bluuebunny/crossref_metadata_2025 huggingface dataset:
UV Resonance Raman Study of Domoic Acid, a Marine Neurotoxic Amino Acid
Authors: Yao Y. , Nelson W. H. , Hargraves P. , Zhang J.
Published: October 2003

Domoic acid, an amino acid neurotoxin, produces a single intense resonance Raman peak observed at 1652 cm−1 from aqueous solution when excited at either 242 or 257 nm. The detection limits for domoic acid in water are found to be well within those concentrations determined to be representative of values in toxic phytoplankton cells. Examination of cells known to contain identified large amounts of domoic acid shows that domoic acid spectra are sufficiently intensely excited to allow detection in the presence of normal phytoplankton cell constituents within the cell. Single cells from species established as producers of domoic acid, cultured under controlled conditions favorable to the production of domoic acid, produce spectra consistent with the presence of domoic acid in low concentrations.
Determination of the Relative Amount of Nucleic Acids and Proteins in Leukemic and Normal Lymphocytes by Means of Fourier Transform Infrared Microspectroscopy
Authors: Benedetti Edoardo , Bramanti Emilia , Papineschi Federico , Rossi Ilaria , Benedetti Enzo
Published: October 2003

Previous Fourier transform infrared (FT-IR) spectroscopic studies on neoplastic and normal cells have shown different band profiles and intensity associated with absorptions of proteins and nucleic acids. In the present study, an interpretation of such differences has been attempted by comparing the spectra of DNA/RNA/protein mixtures with the spectra, particularly, obtained for lymphocytes from B-chronic lymphatic leukemia (B-CLL) patients and normal donors. FT-IR microspectroscopy analysis showed a good agreement between the intensity and the band profile of the spectra of leukemic lymphocytes and those of the binary mixture made up of 75% human serum albumin and 25% DNA. The addition of small amounts of RNA (1–5%) modified the band shape, making it more similar to the spectrum of normal lymphocytes. An attempt was also made to estimate the relative amounts of DNA and RNA. The results demonstrated an increase in the DNA/RNA ratio value in neoplastic lymphocytes with respect to that reported in literature for normal ones.
Optical Emission Detection of Charged Particles after Selective Laser Ionization of Mercury Atoms in a Buffer Gas
Authors: Matveev O. I. , Mordoh L. S. , Clevenger W. L. , Smith B. W. , Winefordner J. D.
Published: October 2003

A method for the optical detection of the resonance ionization signal of mercury atoms in a buffer gas is described that is based on the emission from buffer gas atoms that are collisionally excited by interactions with electrons in a strong electric field. The first observations of this phenomenon are reported here, along with comparisons between optical and electrical detection. Advantages of a pulsed electric field over a continuous field are described. A wide range of possible applications for this type of gas phase detector are suggested.
Enhancing Effect of Deposited Silver on Surface-Enhanced Raman Scattering for Chemisorbed Benzyl Disulfide on Iron
Authors: Li Fengting , Lu Yun , Xue Gi
Published: October 2003

Benzyl disulfide (BDS) can be adsorbed on HCl- or H2SO4-etched iron plate to form self-assembled film. The films were characterized by Fourier transform surface-enhanced Raman scattering spectroscopy. It is proposed that the bands in the range of 290 to 296 cm−1in the spectra were due to the S–Fe bond. The disappearance of the S–S band, the large shifts of the C–S band, and the appearance of the Fe–S band from free BDS to the adsorbed molecule on the iron surface suggested that the BDS molecule was chemisorbed perpendicularly on the iron surface in the form of thiolate. The thiolates formed a film dotted with ferric hydroxide and silver cluster. The SERS effect of iron covered with BDS can be enhanced by the chemically deposited silver film, and the enhancing effect was related to the deposition time of silver.
Excitation Frequency Dependence and Fluorescence in the Raman Spectra of Al2O3
Authors: Aminzadeh A.
Published: October 2003

Raman spectra of aluminum oxide, Al2O3, have been a subject of interest over the last two decades. The origin of the fluorescence background in the Raman spectra of Al2O3 is still a subject of discussion. It has been believed to be due to hydrocarbon, iron ion impurities, or hydroxy groups on the surface of Al2O3. In this paper, Raman spectra of Al2O3 are reported that were acquired with different excitation frequencies as well as different spectrometers and different temperatures. It is shown that, whereas at an excitation frequency of 1064 nm a strong fluorescence background is observed, a sample of Al2O3 heated at 1250 °C when excited with a 632.8-nm frequency exhibits strong and remarkable fluorescence ne structure. It is concluded that the origin of the fluorescence background in the Raman spectra of Al2O3 is iron, and Fe impurity, and the intensity of this fluorescence depends upon the structure of Al2O3 and the excitation frequency used.
Multivariate Analysis of Mid-IR FT-IR Spectra of Hydrocarbon-Contaminated Wet Soils
Authors: Hazel G. , Bucholtz F. , Aggarwal I. D. , Nau G. , Ewing K. J.
Published: October 2003

This article describes a series of mid-IR FT-IR reflectance spectroscopy measurements of hydrocarbon-contaminated wet soils. The eventual goal of this work is the development of an analysis tool suitable for real-time in situ underground measurements where a suitable reference spectrum is not available. Multivariate analysis of the resulting spectral data indicates that the strongly varying wet soil matrix and the absence of a suitable reference spectrum in the field do not render this measurement technique unfeasible as a means of realizing remote in situ chemical detection in wet soils. It was also observed that simultaneous quantification of moisture content and identification of soil composition may be achieved. These results have important applications to in situ site characterization for environmental cleanup and soil characterization for construction planning.
Quantitative Detection of Gas-Phase NaOH Using 355-nm Multiple-Photon Absorption and Photofragment Fluorescence
Authors: Chadwick Bruce L. , Griffin Peter G. , Morrison Richard J. S.
Published: October 2003

The third-harmonic output of a Nd:YAG laser is utilized in the quantitative detection of gas-phase NaOH. Species selectivity and sensitivity are achieved via multiple-photon absorption and photo-dissociation of NaOH—in combination with monitoring of the subsequent Na photofragment fluorescence. Detection limits of ∼0.5 ppm of gas-phase NaOH have been achieved under atmospheric conditions. The fluorescence intensity has been found to be proportional to the square of the laser power, which is consistent with a second-order absorption process. Although the technique is less sensitive than the more widely used excimer laser-induced photofragment fluorescence approach, there are many technical advantages which make it more suitable for use in modern coal combustion systems. These combustion systems require accurate alkali measurement and control to combat fouling and corrosion of process surfaces and turbine blades.
Quantitative Comparison of Five SERS Substrates: Sensitivity and Limit of Detection
Authors: Norrod Karen L. , Sudnik Leo M. , Rousell David , Rowlen Kathy L.
Published: October 2003

Five surface-enhanced Raman scattering (SERS) substrates were quantitatively compared for ease of preparation, sensitivity, limit of detection (LOD), reproducibility, and stability. Specifically, vapor-deposited Ag films, electrochemically roughened Ag electrodes, nitric acid-etched Ag foil, Tollens-produced Ag films, and photore-duced Ag films on TiO2 were examined. Of these substrates, post-deposition-annealed Ag films exhibited the greatest sensitivity and lowest LOD, with 152 ± 1 counts per femtomole and an LOD of 0.36 ± 0.02 femtomoles of trans-1,2-bis(4-pyridyl)ethene (BPE). The substrate demonstrating the poorest sensitivity and highest LOD was Ag deposited from the Tollens reaction, with 0.38 ± 0.01 counts per femtomole and an LOD of 270 ± 20 femtomoles of BPE. The easiest substrate to prepare, nitric acid-etched Ag foils, exhibited a sensitivity of 0.485 ± 0.008 counts per femtomole and an LOD of 200 ± 10 femtomoles of BPE.
DNA—Dye Fluorescence Enhancement Based on Shifting the Dimer—Monomer Equilibrium of Fluorescent Dye
Authors: Guo Xiang-Qun , Zhang Zu-Lin , Zhao Yi-Bing , Wang Dong-Yuan , Xu Jin-Gou
Published: October 2003

In this paper, the investigation of DNA–dye fluorescence enhancement based on shifting the dimer–monomer equilibrium of a fluorescent dye, acridine orange (AO), is reported. Formation of a virtually nonfluorescent dimeric dye, acridine orange homodimer (AOAO), induced by the pre-micellar aggregation of an anionic surfactant, sodium dodecyl sulfate (SDS), was observed. The possibility of using the in situ formed AOAO as a fluorescent probe for nucleic acids and polynucleotides was studied. The results showed that a nearly 1000-fold fluorescence enhancement was observed upon addition of calf thymus DNA (CT DNA). The fluorescence enhancement effect of DNA was thought to be based on the DNA modulated shift of the dimmer monomer equilibrium of AO in the anionic surfactant solution. Intercalation of the monomer in DNA caused the dissociation of AOAO and led to a very high fluorescence enhancement. It seemed that the dimeric dye molecules acted as a source of monomer molecules ready for interacting with nucleic acids and, at the same time, decreased the inherent fluorescence of monomer molecules, which proved to be unfavorable to the detection of fluorescence enhancement. A linear dependence of fluorescence intensity on CT DNA concentration over a range from 7.8 ng/mL to 10.0 g/mL, in the presence of AO at a concentration of 1.65 × 10−6mol/L and of SDS at a concentration of 8.0 × 10−4 mol/L, allowed sensitive quantitation of CT DNA in a conventional fluorometer. Calibration graphs for yeast RNA and polynucleotides, such as poly A, poly U, and poly I, were also obtained.
Forward Degenerate Four-Wave Mixing as a Detection Method in Liquid Separation Systems: Improving Detection Limits by Means of a Fabry—Perot Interferometer
Authors: Hoornweg Gerard Ph. , De Beer Tjipke , Velthorst Nel H. , Gooijer Cees
Published: October 2003

A simple, small, and low-resolution confocal Fabry–Perot interferometer (CFP) has been developed to improve the signal-to-noise ratio (S/N) in forward degenerate four-wave mixing (F-D4WM) detection, coupled to high-performance liquid chromatography (HPLC). Its appropriateness is based on the difference in coherence between the F-D4WM signal and the background stray light. A detailed description of the specially designed CFP and its performance is presented. The improvement in S/N was calculated from the chromatographic peaks recorded after an HPLC separation of 1- and 2-aminoanthraquinone. The concentration limit of detection (LOD) was improved by a factor of 30; for 1-aminoanthraquinone it was 2 × 10−8 M injected (corresponding to about 3 × 10−9 M in the detector cell), which is quite favorable in view of its low molar extinction coefficient being 2000 M−1 cm−1 at the utilized laser wavelength (514.5 nm).
Spatial and Temporal Dependence of Lead Emission in Laser-Induced Breakdown Spectroscopy
Authors: Castle B. C. , Visser K. , Smith B. W. , Winefordner J. D.
Published: October 2003

Two-dimensional images of the distribution in space and time of the chemical species associated with the spectral emission from a laser-induced breakdown (LIB) plasma on a solid sample were captured. The time-dependent spatial shape and size of the plasma, viewed simultaneously from two orthogonal directions, were measured in terms of the emission from a lead ionic line and a set of lead atomic lines. The temporal and spatial behavior are characteristically different for the different spectral lines. The ionic emission (220 nm) is confined to a smaller, more concentrated central part of the LIB plasma, whereas the atomic emission (280 nm) is more evenly dispersed over the entire plasma. A protrusion of the plasma was observed where there was no significant emission at 220 or 280 nm. Time-resolved spectral imaging has the potential to considerably improve analytical LIB spectroscopy (LIBS) results and lead to a better fundamental understanding of its behavior.
Laser Diagnostics of Painted Artworks: Laser-Induced Breakdown Spectroscopy in Pigment Identification
Authors: Anglos Demetrios , Couris Stelios , Fotakis Costas
Published: October 2003

Laser-induced breakdown spectroscopy (LIBS) was employed for the in situ analysis of pigments used in painting. LIBS spectra were collected from a wide variety of pigments in powder form and in oil color test samples. Appropriate emission lines for the identification of the metallic elements in the pigments examined are proposed. Under optimal experimental parameters, the technique is minimally destructive; two pulses from a laser beam focused on the sample surface result in the formation of a small crater with typical diameter around 40 μm and depth of no more than 10 μm. Furthermore, recording LIBS spectra from successive laser pulses on the same spot of a model oil painting resulted in information regarding the pigment composition of several paint layers, showing the capability of the technique in performing depth profile analysis. Finally, a test case is presented in which an 18th century oil painting, subjected to partial restoration, was examined by LIBS, and the different pigments used in the original and in the restored part of the work were clearly identified. The results of our studies demonstrate the applicability of LIBS in the rapid, in situ, and practically nondestructive determination of pigments in painted artworks.
Phase-Resolved Fluorescence Spectral and Lifetime Characterization of Commercial Humic Substances
Authors: Hemmingsen Sherry L. , McGown Linda B.
Published: October 2003

Phase-resolved excitation-emission matrices (PREEMs) are shown to provide a unique visual representation of the intrinsic fluorescence properties of humic acids under a variety of solution conditions. The calculation of spectral peak ratios in PREEMs as well as steady-state excitation-emission matrices provides a convenient means for quantitating differences between the spectra with good precision. Absorbance correction is shown to be essential for accurate comparison among spectral features. Increased detail is available from PREEMs at various modulation frequencies that reveal the distribution of fluorescence lifetime contributions across the spectral surface. Direct measurement of fluorescence lifetime recovered three ranges of lifetime components in the humic substances, <1 ns, 2–5 ns, and 8–14 ns, that are consistent with previously reported lifetimes. PREEMs, which provide a concise “survey” of how the lifetimes change across the spectrum, may aid in pinpointing spectral regions that provide the best lifetime discrimination among samples.
Depth Profiling of Thick Layers of Graded Metal—Zirconia Ceramic Coatings Using Laser Ablation Inductively Coupled Plasma Atomic Emission Spectrometry
Authors: Kanicky Viktor , Novotny Ivan , Musil Jan , Mermet Jean-Michel
Published: October 2003

The feasibility of depth profiling of thick layers (>100 μm) consisting of partially stabilized zirconia coating and graded metal—ceramic coating on Inconel steel (ZrO2–Y2O3/NiCrAlY/steel and ZrO2–CeO2/NiCrAlY/steel) was studied on the basis of the use of laser ablation inductively coupled plasma atomic emission spectrometry (LA-ICP-AES). An ICP spectrometer equipped with a multichannel detection was used for the simultaneous measurements of the line intensities. The ablation was performed with a Nd:YAG laser operated in a Q-switched mode at 266 nm. To study the erosion rate, we used either a static or a translation mode for the ablation, and the corresponding temporal behavior of the signals was studied. A higher erosion rate was found for the translation mode when depths higher than several hundred micrometers were probed.
Comparison between Direct-Current and Radio-Frequency Gas-Jet-Boosted Glow Discharge Atomic Emission Spectrometry for the Analysis of Steel
Authors: Cho Won B. , Woo Young A. , Kim Hyo J. , Kim Il J. , Kang Won K.
Published: October 2003

Comparisons between direct-current (dc) and radio-frequency (rf) gas jet-boosted glow discharge atomic emission spectrometry (GD-AES) have been made with regard to fundamental characteristics and analytical performance. The study of fundamental characteristics includes the voltage—current relationship; a gas flow rate of 0 mL/min to 800 mL/min and pressures ranging from 3 Torr to 5 Torr on dc bias potential; the sample weight loss; and the emission intensity. The dc-powered glow discharge at 90 mA/450 V and 60 mA/710 V at 5 Torr shows 3 × more sample weight loss than the rf discharge at 40 W. Radio-frequency glow discharge shows a short-term precision of <1% relative standard deviation (RSD) and a long-term stability of <5% RSD for both major and trace element lines. Both rf and dc show calibration curves that are linear over 2–3 orders of magnitude, with a general improvement in linearity from ratioing the signal to an internal standard of the matrix. Further improvement of linearity was possible by correcting the bias potential in the rf glow discharge. Limits of detection (LODs) for rf are tens of parts per billion from many trace elements in low-alloy steel, which is one order of magnitude improvement over those for dc.
Deviation from the Lambert Law in Ultrathin Films Such as Black Soap Films
Authors: Tano Takanori , Umemura Junzo
Published: October 2003

A theoretical investigation has been made of the difference in absorbance between that calculated from the Lambert law and that from thin-layer optics which fully takes into account the effect of multiple reflections on a symmetrical five-layer film such as black soap film. The absorbance of a black soap film can be very different from that of a thick film because of interference effects. The error involved may be as large as 25%. In addition, for both three-layer and symmetrical five-layer films, general approximate equations are presented for the absorbance by a stratified medium due to the presence of an absorbing layer. These equations are appropriate for film thickness on the order of 50 nm for incident radiation at 3400 cm−1 and are accurate to less than 2.5% error.
Influence of Atmosphere and Irradiation Wavelength on Copper Plasma Emission Induced by Excimer and Q-Switched Nd:YAG Laser Ablation
Authors: Lee Yong-Ill , Song Kyuseok , Cha Hyong-Ki , Lee Jong-Min , Park Min-Chun , Lee Gae-Ho , Sneddon Joseph
Published: October 2003

Laser-induced copper plasma emission was investigated by time-integrated spatially resolved spectrometry. The comparative work on the plasma emission characteristics—specifically, self-absorption, line broadening, emission intensity, and metal ion formation—was carried out by the use of two different laser systems (XeCl excimer: = 308 nm; Nd:YAG: = 1064 and 532 nm). The characteristics of plasma emission produced by different wavelength radiation on copper atomic and ion lines under various atmospheric gases (argon, neon, and helium) and pressures (760–10 Torr) are presented. The differences in self-absorption and line broadening phenomena in the plasma location were explained by shock wave-driven excitation mechanism for atoms in the outer region in the plasma. The excitation temperatures of the plasma induced by 308- or 532-nm irradiation were also much higher that those induced by 1064-nm irradiation.
Evaluation of Two Commercially Available TLC Materials as SER Substrates
Authors: Szabo Nancy J. , Winefordner James D.
Published: October 2003

Two commercially available thin-layer chromatographic plates were evaluated as substrates for routine analysis by surface-enhanced Raman spectrometry (SERS). One plate was purchased precoated with silver; the other was coated in-house via chemical reduction. The use of SERS as a detection method for thin-layer chromatography (TLC) was also considered. To this end, a mixture of commonly used sulfonamides was separated and detected directly from each plate. The mobilities of the sulfa drugs were not strongly affected by the silver, but Raman response was weak and analyte degradation was apparent. Improvement was found through modification of the surface by adding a thin film of water to the substrate. Overall substrate performance was evaluated with the use of crystal violet as the model analyte in both dry and dampened states. Signal vs. concentration curves were linear across at least two orders of magnitude with limits of detection in the low- to sub-ng range (total analyte applied). Under routine preparation and analysis procedures, reproducibility was generally <30%, but improved to ∼10% when greater care was applied. Typical spectra for two compound series having a variety of functional groups were obtained, showing the substrates to be moderately active.
Improvements in the Use of Attenuated Total Reflection Fourier Transform Infrared Dichroism for Measuring Surface Orientation in Polymers
Authors: Everall Neil J. , Bibby Arran
Published: October 2003

Improvements in the use of attenuated total reflection (ATR) Fourier transform infrared (FT-IR) dichroism for measuring surface orientation in polymer films are described, with poly(ethylene terephthalate) (PET) as an example material. It is shown that normalizing band intensities relative to a nondichroic band, prior to calculating dichroic ratios, eliminates the need to maintain identical contact areas/pressures when removing, rotating, and reclamping samples to the ATR element, which has been a major historical drawback to this technique. The normalization is vital; it makes the calculated dichroic ratios largely insensitive to variations in sample/prism contact area, and less sensitive to uncertainties in the refractive indices and birefringence of the polymer. For PET, it is shown that the birefringence can be neglected in the analysis, and a single approximate refractive index used. This is a significant benefit since the birefringence will vary as a function of orientation and crystallinity. Polymers that are much more birefringent than PET can also be analyzed by using the formalism described in this paper, provided that the three independent indices are known. This paper is presented in two parts; first, equations are derived which allow the calculation of all second-order orientation parameters ( P200, P220, P202, and P222), and the averaged squared direction cosines, from the normalized ATR dichroic ratios. Second, we show how a single-reflection diamond ATR unit is an ideal tool for this work, since it allows small, hard, or irregularly shaped samples to be examined without fear of damaging the ATR element. We illustrate the technique using data obtained from a series of uniaxially drawn films, and one biaxially drawn film, using a commercially available accessory. From these data, orientation parameters were calculated as a function of draw ratio and compared with those obtained from specular-reflectance FT-IR and birefringence analysis of the same samples. The method should be applicable to any polymer provided that (1) a suitable nondichroic band is available for normalization and (2) the largest polymer refractive index lies well below that of the ATR element (2.4 in the case of diamond). It must be realized that condition 1 is not trivial; careful investigation is required to identify truly nondichroic bands (if any exist for the polymer of interest).
Imaging Neurotransmitter Uptake and Depletion in Astrocytes
Authors: Tan Weihong , Haydon Philip G. , Yeung Edward S.
Published: October 2003

An ultraviolet (UV) laser-based optical microscope and charge-coupled device (CCD) detection system was used to obtain chemical images of biological cells. Subcellularstructures can be easily seen in both optical and fluorescence images. Laser-induced native fluorescence detection provides high sensitivity and low limits of detection, and it does not require coupling to fluorescent dyes. We were able to quantitatively monitor serotonin that has been taken up into and released from individual astrocytes on the basis of its native fluorescence. Different regions of the cells took up different amounts of serotonin with a variety of uptake kinetics. Similarly, we observed different serotonin depletion dynamics in different astrocyte regions. There were also some astrocyte areas where no serotonin uptake or depletion was observed. Potential applications include the mapping of other biogenic species in cells as well as the ability to image their release from specific regions of cells in response to external stimuli.
Use of Pyrolysis Mass Spectrometry with Supervised Learning for the Assessment of the Adulteration of Milk of Different Species
Authors: Goodacre Royston
Published: October 2003

Binary mixtures of 0–20% cows' milk with ewes' milk, 0–20% cows' milk with goats' milk, and 0–5% cows' milk with goats' milk were subjected to pyrolysis mass spectrometry (PyMS). For analysis of the pyrolysis mass spectra so as to determine the percentage adulteration of either caprine or ovine milk with bovine milk, partial least-squares regression (PLS), principal components regression (PCR) and fully interconnected feed-forward artificial neural networks (ANNs) were studied. In the latter case, the weights were modified by using the standard back-propagation algorithm, and the nodes used a sigmoidal squashing function. It was found that each of the methods could be used to provide calibration models which gave excellent predictions for the percentage adulteration with cows' milk to <1% for samples, with an accuracy of ±0.5%, on which they had not been trained. Scaling the individual nodes on the input layer of ANNs significantly decreased the time taken for the ANNs to learn, compared with scaling across the whole mass range; however in one case this approach resulted in poor generalization for the estimates of percentage cows' milk in ewes' milk. To assess whether the calibration models had learned the differences between the milk species or the differences due to the different fat content of in each of the milk types, we also analyzed pure milk samples varying in fat content by PyMS. Cluster analysis showed unequivocally that the major variation between the different milk species was not due to variable fat content. Since any biological material can be pyrolyzed in this way, the combination of PyMS with supervised learning constitutes a rapid, powerful, and novel approach to the quantitative assessment of food adulteration generally.
Nondestructive Discrimination of Biological Materials by Near-Infrared Fourier Transform Raman Spectroscopy and Chemometrics: Discrimination among Hard and Soft Ivories of African Elephants and Mammoth Tusks and Prediction of Specific Gravity of the Ivories
Authors: Shimoyama Masahiko , Maeda Hisashi , Sato Hidetoshi , Ninomiya Toshio , Ozaki Yukihiro
Published: October 2003

This paper demonstrates the usefulness of near-infrared (NIR) Fourier transform (FT) Raman spectroscopy and chemometrics in nondestructive discrimination of biological materials. The discrimination among three kinds of materials—hard ivories, soft ivories, and mammoth tusks—has been investigated as an example. NIR (1064-nm) excited FT-Raman spectra were measured in situ for these materials, and principal component analysis (PCA) of the obtained spectra was carried out over the 1800–400-cm−1 region. The two kinds of ivories are clearly discriminated from one another on the basis of a one-factor plot. It was found that treatment of the Raman data by multiplicative scatter correction (MSC) greatly improves the ability to discriminate. Principal component weight loadings show that the discrimination relies upon the ratio of collagen and hydroxyapatite included in two kinds of ivories. The discrimination among the hard and soft ivories and mammoth tusks was made by a three-factor plot for FT-Raman spectra after the MSC treatments. Partial least-squares regression (PLSR) enabled us to make a calibration model which predicts the specific gravity of the hard and soft ivories.
Three New Organic Scintillators with Large Stokes Shifts
Authors: Barni E. , Viscardi G. , D'Ambrosio C. , Leutz H. , Puertolas D. , Tailhardat S. , Destruel P. , Jolinat P. , Güsten H.
Published: October 2003

Three new organic scintillators (PMP-410, PMP470, and PMP480) were synthesized on the basis of 1-phenyl-3-mesityl-2-pyrazoline (PMP). Their synthesis and their polymerization in polystyrene are described. We measured their Stokes shifts in polystyrene (∼1.3 eV) between their absorption maxima (PMP-410: 287 nm; PMP-470: 315 nm; PMP-480: 314 nm) and their emission maxima (PMP-410: 408 nm; PMP-470: 480 nm; PMP-480: 479 nm). Absorption and emission maxima, Stokes shifts, and light yields of all eight pyrazoline scintillators so far synthesized are listed and are compared with results for 3-hydroxyflavone (3-HF). The advantages of these one-component dopants are discussed with respect to the usually applied two-component (scintillator plus wavelength shifter) dopants.
Determination of Protein in Ground Wheat Samples by Mid-Infrared Diffuse Reflectance Spectroscopy
Authors: Reeves James B. , Delwiche Stephen R.
Published: October 2003

The objective of this study was to determine whether mid-infrared diffuse reflectance spectroscopy could be used in the same manner as near-infrared diffuse reflectance spectroscopy to quantitatively determine the protein content of ground wheat samples. One hundred and thirty hard red winter wheat samples were assayed for protein by combustion and scanned in the near- and mid-infrared. Samples (UDY ground) were scanned neat in the near-infrared from 1100 nm (9091 cm−1) to 2498 nm (4003 cm−1) on a scanning monochromator and in the mid-infrared from 4000 cm−1 (2500 nm) to 400 cm−1 (25,000 nm) on a Fourier transform spectrometer at 4-and 16-cm−1 resolutions. Protein content varied from a low of 8.98% to a high of 18.70% (average of 12.86% with a standard deviation of 1.66%). Calibrations developed with the use of partial least-squares gave an R2 and bias-corrected standard error of performance of 0.999 and 0.054 for the near-infrared and 0.997 and 0.085 for the mid-infrared (4 cm−1 resolution). Calibration results based on mid-infrared spectra, while not as good as those for near-infrared spectra, were nevertheless quite good. These results demonstrate that it is possible to develop satisfactory calibrations for protein in ground wheat with the use of mid-infrared spectra without the need for sample dilution with KBr.
Urinary Stone Layer Analysis of Mineral Components by Raman Spectroscopy, IR Spectroscopy, and X-ray Powder Diffraction: A Comparative Study
Authors: Kontoyannis C. G. , Bouropoulos N. C. , Koutsoukos P. G.
Published: October 2003

Mineral components of a urinary stone forming layers have been analyzed with the use of Raman spectroscopy (RS), Fourier transform infrared spectroscopy (FT-IR), and X-ray powder diffraction (XRD). The three spectroscopic methods were compared with respect to their capability of yielding reliable analytical qualitative results. The application of RS yielded less crowded spectra with sharper bands in comparison with those obtained by FT-IR. The analysis of the various mineral layers found in a human stone was possible with RS by focusing the laser beam at the desired layer. Overlapping broad bands were produced from the application of FT-IR, which made it difficult to identify components whose bands showed overlapping. Powder XRD could not be used for accurate analysis of the mineral components of the various stone layers since the material contained in the layers of small stones is not sufficient for analytical purposes. Moreover, the necessary stone grinding precludes the possibility of mineral topological analysis.
Optimal Wavelength Range Selection by a Genetic Algorithm for Discrimination Purposes in Spectroscopic Infrared Imaging
Authors: Van Den Broek W. H. A. M. , Wienke D. , Melssen W. J. , Buydens L. M. C.
Published: October 2003

When spectroscopic infrared imaging is applied to discriminate between different materials, multiple images have to be measured at different wavelengths or wavelength ranges. The time-consuming step in present on-line spectroscopic imaging is the measurement and processing time per identification of a number of spectroscopic images. If this number of images can be kept small, whereby an optimal discrimination is still guaranteed, the acquisition and processing time will be faster and, therefore, this approach becomes attractive in real-world applications. This paper describes the search for a limited number of spectroscopic wavelengths or wavelength ranges for images where optimal discrimination between the materials is guaranteed. This optimization is applied in particular to the discrimination between plastics and nonplastics. Because the number of potential wavelength combinations is huge, a genetic algorithm (GA) is used as a subset selection technique to solve this large-scale optimization problem. Since the problem concerns classification, a specific optimization criterion is developed. Finally, infrared images are measured at the calculated optimal wavelength ranges, and the resulting discrimination performance is compared with that of images measured at wavelengths chosen on the basis of a priori spectroscopic knowledge.
Two-Dimensional Imaging of Flame Species Using Two-Photon Laser-Induced Fluorescence
Authors: Georgiev Nikola , Aldén Marcus
Published: October 2003

The potential for two-dimensional visualization of combustion species by using two-photon laser-induced fluorescence (LIF) has been investigated. The technique was applied for two-dimensional (2D) imaging of carbon monoxide, ammonia, oxygen, and hydrogen atoms in flames. Approaches for compensating the signal intensity for the quadratic laser intensity dependence in two-photon imaging are discussed. For the case of CO and H atom visualization, a potential problem is the interference from nonresonantly excited C2, whose emission spectrally and spatially coincides with the fluorescence from CO. Different strategies for elimination of the C2 emission were investigated. It was found out that the emissions from CO and C2 can be separated in time. For the case of the oxygen atoms, it was observed that the relation between the intensities of the fluorescence signals at 845 and 777 nm changes with the equivalence ratio of the investigated flame. An attempt to estimate the 2D detection limit for these species in flames is also made.
Phase-Resolved Depth Profiling of Thin-Layered Plasma Polymer Films by Step-Scan Fourier Transform Infrared Photoacoustic Spectroscopy
Authors: Jiang Eric Y. , Palmer Richard A. , Barr Nancy E. , Morosoff Nicholas
Published: October 2003

After reviewing the background of step-scan interferometric photoacoustic spectroscopy, this paper describes a step-scan Fourier transform photoacoustic phase-resolved technique and its applications in depth profiling of micrometer -thick layered plasma polymers. In particular, the power of direct use of the photoacoustic phase spectrum in both qualitative and quantitative depth profiling of the layered samples is extensively discussed. The effects of both spatial origin and intensity of a photoacoustic signal on its phase have been explicitly analyzed for both overlapping and distinctive, nonoverlapping, bands of the thin-layered plasma polymer samples. The phase spectrum technique is shown to be a very effective and efficient method of spectral depth profiling analysis.
Study of Impulse Polymer Rheo-Optics by Step-Scan FT-IR Time-Resolved Spectroscopy
Authors: Wang Haochuan , Palmer Richard A. , Manning Christopher J.
Published: October 2003

The applicability of step-scan impulse/response FT-IR spectroscopy to the rheo-optical study of polymer films is demonstrated by spectral measurements with isotactic polypropylene. A novel piezoelectrically driven microrheometer is employed to apply repetitive impulses to a polymer sample while time-domain spectra are recorded by step-scan FT-IR spectroscopy. The traditional advantages of Fourier transform spectroscopy are retained while providing a second multiplex advantage for the characterization of the time-dependence of the sample response. Reproducible results, consistent with the frequency-domain literature data and having good signal-to-noise ratio, are obtained. The spectral changes due to molecular reorientation are found to be essentially as fast as the mechanical stretching, also consistent with frequency-domain results. To our knowledge, this is the first reported step-scan FT-IR time-domain rheo-optical measurement. This technique appears to be applicable to a variety of polymer samples. The advantages of time-domain measurements over frequency-domain measurements are briefly discussed.
Trace Element Analysis in Water by the Laser-Induced Breakdown Spectroscopy Technique
Authors: Arca G. , Ciucci A. , Palleschi V. , Rastelli S. , Tognoni E.
Published: October 2003

In this paper, results are presented showing the feasibility of the laser-induced breakdown spectroscopy (LIBS) technique as a fast and sensitive analytic tool for quantitative measurement of trace elements in water. Many ionic elements were detected; the system linearity was tested by analyzing water samples containing known concentration of Mg and Ca, whereas Cr-polluted samples were exploited to test the system sensitivity limit to impurities.
Event-Locked Time-Resolved Fourier Spectroscopy
Authors: Weidner H. , Peale R. E.
Published: October 2003

A low-cost method of adding time-resolving capability to commercial Fourier transform spectrometers with a continuously scanning Michelson interferometer has been developed. This method is specifically designed to eliminate noise and artifacts caused by mirror-speed variations in the interferometer. The method exists of two parts: (1) a novel timing scheme for synchronizing the transient events under study and the digitizing of the interferogram and (2) a mathematical algorithm for extracting the spectral information from the recorded data. The novel timing scheme is a modification of the well-known interleaved, or stroboscopic, method. It achieves the same timing accuracy, signal-to-noise ratio, and freedom from artifacts as step-scan time-resolving Fourier spectrometers by locking the sampling of the interferogram to a stable time base rather than to the occurrences of the HeNe fringes. The necessary pathlength-difference information at which samples are taken is obtained from a record of the mirror speed. The resulting interferograms with uneven pathlength-difference spacings are transformed into wavenumber space by least-squares fits of periodic functions. Spectra from the far-infrared to the upper visible at resolutions up to 0.2 cm−1 are used to demonstrate the utility of this method.
Study of Diagnosis Criteria for Pathological Tissues by Laser-Induced Fluorescence
Authors: Meirong Lin , Zhengrong Lu , Fang Fang , Jia Li , Baozheng Zhang
Published: October 2003

It has been confirmed that the differences in fluorescence spectra of normal and pathological biotissues can be used as a sensitive and nondestructive diagnostic probe. However, experiments show that not only are the fluorescence spectral features of different tissues very different but the features of the same tissue under different detection conditions are different too. Therefore, the diagnosis criteria of pathological tissues must be changed in accordance with different spectral features. In this paper, several diagnosis methods using native fluorescence characteristics of biotissues given in existing reports are analyzed. With the fourth harmonic at 266 nm of a Q-switched YAG laser as an excitation source, laser-induced fluorescence (LIF) spectra of native human normal and pathological breast and blood vessel tissues in vitro were measured and studied. According to their spectral characteristics, two diagnosis criteria are suggested: by the fluorescence intensity ratios at several specific wavelengths, cancerous (with p < 0.001) and benign tumor ( p < 0.005) can be distinguished from the normal tissue; by the fluorescence intensity ratios of the two main peaks, atherosclerotic plague and thrombus (both with p < 0.005) can be distinguished from normal blood vessel. In order to make comparisons with the results from human cancerous breast tissues, spectra of a model mouse were also observed.
Classification of Vegetable Oils by FT-IR
Authors: Dahlberg Donald B. , Lee Shawn M. , Wenger Seth J. , Vargo Julie A.
Published: October 2003

The Fourier transform infrared (FT-IR) spectra of 27 brands of 10 types of cooking oils and margarines were measured without temperature control. Attempts to predict the vegetable source and physical properties of these oils failed until wavelength selection and multiplicative signal correction (MSC) were applied to the FT-IR spectra. After pretreatment of the data, principal component analysis (PCA) was totally successful at oil identification, and partial least-squares (PLS) models were able to predict both the refractive indices [standard error of estimation (SEE) 0.0002] and the viscosities (SEE 0.52 cP) of the oils. These models were based predominately on the FT-IR detection of the cis and trans double-bond content of the oils, as well as small amounts of defining impurities in sesame oils. Efforts to use selected wavelengths to discriminate oil sources were only partially successful. These results show the potential utility of FT-IR in the fast detection of substitution or adulteration of products like cooking oils.
On-Line Monitoring of Laser Cleaning of Limestone by Laser-Induced Breakdown Spectroscopy and Laser-Induced Fluorescence
Authors: Gobernado-Mitre I. , Prieto A. C. , Zafiropulos V. , Spetsidou Y. , Fotakis C.
Published: October 2003

The application of laser-induced breakdown spectroscopy (LIBS) to monitor the laser cleaning process of polluted limestone from a historic building is examined. The combination of a Q-switched Nd: YAG pulsed laser with on-line diagnostics by the LIBS technique is shown to be very useful for controlling and characterizing the cleaning process in order to avoid overcleaning. In addition, the coupling of this spectroscopic technique to the cleaning process provides important information about the optimal experimental conditions to be selected for achieving an adequate cleaning procedure. Furthermore, the spectroscopic study of the plasma emission can be used to determine the elemental composition of both the black crust and the underlying stone. The application of LIBS as a diagnostic technique to monitor and control the laser cleaning process of limestone is based on the different elemental composition of the black encrustations covering the stone surface and the underlying stone. On the other hand, a different experimental setup for probing the ablation products by laser-induced fluorescence (LIF), in order to achieve a signal amplification of some atomic emission lines with weak intensity in the LIBS spectrum, is described.
Investigation of the Degradation Products of Archaeological Linens by Raman Spectroscopy
Authors: Edwards H. G. M. , Falk M. J.
Published: October 2003

The yellow-brown coloration formed in the degradation process of linen fabrics has been studied by Raman spectroscopy. Aqueous extracts from documented linens from the Egyptian XIIth Dynasty (ca. 4000 y BP) and Kasr-el-Yahud (ca. 1350 y BP) have been used to investigate the chemical basis of the degradation process; the pale-yellow crystalline material isolated from these extracts shows evidence of OH, C =C, C–C, and hydrocarbon groups. Several possibilities for the ring scission of cellulose under archaeological conditions are addressed.
6-Propionyl-2-(N,N-dimethylamino)naphthalene (PRODAN) Revisited
Authors: Sun Shiying , Heitz Mark P. , Perez Sheryl A. , Colón Luis A. , Bruckenstein Stanley , Bright Frank V.
Published: October 2003

The photophysics of 6-propionyl-2-( N,N-dimethylamino)naphthalene (PRODAN) in liquid water are reported. Our results demonstrate that the often mentioned extra blue-edge shoulder seen for PRODAN in liquid water is a result of PRODAN—PRODAN intermolecular interactions in a supersaturated PRODAN solution and not a consequence of impurities in the commercial PRODAN preparations. In all cases where the aqueous PRODAN solution is not supersaturated, there is no detectable blue-edge emission shoulder.
Diffuse Reflectance and Transmittance Spectroscopy for the Quantitative Determination of Scattering and Absorption Coefficients in Quantitative Powder Analysis
Authors: Burger T. , Ploss H. J. , Kuhn J. , Ebel S. , Fricke J.
Published: October 2003

A three-flux approximation of the equation of radiative transfer is used to separately determine the effective specific scattering and absorption coefficients of powder mixtures from hemispherical reflectance and transmittance measurements. For a two-component mixture of lactose and paracetamol, it is demonstrated how the knowledge of the separately known scattering coefficient can be used to improve partial least-squares regression (PLS) calibrations of diffuse reflectance data pretreated by multiplicative scatter correction (MSC). Furthermore it is shown that the measured specific absorption coefficient of the investigated mixtures is not generally a linear function of the constituents concentration, a result which might be caused by the mixing procedure of the samples. With the use of the absorption coefficient, it is demonstrated that artificial neural networks are superior to PLS calibrations when modeling a nonlinear relation.
Multivariate Calibration Models Based on the Direct Analysis of Near-Infrared Single-Beam Spectra
Authors: Lu Geng , Zhou Xiangji , Arnold Mark A. , Small Gary W.
Published: October 2003

Multivariate calibration models are generated for glucose, glutamine, and asparagine on the basis of partial least-squares regression analysis of near-infrared single-beam spectra covering the 5000–4000−cm–1 (2000–2500-nm) spectral range. Models are constructed with both raw and digitally Fourier-filtered single-beam spectra. Model performance is evaluated and compared with that of analogous models constructed from the corresponding computed absorbance spectra. Five unique data sets are examined corresponding to the measurement of (A) glucose in phosphate buffer with different temperatures, (B) glucose with variable albumin protein levels, (C) glucose with variable triacetin levels, (D) glucose and glutamine in a set of binary mixtures, and (E) glutamine and asparagine in a set of binary mixtures. In all cases, models based on single-beam spectra perform as well as those based on computed absorbance spectra.