Showing papers in "Applied Spectroscopy in 2016"

On-Chip Micro-Electro-Mechanical System Fourier Transform Infrared (MEMS FT-IR) Spectrometer-Based Gas Sensing

Abstract: In this work, we study the detection of acetylene (C2H2), carbon dioxide (CO2) and water vapor (H2O) gases in the near-infrared (NIR) range using an on-chip silicon micro-electro-mechanical system (MEMS) Fourier transform infrared (FT-IR) spectrometer in the wavelength range 1300-2500 nm (4000-7692 cm(-1)). The spectrometer core engine is a scanning Michelson interferometer micro-fabricated using a deep-etching technology producing self-aligned components. The light is free-space propagating in-plane with respect to the silicon chip substrate. The moving mirror of the interferometer is driven by a relatively large stroke electrostatic comb-drive actuator corresponding to about 30 cm(-1) resolution. Multi-mode optical fibers are used to connect light between the wideband light source, the interferometer, the 10 cm gas cell, and the optical detector. A wide dynamic range of gas concentration down to 2000 parts per million (ppm) in only 10 cm length gas cell is demonstrated. Extending the wavelength range to the mid-infrared (MIR) range up to 4200 nm (2380 cm(-1)) is also experimentally demonstrated, for the first time, using a bulk micro-machined on-chip MEMS FT-IR spectrometer. The obtained results open the door for an on-chip optical gas sensor for many applications including environmental sensing and industrial process control in the NIR/MIR spectral ranges.

Application of Raman Spectroscopy and Infrared Spectroscopy in the Identification of Breast Cancer

Abstract: Raman spectroscopy and infrared (IR) spectroscopy are both techniques that allow for the investigation of vibrating chemical particles. These techniques provide information not only about chemical particles through the identification of functional groups and spectral analysis of so-called "fingerprints", these methods allow for the qualitative and quantitative analyses of chemical substances in the sample. Both of these spectral techniques are frequently being used in biology and medicine in diagnosing illnesses and monitoring methods of therapy. The type of breast cancer found in woman is often a malignant tumor, causing 1.38 million new cases of breast cancer and 458 000 deaths in the world in 2013. The most important risk factors for breast cancer development are: sex, age, family history, specific benign breast conditions in the breast, ionizing radiation, and lifestyle. The main purpose of breast cancer screening tests is to establish early diagnostics and to apply proper treatment. Diagnoses of breast cancer are based on: (1) physical techniques (e.g., ultrasonography, mammography, elastography, magnetic resonance, positron emission tomography [PET]); (2) histopathological techniques; (3) biological techniques; and (4) optical techniques (e.g., photo acoustic imaging, fluorescence tomography). However, none of these techniques provides unique or especially revealing answers. The aim of our study is comparative spectroscopic measurements on patients with the following: normal non-cancerous breast tissue; breast cancer tissues before chemotherapy; breast cancer tissues after chemotherapy; and normal breast tissues received around the cancerous breast region. Spectra collected from breast cancer patients shows changes in amounts of carotenoids and fats. We also observed changes in carbohydrate and protein levels (e.g., lack of amino acids, changes in the concentration of amino acids, structural changes) in comparison with normal breast tissues. This fact verifies that Raman spectroscopy and IR spectroscopy are very useful diagnostic tools that will shed new light in understanding the etiology of breast cancer.

Mobile Spectroscopic Instrumentation in Archaeometry Research.

Abstract: Mobile instrumentation is of growing importance to archaeometry research. Equipment is utilized in the field or at museums, thus avoiding transportation or risk of damage to valuable artifacts. Many spectroscopic techniques are nondestructive and micro-destructive in nature, which preserves the cultural heritage objects themselves. This review includes over 160 references pertaining to the use of mobile spectroscopy for archaeometry. Following a discussion of terminology related to mobile instrumental methods, results of a literature survey on their applications for cultural heritage objects is presented. Sections devoted to specific techniques are then provided: Raman spectroscopy, X-ray fluorescence spectrometry, Fourier transform infrared spectroscopy, laser-induced breakdown spectroscopy, and less frequently used techniques. The review closes with a discussion of combined instrumental approaches.

Using Nondestructive Portable X-ray Fluorescence Spectrometers on Stone, Ceramics, Metals, and Other Materials in Museums: Advantages and Limitations

Abstract: Elemental analysis is a fundamental method of analysis on archaeological materials to address their overall composition or identify the source of their geological components, yet having access to instrumentation, its often destructive nature, and the time and cost of analyses have limited the number and/or size of archaeological artifacts tested. The development of portable X-ray fluorescence (pXRF) instruments over the past decade, however, has allowed nondestructive analyses to be conducted in museums around the world, on virtually any size artifact, producing data for up to several hundred samples per day. Major issues have been raised, however, about the sensitivity, precision, and accuracy of these devices, and the limitation of performing surface analysis on potentially heterogeneous objects. The advantages and limitations of pXRF are discussed here regarding archaeological studies of obsidian, ceramics, metals, bone, and painted materials.

A 100 kHz Time-Resolved Multiple-Probe Femtosecond to Second Infrared Absorption Spectrometer:

Abstract: We present a dual-amplifier laser system for time-resolved multiple-probe infrared (IR) spectroscopy based on the ytterbium potassium gadolinium tungstate (Yb:KGW) laser medium. Comparisons are made between the ytterbium-based technology and titanium sapphire laser systems for time-resolved IR spectroscopy measurements. The 100 kHz probing system provides new capability in time-resolved multiple-probe experiments, as more information is obtained from samples in a single experiment through multiple-probing. This method uses the high repetition-rate probe pulses to repeatedly measure spectra at 10 µs intervals following excitation allowing extended timescales to be measured routinely along with ultrafast data. Results are presented showing the measurement of molecular dynamics over >10 orders of magnitude in timescale, out to 20 ms, with an experimental time response of <200 fs. The power of multiple-probing is explored through principal component analysis of repeating probe measurements as a novel method for removing noise and measurement artifacts.

Raman Gas Analyzer (RGA): Natural Gas Measurements.

Abstract: In the present work, an improved model of the Raman gas analyzer (RGA) of natural gas (NG) developed by us is described together with its operating principle. The sensitivity has been improved and the number of measurable gases has been expanded. Results of its approbation on a real NG sample are presented for different measurement times. A comparison of the data obtained with the results of chromatographic analysis demonstrates their good agreement. The time stability of the results obtained using this model is analyzed. It is experimentally established that the given RGA can reliably determine the content of all molecular NG components whose content exceeds 0.005% for 100 s; moreover, in this case the limiting sensitivity for some NG components is equal to 0.002%.

Application of Handheld Laser-Induced Breakdown Spectroscopy (LIBS) to Geochemical Analysis.

Abstract: While laser-induced breakdown spectroscopy (LIBS) has been in use for decades, only within the last two years has technology progressed to the point of enabling true handheld, self-contained instruments. Several instruments are now commercially available with a range of capabilities and features. In this paper, the SciAps Z-500 handheld LIBS instrument functionality and sub-systems are reviewed. Several assayed geochemical sample sets, including igneous rocks and soils, are investigated. Calibration data are presented for multiple elements of interest along with examples of elemental mapping in heterogeneous samples. Sample preparation and the data collection method from multiple locations and data analysis are discussed.

Near-Infrared Grating Spectrometer for Mobile Phone Applications.

Abstract: Near-infrared (NIR) spectroscopy is a well-established technique for the chemical analysis of organic and inorganic matter Accordingly, spectroscopic instrumentation of different complexity has been developed and is currently commercially available However, there are an increasing number of new mobile applications that have come into focus and that cannot be addressed by the existing technology due to size and cost Therefore, a new miniaturized scanning grating spectrometer for NIR spectroscopy has been developed at Fraunhofer IPMS It is based on micro-electro-mechanical systems (MEMS) technology, and has been designed to meet the requirements for mobile application, regarding spectral range, resolution, overall size, robustness, and cost The MEMS spectrometer covers a spectral range from 950 nm to 1900 nm at a resolution of 10 nm The instrument is extremely small and has a volume of only 21 cm(3) Therefore, it is well suited for integration, even into a mobile phone A first sample of the new spectrometer has been manufactured and put into operation The results of a series of test measurements are in good agreement with the requirements and specifications

Forensic Hair Differentiation Using Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) Spectroscopy

Abstract: Hair and fibers are common forms of trace evidence found at crime scenes. The current methodology of microscopic examination of potential hair evidence is absent of statistical measures of performance, and examiner results for identification can be subjective. Here, attenuated total reflection (ATR) Fourier transform-infrared (FT-IR) spectroscopy was used to analyze synthetic fibers and natural hairs of human, cat, and dog origin. Chemometric analysis was used to differentiate hair spectra from the three different species, and to predict unknown hairs to their proper species class, with a high degree of certainty. A species-specific partial least squares discriminant analysis (PLSDA) model was constructed to discriminate human hair from cat and dog hairs. This model was successful in distinguishing between the three classes and, more importantly, all human samples were correctly predicted as human. An external validation resulted in zero false positive and false negative assignments for the human class. From a forensic perspective, this technique would be complementary to microscopic hair examination, and in no way replace it. As such, this methodology is able to provide a statistical measure of confidence to the identification of a sample of human, cat, and dog hair, which was called for in the 2009 National Academy of Sciences report. More importantly, this approach is non-destructive, rapid, can provide reliable results, and requires no sample preparation, making it of ample importance to the field of forensic science.

Mid-Infrared Waveguides: A Perspective:

Abstract: Significant advancements in waveguide technology in the mid-infrared (MIR) regime during recent decades have assisted in establishing MIR spectroscopic and sensing technologies as a routine tool among nondestructive analytical methods. In this review, the evolution of MIR waveguides along with state-of-the-art technologies facilitating next-generation MIR chem/bio sensors will be discussed introducing a classification scheme defining three “generations” of MIR waveguides: (1) conventional internal reflection elements as “first generation” waveguides; (2) MIR-transparent optical fibers as “second generation” waveguides; and most recently introduced(3) thin-film structures as “third generation” waveguides. Selected application examples for these each waveguide category along with future trends will highlight utility and perspectives for waveguide-based MIR spectroscopy and sensing systems.

Precise Determination of Brillouin Scattering Spectrum Using a Virtually Imaged Phase Array (VIPA) Spectrometer and Charge-Coupled Device (CCD) Camera.

Abstract: Brillouin spectroscopy is an emerging tool for microscopic optical imaging as it allows noninvasive assessment of viscoelastic properties of materials. The use of atomic–molecular absorption cells as ultra-narrow notch filters allows acquisition of Brillouin spectra from turbid samples despite their strong elastic scattering. However, such systems alter the shapes of the Brillouin lines, making the precise determination of the Brillouin shift difficult. In this report, we propose a simple method for analyzing the Brillouin spectrum using a customized least-square fitting algorithm. The absorption spectrum induced by the atomic–molecular cell was taken into consideration. The capability of the method is confirmed by processing experimental spectroscopic data from the pure water at different temperatures. The accuracy of the measurements of ±1 MHz spectral line shift is experimentally demonstrated.

Raman Spectroscopy an Option for the Early Detection of Citrus Huanglongbing

Abstract: This research describes the application of portable field Raman spectroscopy combined with a statistical analysis of the resulting spectra, employing principal component analysis (PCA) and linear discriminant analysis (LDA), in which we determine that this method provides a high degree of reliability in the early detection of Huanglongbing (HLB) on Sweet Orange, disease caused by the bacteria Candidatus Liberibacter asiaticus. Symptomatic and asymptomatic plant samples of Sweet Orange (Citrus sinensis), Persian Lime (C. latifolia), and Mexican Lime (C. aurantifolia) trees were collected from several municipalities, three at Colima State and three at Jalisco State (HLB presence). In addition, Sweet Orange samples were taken from two other Mexican municipalities, one at San Luis Potosi and the other at Veracruz (HLB absent). All samples were analyzed by real-time PCR to determine its phytosanitary condition, and its spectral signatures were obtained with an ID-Raman mini. Spectral anomalies in orange trees HLB-positive, were identified in bands related to carbohydrates (905 cm(-1), 1043 cm(-1), 1127 cm(-1), 1208 cm(-1), 1370 cm(-1), 1272 cm(-1), 1340 cm(-1), and 1260-1280 cm(-1)), amino acids, proteins (815 cm(-1), 830 cm(-1), 852 cm(-1), 918 cm(-1), 926 cm(-1), 970 cm(-1), 1002 cm(-1), 1053 cm(-1), and 1446 cm(-1)), and lipids (1734 cm(-1), 1736 cm(-1), 1738 cm(-1), 1745 cm(-1), and 1746 cm(-1)). Moreover, PCA-LDA showed a sensitivity of 86.9 % (percentage of positives, which are correctly identified), a specificity of 91.4 % (percentage of negatives, which are correctly identified), and a precision of 89.2 % (the proportion of all tests that are correct) in discriminating between orange plants HLB-positive and healthy plants. The Raman spectroscopy technique permitted rapid diagnoses, was low-cost, simple, and practical to administer, and produced immediate results. These are essential features for phytosanitary epidemiological surveillance activities that may conduct a targeted selection of highly suspicious trees to undergo molecular DNA analysis.

Development and Applications of Portable Gas Chromatography–Mass Spectrometry for Emergency Responders, the Military, and Law-Enforcement Organizations:

Abstract: Portable gas chromatography-mass spectrometry (GC-MS) systems are being deployed for field use, and are designed with this goal in mind. Performance characteristics of instruments that are successful in the field are different from those of equivalent technologies that are successful in a laboratory setting. These field-portable systems are extending the capabilities of the field user, providing investigative leads and confirmatory identifications in real time. Many different types of users benefit from the availability of this technology including emergency responders, the military, and law-enforcement organizations. This manuscript describes performance characteristics that are important for field-portable instruments, especially field-portable GC-MS systems, and demonstrates the value of this equipment to the disciplines of explosives investigations, fire investigations, and counterfeit-drug detection. This paper describes the current state of portable GC-MS technology, including a review of the development of portable GC-MS, as well as a demonstration of the value of this capability using different examples.

Random Forest (RF) Wrappers for Waveband Selection and Classification of Hyperspectral Data.

Abstract: Hyperspectral data collected using a field spectroradiometer was used to model asymptomatic stress in Pinus radiata and Pinus patula seedlings infected with the pathogen Fusarium circinatum. Spectral data were analyzed using the random forest algorithm. To improve the classification accuracy of the model, subsets of wavebands were selected using three feature selection algorithms: (1) Boruta; (2) recursive feature elimination (RFE); and (3) area under the receiver operating characteristic curve of the random forest (AUC-RF). Results highlighted the robustness of the above feature selection methods when used in conjunction with the random forest algorithm for analyzing hyperspectral data. Overall, the Boruta feature selection algorithm provided the best results. When discriminating F. circinatum stress in Pinus radiata seedlings, Boruta selected wavebands (n = 69) yielded the best overall classification accuracies (training error of 17.00%, independent test error of 17.00% and an AUC value of 0.91). Classification results were, however, significantly lower for P. patula seedlings, with a training error of 24.00%, independent test error of 38.00%, and an AUC value of 0.65. A hybrid selection method that utilizes combinations of wavebands selected from the three feature selection algorithms was also tested. The hybrid method showed an improvement in classification accuracies for P. patula, and no improvement for P. radiata. The results of this study provide impetus towards implementing a hyperspectral framework for detecting stress within nursery environments.

Portable Raman, DRIFTS, and XRF Analysis to Diagnose the Conservation State of Two Wall Painting Panels from Pompeii Deposited in the Naples National Archaeological Museum (Italy)

Abstract: This work presents a methodology that combines spectroscopic speciation, performed through portable Raman spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and energy dispersive X-ray fluorescence spectrometry (ED-XRF) working in situ, and thermodynamic speciation to diagnose the environmental impacts, induced by past and current events, on two wall painting panels (Nos. 9103 and 9255) extracted more than 150 years ago from the walls of a Pompeian house (Marcus Lucretius House, Regio IX, Insula 3, House 5/24) and deposited in the Naples National Archaeological Museum (MANN). The results show a severe chemical attack of the acid gases that can be explained only by the action of H2S during and just after the eruption of the Vesuvius volcano, that expelled a high concentration of sulfur gases. This fact can be considered as the most important process impacting the wall painting panels deposited in the museum, while the rain-wash processes and the colonization of microorganisms have not been observed in contrast to the impacts shown by the wall paintings left outside in the archaeological site of Pompeii. Moreover, the systematic presence of lead traces and strontium in both wall paintings suggests their presence as impurities of the calcite mortars (intonacco) or calcite binder of these particular fresco Pompeian murals.

Standoff Detection of Geological Samples of Metal, Rock, and Soil at Low Pressures Using Laser-Induced Breakdown Spectroscopy:

Abstract: Categorized certified reference materials simulating metal, rock, soils, or dusts are used to demonstrate the standoff detection capability of laser-induced breakdown spectroscopy (LIBS) at severely low pressure conditions. A Q-switched Nd:YAG laser operating at 1064 nm with 17.2–50 mJ energy per pulse was used to obtain sample signals from a distance of 5.5 m; the detection sensitivity at pressures down to 0.01 torr was also analyzed. The signal intensity response to pressure changes is explained by the ionization energy and electronegativity of elements, and from the estimated full width half-maximum (FWHM) and electron density, the decrease in both background noise and line broadening makes it suitable for low pressure detection using the current standoff LIBS configuration. The univariate analyses further showed high correlation coefficients for geological samples. Therefore, the present work has extended the current state-of-the-art of standoff LIBS aimed at harsh environment detection.

Pharmaceutical Raw Material Identification Using Miniature Near-Infrared (MicroNIR) Spectroscopy and Supervised Pattern Recognition Using Support Vector Machine

Abstract: Near-infrared spectroscopy as a rapid and non-destructive analytical technique offers great advantages for pharmaceutical raw material identification (RMID) to fulfill the quality and safety requirements in pharmaceutical industry. In this study, we demonstrated the use of portable miniature near-infrared (MicroNIR) spectrometers for NIR-based pharmaceutical RMID and solved two challenges in this area, model transferability and large-scale classification, with the aid of support vector machine (SVM) modeling. We used a set of 19 pharmaceutical compounds including various active pharmaceutical ingredients (APIs) and excipients and six MicroNIR spectrometers to test model transferability. For the test of large-scale classification, we used another set of 253 pharmaceutical compounds comprised of both chemically and physically different APIs and excipients. We compared SVM with conventional chemometric modeling techniques, including soft independent modeling of class analogy, partial least squares discriminant analysis, linear discriminant analysis, and quadratic discriminant analysis. Support vector machine modeling using a linear kernel, especially when combined with a hierarchical scheme, exhibited excellent performance in both model transferability and large-scale classification. Hence, ultra-compact, portable and robust MicroNIR spectrometers coupled with SVM modeling can make on-site and in situ pharmaceutical RMID for large-volume applications highly achievable.

Differentiation of Body Fluid Stains on Fabrics Using External Reflection Fourier Transform Infrared Spectroscopy (FT-IR) and Chemometrics.

Abstract: Body fluids are evidence of great forensic interest due to the DNA extracted from them, which allows genetic identification of people. This study focuses on the discrimination among semen, vaginal fluid, and urine stains (main fluids in sexual crimes) placed on different colored cotton fabrics by external reflection Fourier transform infrared spectroscopy (FT-IR) combined with chemometrics. Semen–vaginal fluid mixtures and potential false positive substances commonly found in daily life such as soaps, milk, juices, and lotions were also studied. Results demonstrated that the IR spectral signature obtained for each body fluid allowed its identification and the correct classification of unknown stains by means of principal component analysis (PCA) and soft independent modeling of class analogy (SIMCA). Interestingly, results proved that these IR spectra did not show any bands due to the color of the fabric and no substance of those present in daily life which were analyzed, provided a false positive.

In-line Monitoring of Monomer and Polymer Content During Microgel Synthesis Using Precipitation Polymerization via Raman Spectroscopy and Indirect Hard Modeling.

Abstract: This contribution presents in-line monitoring of microgel synthesis by precipitation polymerization based on Raman spectroscopy. The spectra are evaluated via multivariate Indirect Hard Modeling (IHM) regression. Therefore, mechanistic models of the pure component spectra for solvent, monomer, and microgel are created by a sum of adaptable parameterized peak functions (Gaussian-Lorentzian). Instead of individual calibrations for each analyte, one comprehensive model is calibrated to predict both the monomer and microgel fraction while ensuring a consistent mass balance. As a novelty, this leads to an in-line microgel quantification based on an interactive spectral model. The results show cross-validation errors (RMSECV) of monomer and microgel fractions as low as 0.028 wt % and 0.084 wt %, respectively. The ability of IHM to account for non-linear spectral changes was found to reduce the microgel RMSECV by a factor of two compared to linear CLS regression. The calibration model allows simultaneous observation of the decrease in monomer content and the formation of microgels. Long as well as short focus immersion optics reveal characteristic vibrations of the turbid microgel suspension, although long focus optics are influenced by scattering particles to a greater extent. Precise examination of the model proves that the prediction is robust against changes in microgel particle size or temperature, which opens up the application of Raman spectroscopy as a comprehensive process analytical technology in microgel synthesis.

Realistic Instrumentation Platform for Active and Passive Optical Remote Sensing.

Abstract: We describe the development of a novel versatile optical platform for active and passive remote sensing of environmental parameters. Applications include assessment of vegetation status and water quality. The system is also adapted for ecological studies, such as identification of flying insects including agricultural pests. The system is based on two mid-size amateur astronomy telescopes, continuous-wave diode lasers at different wavelengths ranging from violet to the near infrared, and detector facilities including quadrant photodiodes, two-dimensional and line scan charge-coupled device cameras, and a compact digital spectrometer. Application examples include remote Ramanlaser-induced fluorescence monitoring of water quality at 120 m distance, and insect identification at kilometer ranges using the recorded wing beat frequency and its spectrum of overtones. Because of the low cost this developmental platform is very suitable for advanced research projects in developing countries and has, in fact, been multiplied during hands-on workshops and is now being used by a number of groups at African universities.

Screening of Astaxanthin-Hyperproducing Haematococcus pluvialis Using Fourier Transform Infrared (FT-IR) and Raman Microspectroscopy:

Abstract: Haematococcus pluvialis has promising applications owing to its ability to accumulate astaxanthin under stress conditions. In order to acquire higher astaxanthin productivity from H. pluvialis, it ...

The Colors of Keith Haring: A Spectroscopic Study on the Materials of the Mural Painting Tuttomondo and on Reference Contemporary Outdoor Paints.

Abstract: To date, little attention has been given to the scientific investigation of modern and contemporary mural paintings. This paper reports on: (1) the in situ spectroscopic analyses of the mural Tuttomondo (1989) painted by Keith Haring (1958-1990) in Pisa (Italy); and (2) the laboratory characterization of acrylic paints produced by Caparol Italy GmbH & Co., the original supplier of paint materials to the artist for the mural. Ultraviolet (UV), visible (Vis), and near-infrared (NIR) fiber optic reflectance spectroscopy (FORS) measurements were carried out in situ. The Caparol paint samples were characterized using benchtop instrumentation including both dispersive and Fourier transform Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR; with sample pre-treatment to remove filler interference in the fingerprint region), and UV-Vis-NIR FORS. This combined analytical approach confirmed that the materials used by Haring for the mural Tuttomondo have the same composition of the new Caparol acrylic paints, except for the case of the yellow pigment. This information offers valuable documentation for the materials history and for the conservation of a mural painting that is considered the last great public work by Haring.

Exploring a Hidden Painting Below the Surface of René Magritte's Le Portrait.

Abstract: Two state-of-the-art methods for non-invasive visualization of subsurface (or overpainted) pictorial layers present in painted works of art are employed to study Le portrait, painted by Belgian artist Rene Magritte in 1935. X-ray radiography, a commonly used method for the nondestructive inspection of paintings, had revealed the presence of an underlying figurative composition, part of an earlier Magritte painting entitled La pose enchantee (1927) which originally depicted two full length nude female figures with exaggerated facial features. On the one hand, macroscopic X-ray fluorescence analysis (MA-XRF), a method capable of providing information on the distribution of the key chemical elements present in many artists' pigments, was employed. The ability of the X-rays to penetrate the upper layer of paint enabled the imaging of the facial features of the female figure and provided information on Magritte's palette for both surface and hidden composition. On the other hand, visible and near infrared hyperspectral imaging spectroscopies in transmission mode were also used, especially in the area of the table cloth in order to look through the upper representation and reveal the pictorial layer(s) below. MA-XRF provided elemental information on the pigment distributions in both the final painting and the prior whereas the transmission mode provided information related to preparatory sketches as well as revealing differences between the paints used in both compositions. These results illustrate very well the manner in which the two imaging methods complement each other, both in the sense of providing different types of information on the nature and presence of paint components/pigments and in the sense of being optimally suited to easily penetrate through different types of overpaint.

Ultraviolet Stand-off Raman Measurements Using a Gated Spatial Heterodyne Raman Spectrometer:

Abstract: A spatial heterodyne Raman spectrometer (SHRS) is evaluated for stand-off Raman measurements in ambient light conditions using both ultraviolet (UV) and visible pulsed lasers with a gated ICCD detector. The wide acceptance angle of the SHRS simplifies optical coupling of the spectrometer to the telescope and does not require precise laser focusing or positioning of the laser on the sample. If the laser beam wanders or loses focus on the sample, as long as it is in the field of view of the SHRS, the Raman signal will still be collected. The SHRS is not overly susceptible to vibrations, and a vibration isolated optical table was not necessary for these measurements. The system performance was assessed by measuring stand-off UV and visible Raman spectra of a wide variety of materials at distances up to 18 m, using 266 nm and 532 nm pulsed lasers, with 12.4 in. and 3.8 in. aperture telescopes, respectively.

Combining Laser-Induced Breakdown Spectroscopy with Molecular Laser-Induced Fluorescence.

Abstract: We propose combining laser-induced breakdown spectroscopy (LIBS) with molecular laser-induced fluorescence (MLIF) with resulting plasma-borne molecules as a means of studying laser-induced plasma (LIP). Examples of this method with LIP-created Al, Si, and B monoxides are presented. Applicability of the LIBS-MLIF method for elemental and isotope analysis is demonstrated.

Portable Deep-Ultraviolet (DUV) Raman for Standoff Detection

Abstract: Alakai Defense Systems has recently developed a man-portable ultraviolet Raman spectrometer system. The portable Raman improvised explosives detector was designed to provide rapid, standoff detection of chemicals of interest to the end user, including, but not limited to explosives, narcotics, toxic industrial chemicals, and toxic industrial materials. In this paper, we discuss general aspects of the system design and user interface. Spectral and instrument performance data are shown for several common materials involved in narcotics manufacture, as well as cocaine and heroin, with comparisons to currently marketed handheld Raman instruments.

Online X-ray Fluorescence (XRF) Analysis of Heavy Metals in Pulverized Coal on a Conveyor Belt.

Abstract: Heavy metals in haze episode will continue to threaten the quality of public health around the world. In order to decrease the emission of heavy metals produced from coal burning, an online X-ray fluorescence (XRF) analyzer system, consisting of an XRF analyzer with data acquisition software and a laser rangefinder, was developed to carry out the measurement of heavy metals in pulverized coal. The XRF analyzer was mounted on a sled, which can effectively smooth the surface of pulverized coal and reduce the impact of surface roughness during online measurement. The laser rangefinder was mounted over the sled for measuring the distance between a pulverized coal sample and the analyzer. Several heavy metals and other elements in pulverized coal were online measured by the XRF analyzer directly above a conveyor belt. The limits of detection for Hg, Pb, Cr, Ti, Fe, and Ca by the analyzer were 44 ± 2, 34 ± 2, 17 ± 3, 41 ± 4, 19 ± 3, and 65 ± 2 mg·kg(-1), respectively. The relative standard deviation (%RSD) for the elements mentioned was less than 7.74%. By comparison with the results by inductively-coupled plasma mass spectrometry (ICP-MS), relative deviation (%D) of the online XRF analyzer was less than 10% for Cr, Ti, and Ca, in the range of 0.8-24.26% for Fe, and greater than 20% for Hg and Pb.

Fourier Transform Infrared Spectroscopy and Photoacoustic Spectroscopy for Saliva Analysis.

Abstract: Saliva provides a valuable tool for assessing oral and systemic diseases, but concentrations of salivary components are very small, calling the need for precise analysis methods. In this work, Fourier transform infrared (FT-IR) spectroscopy using transmission and photoacoustic (PA) modes were compared for quantitative analysis of saliva. The performance of these techniques was compared with a calibration series. The linearity of spectrum output was verified by using albumin-thiocyanate (SCN(-)) solution at different SCN(-) concentrations. Saliva samples used as a comparison were obtained from healthy subjects. Saliva droplets of 15 µL were applied on the silicon sample substrate, 6 drops for each specimen, and dried at 37 ℃ overnight. The measurements were carried out using an FT-IR spectrometer in conjunction with an accessory unit for PA measurements. The findings with both transmission and PA modes mirror each other. The major bands presented were 1500-1750 cm(-1) for proteins and 1050-1200 cm(-1) for carbohydrates. In addition, the distinct spectral band at 2050 cm(-1) derives from SCN(-) anions, which is converted by salivary peroxidases to hypothiocyanate (OSCN(-)). The correlation between the spectroscopic data with SCN(-) concentration (r > 0.990 for transmission and r = 0.967 for PA mode) was found to be significant (P < 0.01), thus promising to be utilized in future applications.

Quantitative Analysis of Carbon Steel with Multi-Line Internal Standard Calibration Method Using Laser-Induced Breakdown Spectroscopy

Abstract: A multi-line internal standard calibration method is proposed for the quantitative analysis of carbon steel using laser-induced breakdown spectroscopy (LIBS). A procedure based on the method was adopted to select the best calibration curves and the corresponding emission lines pairs automatically. Laser-induced breakdown spectroscopy experiments with carbon steel samples were performed, and C, Cr, and Mn were analyzed via the proposed method. Calibration curves of these elements were constructed via a traditional single line internal standard calibration method and a multi-line internal standard calibration method. The calibration curves obtained were evaluated with the determination coefficient, the root mean square error of cross-validation, and the average relative error of cross-validation. All of the parameters were improved significantly with the proposed method. The results show that accurate and stable calibration curves can be obtained efficiently via the multi-line internal standard calibration method.

Using Separable Nonnegative Matrix Factorization Techniques for the Analysis of Time-Resolved Raman Spectra:

Abstract: The key challenge of time-resolved Raman spectroscopy is the identification of the constituent species and the analysis of the kinetics of the underlying reaction network. In this work we present an integral approach that allows for determining both the component spectra and the rate constants simultaneously from a series of vibrational spectra. It is based on an algorithm for nonnegative matrix factorization that is applied to the experimental data set following a few pre-processing steps. As a prerequisite for physically unambiguous solutions, each component spectrum must include one vibrational band that does not significantly interfere with the vibrational bands of other species. The approach is applied to synthetic “experimental” spectra derived from model systems comprising a set of species with component spectra differing with respect to their degree of spectral interferences and signal-to-noise ratios. In each case, the species involved are connected via monomolecular reaction pathways. The potent...