data could be combined while also comparing the elemental compositions of Features 1, 2, and 6. The score plot from this PCA can be seen in Figure 5a. Integrated peak areas from the XRF spectra were used to generate this PCA and data were normalized to one, mean centered, and divided by the standard deviation of the data set. Elements included in the analysis included calcium, iron, nickel, lead, strontium, and zinc. Spectra taken from the high-lead portion of Feature 1 were excluded from this PCA because the high lead levels were found to be from paint (see above) and not part of the plaster composition. Sodium peaks, which are often inflated by soil contamination, were similarly excluded from the PCA. The explained variance of PCs 1 through 3 was 90.1%. The majority variance in PC1 was because of contributions from nickel, iron, and calcium. Meanwhile, zinc and lead contributed the most to variance in PC2 and iron and calcium to variance in PC3. This combined in situ and ex situ data analysis supports the earlier finding that Features 1 and 6 are made of different plasters. The XRF data collected ex situ also included Feature 2, which was not analyzed at the site. According to PCA results, Feature 2 has a third distinct plaster composition, containing more zinc than the other two features.

FIGURE 5: Three-dimensional PCA score plots for (a) in situ and ex situ XRF; and (b) ex situ LIBS from analyses of wall samples from Features 1 (blue squares), 2 (red circles), and 6 (green triangles).

LIBS Data Extracted Ex Situ from Features 1, 2, and 6 

The fully cross-validated PCA from the laboratory-based LIBS analysis corroborated the XRF results and further distinguished the features with a larger subset of elements detected by LIBS, which included nickel, carbon, magnesium, silicon, aluminum, lead, iron, calcium, strontium, barium, lithium, and potassium. Prior to PCA analysis, the data were normalized to one, mean centered, and divided by the standard deviation of the data set. This PCA was performed using integrated peaks at selected wavelengths, which are listed in Table I, with the score plot shown in Figure 5b. The explained variance across PCs 1–3 was 87.0%, where aluminum, strontium, silicon, carbon, and magnesium contributed the most to the variance in PC1. Variances for PC2 and PC3 was because of mainly barium, calcium, and potassium, respectively. As anticipated, analysis of these data revealed additional elements that could not be detected by XRF, providing information that may link the plasters to specific time periods. For example, carbon is identified in all three plasters, but almost twice as much carbon is present in Features 1 and 2 as in Feature 6. Calcium carbonate (CaCO

), or lime, was commonly used in North American plasters before the 20th century (10). These LIBS results also showed that Feature 6, in addition to high amounts of strontium, contained more lithium than either Feature 1 or 2 and revealed a higher degree of heterogeneity in Feature 2’s plaster than in Features 1 and 6, with Feature 2 being speckled with small, high-barium areas. However, the separation between Features 1 and 2 can be seen more clearly in the score plot of the XRF data. Overall, the LIBS and XRF results both demonstrated that Features 1 and 2 share many elemental components and are more similar to each other than either is to Feature 6, suggesting that Features 1 and 2 were built at approximately the same time.

Combining archaeological knowledge with empirical evidence established using analytical techniques, we have been able to distinguish features at the Cataract House excavation from one another and relate them to specific time periods. Through the application of handheld instruments for collecting and analyzing data in situ, archaeological endeavors can be supported by rapidly supplying information during an ongoing investigation. Such information may inform the direction of an excavation, enhancing or modifying conclusions based solely on a feature’s appearance and surroundings. Future work will focus on analysis of other, non-plaster artifacts recovered from the site, allowing archaeologists to confidently develop a clearer picture of the Cataract House during its time as a “station” on the Underground Railroad.

(2) M.K. Donais, S. Wojtas, A. Desmond, B. Duncan, and D.B. George, 

(3) R.S. Harmon, D. Khashchevskaya, M. Morency, L.A. Owen, M. Jennings, J.R. Knott, et al, 

Portable Spectroscopy and Spectrometry 2: Applications

, R. Crocombe, P. O’Leary, and B. Kammrath, Eds. (Wiley & Sons Ltd., West Sussex, United Kingdom, 2021), pp. 523–544.

(5) J. Wellman, “Niagara Falls Underground Railroad Heritage Area Management Plan, Appendix C: Survey of Sites Relating to the Underground Railroad, Abolitionism, and African American Life in Niagara Falls and Surrounding Area, 1820–1880”, for Companies and Niagara Falls Underground Railroad Heritage Area Commission, April 2012.

Descendants of John Whitney, Who Came from London, England, to Watertown, Massachusetts

(7) K. Whalen, R. Austin, N. Montague, and D.J. Perrelli, 

Famed Cataract House Turned Into Mass of Charred Ruins

(10) R.F. Austin, “Analysis of Wall Plasters at the Cataract House Site, City of Niagara Falls, Niagara County, New York”, State University of New York at Buffalo, 2022.

 are with the Department of Chemistry and Chemical Biology at Rensselaer Polytechnic Institute, in Troy, New York. 

 is with the Department of Anthropology, at the State University of New York at Buffalo, in Buffalo, New York. 

 is with the Chemistry Department at St. Anselm College, in Manchester, New Hampshire. Direct correspondence to: 

Portable X-ray fluorescence was used to analyze the archaeological remains of an Underground Railroad station to gain a clearer understanding of the construction phases it underwent during the 19th century.

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