bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Historic Papers Using Attenuated Total Reflection Infrared Spectroscopy
Authors: Lang Patricia L. , Cook Jason , Morris Brenda Fuller , Cullison Scott , Telles Scott , Barrett Timothy
Published: October 2003

Previous work has shown that there is a significant correlation between the condition of several historic papers and their gelatin sizing content as determined by wet chemical methods. We have investigated the use of attenuated total reflection infrared spectroscopy in conjunction with principal components regression (PCR) analysis as an improved method to estimate gelatin concentrations as well as other properties on historic papers. From a training set of 25 spectra obtained from handmade papers dated from 1400 to 1800, the results from the PCR analysis indicate that three factors correlate with gelatin concentration with a multiple correlation of 0.8057. Sulfur concentration and potassium concentration also correlate highly with the extracted factors with R values of 0.7937 and 0.8284, respectively. Other properties such as fluorescence, surface pH, date, L* value, and iron concentration significantly correlate with one or more factors as well. The results suggest that the method can facilitate further studies into the relationship between gelatin sizing and paper permanence as well as the relationship between gelatin and other paper components.
Novel Sampling Device for Obtaining Process Near-Infrared Spectra of High-Pressure Gases
Authors: Brown Chris W. , Mangal Amit , Barnett Stanley M.
Published: October 2003

A novel sampling device for making real-time, on-line, near-infrared measurements of high-pressure gases has been constructed and tested. The design makes it possible to measure background spectra between each sample measurement. The position of a floating piston inside a cylindrical cell is controlled by the pressure differences between the sample gas and the background gas. The optical path is transverse to the cylinder axis so that the sample gas is in the beam when its pressure is highest and the background gas is in the beam when its pressure is highest. At 350 psia, a pressure difference of ∼20 psia will drive the piston to the end having the lower pressure and allow the spectrum of the higher pressure gas to be measured. Near-IR spectra of CO2 as a function of pressure and of 15 different natural gas samples were measured and analyzed.
Portable, Low-Cost, Solid-State Luminescence-Based O2 Sensor
Authors: Watkins A. Neal , Wenner Brett R. , Jordan Jeffrey D. , Xu Wenying , Demas James N. , Bright Frank V.
Published: October 2003

A novel sensor for quantifying molecular O2 based entirely on solid-state electronics is presented. The sensor is based on the luminescence quenching of tris(4,7-diphenyl-1, 10-phenanthroline)ruthenium(II) ([Ru(dpp)3]2+) by molecular O2. The sensor involves immobilizing the ruthenium complex within a porous sol-gel-processed glass film and casting this film directly onto the surface of a blue quantum-well light-emitting diode (LED). The ruthenium complex is excited by the LED, the [Ru(dpp)3]2+ emission is filtered from the excitation with a low-cost acrylic color filter, and the emission is detected with an inexpensive silicon photodiode. The sensor response to gaseous O2 and dissolved O2 in water is presented. The sensor exhibits fast response times and good reversibility, and detection limits are 0.5%, 0.02%, and 110 ppb, respectively, for O2 in the gaseous (linear Stern–Vobner and multi-site Stern–Volmer analysis) and aqueous phase. This sensor provides a cost-effective alternative to traditional electrochemical-based O2 sensing and also provides a platform for other optically based sensors.
Optical Fiber-Based Wave Mixing as a Convenient and Sensitive Laser Analytical Tool for Condensed-Phase Analytes
Authors: Nunes Jon A. , Tong William G.
Published: October 2003

A fiber-optic degenerate four-wave mixing (D4WM) probe for the measurement of small absorptions in liquid-phase samples is described. Laser D4WM is a nonlinear laser spectroscopic technique that has proven to be highly sensitive for the detection of trace analytes in condensed-phase media. A significant improvement in the forward-scattering optical arrangement of D4WM is demonstrated by using optical fibers for both laser light input and output. There is considerable flexibility inherent in the design since the system may be used in three configurations: (1) the simplest case of transmitting the signal radiation by optical fiber to the detection electronics, (2) the case of guiding the excitation beams to the analyte by polarization-maintaining optical fibers, and (3) the combination of both. The optical fiber-based D4WM system is shown to be an effective and sensitive laser analytical spectroscopic method for trace analysis, offering advantages such as detection in very small probe volumes, remote and in situ analysis, and convenient and efficient optical alignment enhancements obtained by the use of optical fibers.
Variables Influencing the Precision of Laser-Induced Breakdown Spectroscopy Measurements
Authors: Castle B. C. , Talabardon K. , Smith B. W. , Winefordner J. D.
Published: October 2003

Several factors influence the precision of laser-induced breakdown spectroscopy (LIBS) measurements. This paper reports on the effect of emission signal temporal development, sample translational velocity, number of spectra accumulated, laser pulse stability, detector gate delay, surface roughness, and use of background correction on LIBS precision. The results are presented in two formats: within measurement/shot-to-shot precision (intra-measurement) and between measurement precision (inter-measurement). The data indicate that intra- and inter-measurement precision are optimized under different conditions. The best precision obtained was 0.03%.
Flame Emission Spectroscopy for Equivalence Ratio Monitoring
Authors: Sandrowitz A. K. , Cooke J. M. , Glumac N. G.
Published: October 2003

The dependence of UV-visible emission characteristics in hydrocarbon flames as a function of flame equivalence ratio and total flow rate is examined for low-pressure acetylene/oxygen flames used for materials synthesis and for atmospheric-pressure methane/air flames typically seen in industrial boilers and heaters. In both flames, the OH and CH emission features show significantly different variations with respect to changes in equivalence ratio, while variations with changes in total flow rate are nearly identical. These results suggest that flame emission spectroscopy can be used as a sensitive, on-line process diagnostic for equivalence ratio monitoring in flame reactors.
FT-Raman Spectroscopic Study of Decorated Stained Glass
Authors: Edwards H. G. M. , Tait J. K. F.
Published: October 2003

Two samples of decorated stained glass (14th century and 19th century) from Southwell Minster, Nottinghamshire, U.K. have been examined with the use of Fourier transform (FT)-Raman spectroscopy. The pigment used in both cases has been identified as red ochre, and the potential application of FT-Raman spectroscopy to an important area of conservation and restoration of glass artifacts is demonstrated.
On the Aqueous Vibrational Spectra of Alkali Metal Oxalates
Authors: Hind A. R. , Bhargava S. K. , Van Bronswijk W. , Grocott S. C. , Eyer S. L.
Published: October 2003

Fourier transform infrared attenuated total reflectance and Fourier transform Raman spectra of the series of aqueous alkali metal oxalates—lithium oxalate (Li2C2O4), sodium oxalate (Na2C2O4), potassium oxalate (K2C2O4), rubidium oxalate (Rb2C2O4), and cesium oxalate (Cs2C2O4)—are presented for the first time. Fourier transform Raman spectra of the solid oxalates are also presented for the first time. The solid and aqueous oxalate ions are assumed to possess D2 h and D2 d symmetry, respectively, and the assignment of fundamental vibrational modes is made accordingly. The effect of increasing alkali metal ion concentration on the aqueous spectra of these oxalates is also reported. Spectral changes are explained in terms of the ability of the respective alkali metal cations to interact with the oxalate anion in solution. It is proposed that these differences arise because the alkali metal cations associate with the aqueous oxalate anions to varying degrees, depending upon the nature of the cation. The extent of the binding is found to decrease down the alkali metal series (Li > Na > K > Rb > Cs). Similar results obtained for the tetramethylammonium cation [(CH3)4N+] suggest that it is a softer cation than cesium.
Vibrational Spectroscopic Analysis of Ferroelectric Liquid Crystal MBOPDOB
Authors: He Lei , Yin Zhen , Zhang Ming-Sheng , Shen Ze-Xiang , Chen Hui-Fen
Published: October 2003

Raman spectra of ferroelectric liquid crystal (FLC) D-4-(2-methylbutoxy) phenyl 4-decyloxybenzoate (MBOPDOB) are recorded. All the vibrational modes are assigned, and their vibrational characteristics are studied. It is found that the s-cis and the s-trans conformers of the ester group coexist in the crystal phase at room temperature. By temperature-dependent measurements, the line shape changes due to the transition of the ester group conformation near the crystal-Sm C phase transition point are examined.
FT-IR Internal Reflection Spectroscopy Using Regular Polygonal Internal Reflection Elements
Authors: Lu Y. Q. , Yalamanchili M. R. , Miller J. D.
Published: October 2003

Regular polygonal reactive internal reflection elements (IREs) have been designed and fabricated for Fourier transform infrared (FT-IR) internal reflection spectroscopy (IRS) to study adsorption phenomena at the IRE surface. The geometric and optical features of these polygonal IREs are described with respect to the use of the FT-IR/IRS adsorption density equation. An octagonal internal reflection element of fluorite (CaF2) was prepared with 3 mm sides, and adsorption at the polygon faces was examined by FT-IR/IRS. Adsorption densities thus determined at the surface of the polygonal IRE were found to compare well with those determined at the surface of the parallelepiped IREs of the same material. The utility of regular polygonal IREs, including the advantages and disadvantages, is discussed.
Infrared Transmission and Reflection Absorption Spectroscopy Study on Molecular Orientation of Long-Chain n-Alkane Amide and 2-n-Alkylimidazole Multilayers on Silver and KRS-5 Surfaces
Authors: Gu Yijun , Shi Zheming , Nie Chong-Shi
Published: October 2003

The thin films of cis-oleamide (OlA), steamide (StA), 2-undecylimidazole (UDIM), and 2-nonylbenzimidazole (NBIM) were prepared by spreading their solutions on Ag and KRS-5 substrate evaporating the solvent afterward, with the thickness in the range of 30–100 nm. The amphiphilic molecules in the multilayers were demonstrated to be highly organized by infrared reflection absorption and transmission spectroscopy. The orientation of the head group and the hydrocarbon chain of the amphiphiles in the film has been semiquantitatively evaluated. The C = O group of the amides, as well as the ring plane of imidazole and benzimidazole, has been proved to be parallel to the substrate surface. The CH stretching spectral features of the long hydrocarbon chain of the multilayers are quite different from the reported spectra of the stearate LB multilayer. The orientation of the hydrocarbon chain in the multilayers of StA and UDIM was evaluated to be inclined by about 30° from the substrate surface normal.
Information Depth of Vis-NIR Light in Polyethylene Films Using Transmission and Reflectance Measurements
Authors: Haanstra Willem G. , Hansen Wei , Huys Michel J. G. , Kip Bert J. , Palmen Peter , Roumen Jan , Snieder Marchel , Van De Weerdhof Teun , Wiedemann Sophie , Wortel Vincent A. L.
Published: October 2003

Transmission (400 to 2500 nm) and reflectance spectra (400 to 2200 nm) were recorded from polyethylene films (low-density PE, cryst. 60%, additive free), with a thickness ranging from 0.2 to 8.46 mm. The information depth, defined as the thickness of material that results in the loss of 50% of the light measured as reference, was calculated for both reflectance and transmission geometries. The resulting curves clearly show PE characteristics. For transmission, the information depth varies between ∼100 μm (at 2300 nm) and 830 μm (at 1600 nm). For reflectance, the information depth varies between 0 and 2.5 mm. The reflectance geometry proves to be the better way of measuring through a PE film. The calculated information curve also shows that at PE bands of low to medium strength the contribution of the bulk is very influential. The greater the strength of the PE band, the lower the contribution of the bulk to the spectrum. In case of an inhomogeneous sample, the information depth will reflect the effect of the inhomogeneity on repeated measurements; the weaker the band, the smaller the effect of inhomogeneity will be.
Feasibility of Simultaneous Measurement of Xylene Isomers and other Hydrocarbons in p-Xylene Production Processes Using Near-Infrared Spectroscopy
Authors: Chung Hoeil , Lee Joon-Sik , Ku Min-Sik
Published: October 2003

The feasibility of simultaneous measurement of important components such as o-xylene, m-xylene, p-xylene, ethylbenzene, toluene, aliphatic hydrocarbons, and total C9–C10 aromatic hydrocarbons in the p-xylene production process is investigated. Mixtures of those components were prepared to simulate concentration levels in actual p-xylene processes, and near-infrared (NIR) spectra were collected from mixtures over the spectral range of 1100 to 2500 nm. Even with the very similar spectral features of xylene isomers and other aromatic compounds, the concentrations of each of the components in the mixtures are accurately predicted by using a partial least-squares (PLS) algorithm and show excellent correlation with conventional gas chromatographic analysis. The results clearly demonstrate the possibility of using NIR spectroscopy for monitoring the major components in an actual p-xylene production process for process control and optimization.
High-Power (0.4–1.2 kW) Argon Surface-Wave Plasma for Liquid Solution Analysis
Authors: Besner André , Hubert Joseph
Published: October 2003

Argon surface-wave plasmas produced at power ranging from 0.5 to 1.2 kW are sustained at atmospheric pressure for the study of direct aqueous solution introduction. The plasmas are generally operated at 2450 MHz, but some results are also obtained for a 400 W 27 MHz surface-wave plasma. The emission spectra have been studied between 220 and 940 nm with a medium-resolution spectrometer and with an intensified photodiode array as detector. The effect of the operating parameters (gas flow rate, power) on intensity and signal-to-background noise ratio has been investigated for selected analytes. The detection limits were determined for several analytes (Ba, Ca, Cu, Cr, and Zn) and were found to be comparable to the detection limits obtained with other microwave-induced plasmas.
Application of Mid-Infrared Transmission Spectrometry to the Direct Determination of Glucose in Whole Blood
Authors: Vonach R. , Buschmann J. , Falkowski R. , Schindler R. , Lendl B. , Kellner R.
Published: October 2003

The capability of FT-IR transmission spectrometry was examined for the direct determination of glucose in whole blood without any sample preparation. For these investigations, the whole blood samples were automatically aspirated by a syringe pump into the transmission cell. Infrared spectra were recorded in the 1500–900 cm−1 range. Despite the high water background absorption and the complex blood matrix, significant spectral changes due to different glucose concentrations were observed. Chemometric (partial least-squares) models were applied for the determination of glucose. A standard error of calibration of 13.8 mg/dL was obtained by using a partial least-squares calibration model containing five ranks. The residues for an independent test set were less than 15 mg/dL.
Chemometric Analysis of Diffuse Reflectance-Absorbance Fourier Transform Infrared Spectra Using Rule Induction Methods: Application to the Classification of Eubacterium Species
Authors: Alsberg Bjørn K. , Wade William G. , Goodacre Royston
Published: October 2003

Strains representative of four Eubacterium species were analyzed by using diffuse reflectance-absorbance Fourier transform infrared spectroscopy. To identify important wavenumber regions for the classification of these 22 bacterial isolates, we investigated three rule induction methods and various spectral preprocessing regimes. In this study both univariate and multivariate classification and regression trees (CART) methods and the fuzzy multivariate rule-building expert system (FuRES) method were exploited. It was found that the FuRES method was superior in terms of prediction, whereas the rules proposed by the univariate CART method were easier to interpret in terms of which wavenumbers in the IR spectra were important for bacterial class separation. Scaled and detrended FT-IR spectra and first-order numerical differentiation preprocessing steps were necessary to obtain optimal classification models. Finally, a reduction in the classification error for the CART-based methods was observed by analyzing the compressed B-spline coefficients rather than the original spectra representation. The spectral interpretation of these rules is in agreement with analyses using the uncompressed representation.
Preferential Vaporization during Laser Ablation Inductively Coupled Plasma Atomic Emission Spectroscopy
Authors: Mao X. L. , Ciocan A. C. , Russo R. E.
Published: October 2003

The Zn-to-Cu ratio in brass was measured by laser ablation inductively coupled plasma atomic emission spectroscopy. The influence of laser beam properties (pulse width, wavelength, and power density) on fractional laser ablation was investigated. The behavior of the Zn/Cu ratio vs. laser power density shows that there are different mechanisms influencing ps and ns laser ablation. With the use of a 30 ns pulse duration from an excimer laser, thermal vaporization appears to be the dominant process in the low-power density region. The Zn/Cu ratio approaches stoichiometry at higher power density, but the ablated mass still remains Zn rich. With a 35 ps pulse Nd:YAG laser, a nonthermal mechanism appears to govern the laser ablation process. When a 3 ns Nd:YAG laser is used, both thermal and nonthermal processes exist. For both 3 ns and 30 ps Nd:YAG lasers, stoichiometric ablation can be achieved at higher power densities.
Tracking Nanosecond and Subnanosecond Protein Dynamics On-the-Fly Using Frequency-Domain Fluorescence
Authors: Ingersoll Christine M. , Watkins A. Neal , Baker Gary A. , Bright Frank V.
Published: October 2003

Fluorescence anisotropy and intensity decay experiments on proteins can provide detailed information on biomolecule dynamics and function. However, experiments of this sort are normally performed while the biomolecule is at or near equilibrium. Although information on protein dynamics under equilibrium conditions is extremely important, details about the protein behavior while it is actually undergoing change can provide significantly more insight into the overall protein behavior. Multiharmonic Fourier frequency-domain fluorescence provides a means to acquire fluorescence anisotropy and intensity decay information on a reasonably rapid time scale. As a result, one can potentially track protein nanosecond and subnanosecond dynamical processes on-the-fly as they undergo change(s) during, for example, protein–ligand binding, enzymatic reactions, or antigen/hapten–antibody association. To illustrate the potential of the frequency-domain on-the-fly methodology, we report here on the behavior of a model protein, bovine serum albumin, that has been labeled site-selectively with the fluorescent probe acrylodan (BSA-Ac). Conformational changes in the BSA-Ac are effected by using trypsin or β-mercaptoethanol (BME). BME is a disulfide interchange reagent, and trypsin cleaves and excises from the entire BSA molecule a 21 amino acid peptide segment that contains the covalently attached Ac residue. This paper focuses on the time course of the fluorescence anisotropy and intensity decay kinetics of BSA-Ac as it reacts with trypsin or BME.
Subtraction of the Water Spectra from Infrared Spectra of Acidic and Alkaline Solutions
Authors: Max Jean-Joseph , Chapados Camille
Published: October 2003

The IR spectrum of a sample in acidic and alkaline solutions cannot be retrieved adequately when only the spectrum of pure water is subtracted. After such an operation, some water bands remain in the spectrum, which also has a distorted baseline. An analysis of a series of IR spectra of HCl and NaOH solutions showed that they could be represented by two pairs of eigenspectra, one pair for the acidic solutions and the other for the basic solutions. The fraction of each eigenspectrum of a sample in an acidic or alkaline solution is determined with the 2100 and 3300 cm−1 water bands. After subtraction, no baseline adjustment is necessary. The effectiveness of the method used to subtract the water bands is illustrated with solutions of malic acid at low and high pH.
Phosphorimetric Detection of Polycyclic Aromatic Hydrocarbons on Solid-Phase Extraction Membranes
Authors: Hagestuen Erik D. , Campiglia Andres D.
Published: October 2003

Solid-surface room-temperature phosphorimetry (SS-RTP) has been employed for the determination of polycyclic aromatic hydrocarbons (PAHs) adsorbed on solid-phase extraction (SPE) membranes. Three types of membranes commercially available were tested as solid substrates for phosphorescence emission. The effects of humidity and oxygen quenching were studied on SPEC® membranes. Calibration curves with linear dynamic ranges varying from two to three orders of magnitude were obtained in the presence of 0.05 M sodium dodecyl sulfate and 0.1 M TlNO3. The relative standard deviations of measurements varied between 5 and 10%. The absolute limits of detection were estimated at the ng to sub-ng level. On the basis of the performance of SPE membranes as solid substrates, the potential application of SPE-RTP for the analysis of PAHs is discussed.
Use of 0.0 mm Pathlength Gas Cell to Eliminate CO(g) Absorbance from High-CO-Pressure Solid-State IR Spectra of Nonclassical Metal Carbonyls
Authors: Rack Jeffrey J. , Polyakov Oleg G. , Gaudinski Christine M. , Hammel John W. , Kasperbauer Peter , Hochheimer H. Dieter , Strauss Steven H.
Published: October 2003

A transmission-IR gas cell was constructed from 18%-Ni maraging steel so that two parallel 10 mm diameter × 3 mm thick sapphire windows were held approximately 0.1 mm apart. The cell was engineered to withstand static gas pressures up to 150 atm. When 100 atm CO was placed in the cell, the % transmittance was essentially zero between 2200 and 2080 cm−1 because of the intense v(CO) band centered at 2143 cm−1 (this is an important region of interest for the growing subset of metal carbonyl complexes known as nonclassical metal carbonyls). When the cell was assembled with Nujol or Fluorolube mulls of several microcrystalline copper(I) and silver(I) salts between the windows and CO gas was added to the cell, the gas dissolved in the mulling agents and reacted with the metal salts, but no gaseous CO was observed in the spectrum. New spectral bands were observed that are attributed to unusual metal carbonyl species that are stable only under high CO pressure. A relatively weak band due to free CO dissolved in the mulling agents was detected at 2138–2135 cm−1. The new cell was used to demonstrate that the compound Ag(OTeF5) takes up only one equivalent of CO at 100 atm and that the compound Cu(CF3SO3) takes up two equivalents of CO at 136 atm.
Diffuse Reflectance Infrared Spectra of 4-Nitrobenzoic Acid and 4-Cyanobenzoic Acid Self-Assembled on Fine Silver Particles
Authors: Han Hyouk Soo , Kim Chang Hwan , Kim Kwan
Published: October 2003

Adsorption of 4-nitrobenzoic acid and 4-cyanobenzoic acid on fine silver powders was investigated by diffuse reflectance infrared Fourier transform spectroscopy. It was concluded that both molecules were adsorbed on the surfaces of silver powders as carboxylate, after deprotonation, assuming a perpendicular orientation with respect to the silver surface. In a comparison with the reflection-absorption infrared spectra taken for the same molecules on vacuum-evaporated thick silver films, the usual surface selection rule that applied to flat metal surfaces also seemed applicable to the surface of fine metal particles, as long as the diameter of the particles was near 2 μm. Metal powders with diameters greater than 5μm appeared inappropriate as an adsorbent, however, probably because of particle sizes quite close to the wavelength of the infrared light used.
Optical Constants and Dipole Moment Derivatives of Bromobenzene between 3200 and 400 cm−1 at 25 °C
Authors: Keefe C. Dale , Pittman Janet
Published: October 2003

The optical constants (real and imaginary refractive indices) of bromobenzene were determined at 25 °C via transmission measurements. Experimental absorbance spectra measured on a Nicolet Impact 410 FT-IR were converted to imaginary refractive indices by using methods described in the literature. The real refractive indices were obtained by Kramers-Kronig transformation of the imaginary refractive indices. The complex refractive indices were used to calculate the molar absorption coefficient ( Em) and complex molar polarizability (m) spectra. The integrated intensities and dipole moment derivatives with respect to normal coordinates for the fundamentals were obtained from the areas under the bands in the α“m spectrum. These dipole moment derivatives were compared to those obtained from the spectra of chlorobenzene in the literature. It was found that, in general, the dipole moment derivatives displayed very little dependence on the substituent, even for some of the vibrations for which the wavenumber is substituent sensitive.
Effects of a Membrane Desolvator on the Analytical Performance of a 120 W Helium Microwave-Induced Plasma: Aqueous Desolvation
Authors: Akinbo Olujide T. , Carnahan Jon W.
Published: October 2003

The effect of a flat-sheet membrane desolvator (FSMD) on the analytical performance of a low-power (120 W) He-MIP (helium microwave-induced plasma) is examined. Ultrasonic nebulization with conventional desolvation of an aqueous solution resulted in a dull, red, unstable plasma that was extinguished if the carrier gas flow rate was greater than 1.2 L/min. Using the FSMD with this system resulted in an enhancement of the plasma stability and a significant reduction of the reddish emission from hydrogen atoms. Also, without the FSMD, only weak chlorine emission signals were observed when 1000 ppm aqueous Cl solution was nebulized, but with the FSMD intense chlorine signals were observed with a detection limit of 1.0 μg/mL. Sensitivity improvement factors for Cu, B, P, Cd, and Pb ranged from 1.5 to 20. Greater improvements were seen for “harder to excite” elements.
Determination of Cadmium with a Portable, Battery-Powered Tungsten Coil Atomic Absorption Spectrometer
Authors: Batchelor James D. , Thomas Susan E. , Jones Bradley T.
Published: October 2003

A portable atomic absorption spectrometer is described that is powered by a 12 V car battery. The atomization device is a tungsten coil extracted from a common projector lamp bulb. The coil is housed in a glass cell, and the atomization environment is purged with 10% H2 in Ar (available as a standard commercial welding gas) to prevent oxidation. The detection system is a miniature charge-coupled device (CCD) spectrometer mounted on a PC board. The device is controlled by a laptop computer. Background correction measurements are performed by the near-line method. Aqueous standard solutions provide a Cd detection limit of 3 μg/L (60 pg) for a 20 μL sample volume. Accuracies for the determination of Cd in urine, soil, and stream water are typically better than 90%, with relative standard deviations in the 10% range.
Partial Least-Squares Discriminant Analysis on Autofluorescence Spectra of Oral Carcinogenesis
Authors: Wang Chih-Yu , Chen Chin-Tin , Chiang Chun-Pin , Young Shueng-Tsong , Chow Song-Nan , Chiang Huihua Kenny
Published: October 2003

A partial least-squares (PLS) discriminant analysis on the autofluorescence spectra of oral squamous cell carcinoma based on the cross-validation technique was conducted to discriminate among oral tissues at different cancer development stages. These tissues were obtained from hamsters of DMBA-induced buccal pouch carcinogenesis. The study on the fluorescence spectra of the cancer tissues revealed that 320 nm might be the optimal excitation wavelength, and it was selected for the discriminating analysis. The PLS discriminant plot based on cross-validation showed that tissues of oral carcinogenesis belonging to four clinically important cancer development stages—normal tissues, hyperplasia, dysplasia and early cancers, and frankly invasive cancers—could be classified by using the first two PLS factors that emerged from the fluorescence spectra at 320 nm excitation. The PLS factor loading plots of the first PLS factor of 320 and 360 nm excitations showed that the first PLS factor was correlated to the fluorescent structure changes. This study indicates that further development of the PLS discriminant analysis on the autofluorescence spectra may be useful for developing a simple and efficient discriminating algorithm for the identification of different stages of human oral carcinogenesis.
Determination of the Accuracy and Efficiency of Genetic Regression
Authors: Mosley Matt , Williams Ron
Published: October 2003

Genetic regression (GR) is an application of genetic algorithms to the problem of producing optimal calibration models by wavelength selection. GR has been shown to provide excellent calibration models under many conditions that typically result in poor calibration models with the use of other multivariate techniques. In this study, GR is applied to the calibration of the components of a ternary mixture with the use of near-infrared spectroscopic data. To determine how close GR comes to the true global optimum, a random search of the possible solutions was performed and the distribution of the solutions' predictive abilities determined. Through this study it has been determined that GR is capable of searching through extremely large search spaces and eliminating over 99.9999% of the unsuitable solutions in a matter of minutes. GR is also capable of finding multiple solutions of similar quality, something not available in many other calibration techniques. Comparison with results from partial least-squares (PLS) is also included.
Quantitative Photothermal Radiometric and FT-IR Photoacoustic Measurements of Specialty Papers
Authors: Garcia Jose A. , Mandelis Andreas , Marinova Margarita , Michaelian Kirk H. , Afrashtehfar Shapour
Published: October 2003

Frequency-domain laser infrared photothermal radiometry (PTR) and photoacoustic Fourier transform spectroscopy (FT-IR/PAS) were used for the measurement of the thermophysical properties (thermal diffusivity, α, and conductivity, k) of specialty paper samples with various cotton contents. An improved one-dimensional photothermal model of a free-standing sheet of paper in air that includes both the transmission and backscattering mode was introduced. A high degree of accuracy and reliability was obtained when a multiparameter-fit optimization algorithm was used to examine the transmission and backscattered PTR experimental results. The ability to measure α and its variation, Δα, as a result of the manufacturing process via the PTR technique is invaluable in terms of the quality control of paper products.
Novel Probe for Laser-Induced Breakdown Spectroscopy and Raman Measurements Using an Imaging Optical Fiber
Authors: Marquardt Brian J. , Stratis Dimitra N. , Cremers David A. , Angel S. Michael
Published: October 2003

A fiber-optic probe designed for remote laser-induced breakdown spectroscopy (LIBS), Raman spectroscopy, and Raman imaging has been developed for the microanalysis of solid samples. The probe incorporates both single-strand optical fibers and an image guide and allows atomic emission and Raman analysis of any spot on a solid sample within a 5 mm diameter field of view. The real-time sample imaging aspects of the probe are demonstrated by measuring LIBS spectra from different regions of a granite sample and by measuring the Raman spectra of individual TiO2 and Sr(NO3)2 particles on a soil substrate. The ability to obtain remote Raman images of the TiO2 and Sr(NO3)2 particles on the soil substrate is also demonstrated. In this paper we discuss the design and implementation of the fiber-optic probe for obtaining LIBS spectra, Raman spectra, and Raman images.
Mathematical Model of a Laser-Induced Fluorescence Fiber-Optic Sensor Head for Trace Detection of Pollutants in Soil
Authors: Bünting Uwe , Lewitzka Frank , Karlitschek Peter
Published: October 2003

The efficiency evaluation and optimization of various geometric and material aspects for a fiber-optic sensor head (optrode) are described. For the efficiency evaluation, a mathematical model has been developed and implemented as a computer program. The model allows the variation of several parameters such as diameter and numerical aperture of the optical fibers, their position and orientation in space, and the optical characteristics, as well as the orientation and size of other optical elements used. Peculiarities in manufacture such as oblique polishing of fibers are also taken into consideration. The model was used for the development of a UV laser fluorometer for trace detection of aromatic pollutants in soil. With the other parameters kept constant, the influence of two parameters at a time was calculated and is visualized in a contour plot. A series of such plots is presented, showing how crucial it is to carefully choose the material and geometric properties of an optrode.
Nitrobenzene Detection by One-Color Laser-Photolysis/Laser-Induced Fluorescence of NO (v” = 0–3)
Authors: Daugey N. , Shu J. , Bar I. , Rosenwaks S.
Published: October 2003

Combined one-color laser-photolysis/laser-induced fluorescence methods have been applied to photodissociate nitrobenzene (NB) molecules and to detect the resulting nitric oxide (NO) photofragments. A one-color laser is used to induce photodissociation and detection of NO via the A( v‘ = 0)–X( v” = 0–4) transitions. A strongly wavelength-dependent signature is obtained due to the population of v” = 0–3 of NO. The ratios of the peak heights of the P12 bandhead are ( v” = 0):( v” = 1):( v” = 2):( v” = 3) = 1:0.3:0.1:0.02. A detection limit of ∼500 ppb by weight of NB in air at pressures of 10 and 100 Torr is achieved by monitoring NO X( v” = 2). This is the first attempt to use an excited NO vibrational level for NB detection, and the method can be extended to detection of other nitro compounds. It has the advantage that background of ambient ground-state NO is precluded.
Raman Spectrum of β-Carotene Using Laser Lines from Green (514.5 nm) to Near-Infrared (1064 nm): Implications for the Characterization of Conjugated Polyenes
Authors: Parker Stewart F. , Tavender Susan M. , Dixon N. Michael , Herman Henryk , Williams Kenneth P. J. , Maddams William F.
Published: October 2003

We have studied the Raman spectrum of β-carotene using excitation wavelengths from visible (514.5 nm) to near-infrared (1064 nm). Qualitatively, the spectrum appears independent of the choice of excitation wavelength, although this is not true in detail; in particular, the ratio of the intensities of the νC-C and νC=C fundamentals to their overtones and combinations varies with the excitation wavelength. The inelastic neutron scattering spectrum shows no evidence for unusual dynamics in this system, and the UV/vis/NIR spectrum shows that there are no allowed electronic transitions from the ground state beyond ∼700 nm. These observations provide strong evidence for the existence of a different mechanism for the enhancement of the bands. Indirect evidence suggests that, with these longer excitation wavelengths, the intensities of the νC-C and νC=C peaks are at least two orders of magnitude smaller than those from resonance enhancement with the use of excitation into the visible absorption bands. The implications for the characterization of polyenes in polymers are discussed.
Resolving Optical Constants from Reflectance of Liquids in the UV-Visible Range
Authors: Räty Jukka A. , Vartiainen Erik M. , Peiponen Kai-Erik
Published: October 2003

Reflection spectra of liquids were measured in the UV-visible spectral range with the use of a recently developed reflectometer. The complex refractive index of two solutions, lignin and red food color, both diluted in water, were investigated. For the first time a maximum entropy model was applied in recovering complex reflectivities from non-normal incidence reflectance spectra of liquids. The optical constants in the UV-visible range were then resolved by Fresnel's equations.
Characterization of Hazardous Aqueous Samples by Near-IR Spectroscopy
Authors: Espinoza Luis H. , Lucas Donald , Littlejohn David
Published: October 2003

We describe the application of near-infrared spectroscopy to determine the chemical composition of aqueous samples that simulate hazardous wastes at the DOE Hanford site. Surrogate liquid mixtures are prepared with compositions similar to the actual Hanford liquid wastes. We demonstrate a standard error of precision of approximately 0.06 M for NaNO3 and NaNO2, 0.006 M for Na3HEDTA, and 0.009 M for Na2CO3 by using a 1 mm pathlength and approximately 1 min collection time in the 9000–5400 cm−1 (1.11–1.85 μm) region. Even though most of these electrolytes do not possess characteristic near-infrared bands suitable for quantitative analysis, the use of partial least-squares multivariate calibration makes it possible to correlate spectral differences, based on perturbations in the near-IR water spectrum, and determine each component concentration. The effects of the electrolytes and temperature on the water spectrum are discussed.
Total Organic Carbon Content in Aqueous Samples Determined by Near-IR Spectroscopy
Authors: Espinoza Luis H. , Lucas Donald , Littlejohn David , Kyauk Steven
Published: October 2003

We describe the application of near-infrared spectroscopy with partial least-squares (PLS) multivariate calibration to determine the total organic carbon (TOC) content of aqueous organic samples. We demonstrate a standard error of precision of approximately 0.50 mg/mL for the TOC content in aqueous organic mixtures of Na3HEDTA, Na4EDTA, and acetone. The precision of the simultaneous determination of each component in these samples is 1.66 mg/mL (0.0044 M) for Na3HEDTA, 2.62 mg/mL (0.0063 M) for Na4EDTA, and 0.38 mg/mL (0.0065 M) for acetone. Transmission spectra were collected by using a 1 mm pathlength and approximately 1 min collection time in the 6250–5450 cm−1 (1.60–1.83 μm) region, corresponding to the first C–H overtone band. This analysis procedure was developed to ease TOC determination for hazardous aqueous wastes such as those found at the DOE Hanford site.
Long-Lifetime, Nanosecond Gas-Discharge Light Source Utilizing Automobile Spark Plugs as Lamp Electrodes
Authors: Komatsu Toshiyuki , Araki Tsutomu , Scheeline Alexander
Published: October 2003

We describe the construction and emission characteristics of a gas-changeable and gap-adjustable pulsed light source that produces high-repetition-rate pulsed UV light of nanosecond duration. Automobile spark plugs have been used as the electrodes to extend electrode lifetime and to facilitate maintenance. Stable light pulses of 0.8 ns to 4 ns width are generated when using air, nitrogen, or argon as the discharge gas. Appreciable heterogeneity in the distribution of emission intensity and its onset timing along the discharge gap was observed. The lifetime of the electrode up to 1010 discharge firings has been confirmed for nitrogen fill gas.
Re-Examination of the Effect of Aprotic Solvents upon the Fundamental Vibrational Peak of the Carbonyl Group in 1,1,3,3-Tetramethylurea
Authors: Kolling Orland W.
Published: October 2003

The 1650 cm−1 IR absorption band for the fundamental vibration of the C=O group in tetramethylurea (TMU) exhibits a substantial solvent-induced shift in polar and nonpolar aprotic solvents at 298 K. Earlier studies have rationalized the max(C=O) shifts in terms of the empirical Gutmann acceptor numbers (ANs) for the solvents or the Kirkwood parameter in dielectric permittivity. With a larger set of test data, other reaction field models are now compared which incorporate alternative continuum functions as elements in the formulation of an SCRF-MO perturbation description for the aprotic solvent effect upon the max(C=O) of TMU. The magnitude of the band shift appears to depend on both the solvent dipolarity and solvent polarizability, with the first being the dominant factor in the more reliable model.
Laser Ablation Mass Spectroscopy of Nineteenth Century Daguerreotypes
Authors: Hogan Danel L. , Golovlev Valerie V. , Gresalfi Michael J. , Chaney John A. , Feigerle Charles S. , Miller John C. , Romer Grant , Messier Paul
Published: October 2003

Laser desorption mass spectroscopy has been used to characterize both modern and ∼ 150-year-old daguerreotypes. Such investigations are a necessary prelude to attempts to clean them of tarnish and other contaminants by laser ablation of the surface layers. Both positive- and negative-ion time-of-flight spectra were obtained following YAG laser ablation/desorption at 1064, 532, and 355 nm. Major peaks obtained from several daguerreotypes reveal expected elements from the substrate (Ag, Cu) as well as the developing (Hg) and gilding (Au) processes. Silver clusters (Ag n) may reflect surface desorption of molecules or, alternatively, aggregates formed in the ejection process. Silver sulfide molecules observed from old daguerreotypes are the signature of the tarnishing process.
Far-Ultraviolet Excited Laser-Enhanced Ionization Spectrometry of As, Se, Cu, and Sb in Air/Acetylene and Ar/O2/Acetylene Flames
Authors: Elwood S. A. , Chekalin N. V. , Ezer M. , Pacquete H. L. , Swart D. J. , Simeonsson J. B.
Published: October 2003

Laser-enhanced ionization (LEI) measurements of As, Se, Sb, and Cu in air/acetylene and Ar/O2/acetylene flames are reported. The use of far-UV excitation wavelengths to perform one- and two-step LEI excitation from the ground states of As, Se, and Sb is reported for the first time. Significant ionization background signals are observed for far-UV excitations in the air/acetylene flame, but are reduced by substituting an (80:20) Ar/O2 mixture for air as the flame oxidant. The sensitivities of the individual LEI techniques are also increased by the Ar/O2 gas substitution. The limits of detection for As, Se, Sb, and Cu are 30, 0.5, 9 and 2 ng/mL, respectively, and compare favorably with previous LEI reports. Due to the poor atomization characteristics of As and Se, the utility of hydride generation (HG) sample introduction with LEI detection has been explored. Although high sensitivity has been observed for the HG-LEI approach, limits of detection were not evaluated due to nonlinear responses of the signals with respect to analyte concentration.
Phosphor Thermometry in Combustion Applications
Authors: Vander Wal Randall L. , Householder Paul A. , Wright Theodore W.
Published: October 2003

A new approach for phosphor-based temperature determination is presented. This method is based on comparison between the spectrally resolved phosphorescent emission and a database of spectra collected at a series of temperatures. Applications of two phosphor materials, Gd2O2S: Tb and Mg4(F)GeO6: Mn, possessing different and complementary temperature sensitivities are illustrated. Efficient and accurate comparison is demonstrated between application and calibration spectra with the use of a custom program featuring a general regression neural net algorithm. With this approach, single laser-pulse, spatially resolved measurements are demonstrated. Applications of the technique reported here include measurements of the surface temperature of a thermophoretic sampling probe, the surface temperature of a porous burning solid, wick surface temperatures of supported diffusion flames of acetone, heptane, and decane, and the cellulose pyrolysis and char oxidation temperatures associated with flame spread across a thermally thin fuel at 300 and 700 Torr air pressure.
Improvements in Quantitative Analysis of Steel Composition by Laser-Induced Breakdown Spectroscopy at Atmospheric Pressure Using an Infrared Nd:YAG Laser
Authors: Aragón C. , Aguilera J. A. , Peñalba F.
Published: October 2003

The experimental conditions and procedure for quantitative analysis of steel by laser-induced breakdown spectroscopy in argon at atmospheric pressure using an infrared Nd:YAG laser have been studied. Satisfactory analytical results have been obtained for the determination of C, Si, Cr, and Ni contents in low-alloyed steels. The lens-to-sample distance is shown to be a relevant parameter, which can be selected at each pulse energy to enhance the line intensities and the repeatability of measurements. A higher precision has been obtained for line-intensity ratios (0.9–2.5% relative standard deviation for concentrations higher than 0.1%) than for absolute intensity measurements. The calibration curves for all the elements have correlation coefficients above 0.999. Detection limits are in the range 6–80 ppm.
Solid-State Tunable kHz Ultraviolet Laser for Raman Applications
Authors: Zhao Xiaojie , Chen Ruopian , Tengroth Charbel , Spiro Thomas G.
Published: October 2003

Performance characteristics are described for a kilohertz solid-state laser source for resonance Raman spectroscopy. Narrow line excitation in the 205–230 nm region is provided by quadrupling a titanium: sapphire laser which is pumped by the second harmonic of a Q-switched YLF laser. The combination of tunability, narrow line, high average power, and good stability makes this laser suitable for ultraviolet resonance Raman (UVRR) applications. UVRR spectra of hemoglobin, excited at 229 nm, are as high in quality as those produced by continuous-wave intracavity frequency-doubled Ar+ laser excitation. Raman excitation profiles are reported for aromatic acids in aqueous solution and in hemoglobin.
Surface Enhancement Factors for Ag and Au Surfaces Relative to Pt Surfaces for Monolayers of Thiophenol
Authors: Taylor Chad E. , Pemberton Jeanne E. , Goodman Gary G. , Schoenfisch Mark H.
Published: October 2003

Raman signal intensities from the 997 cm−1 ring breathing mode of thiophenol monolayers adsorbed at Ag, Au, and Pt surfaces were employed for determination of absolute surface enhancement factors (SEFs). Unlike previous estimations of SEFs, these SEFs are determined by referencing the surface-enhanced Raman scattering (SERS) intensities to the unenhanced Raman scattering at Pt surfaces. The surfaces studied include those commonly prepared in a laboratory ambient and those prepared in vacuum. Surfaces prepared in ambient include polycrystalline Ag electrochemically roughened by an oxidation-reduction cycle (ORC), mechanically polished (MP) polycrystalline Ag, chemically polished (CP) polycrystalline Ag, Ag (111), MP polycrystalline Au, and MP polycrystalline Pt. Vacuum environment surfaces include coldly deposited Ag films (cold Ag) and room temperature-deposited (RT) “thick” Ag films. Each of these thiophenol/metal systems was sampled with an excitation wavelength (λex) of 514.5 nm; MP Au surfaces were also studied with λex of 720 nm. SEFs of 2.0 × 104 for ORC Ag, 5.3 × 103 for MP Ag, 160 for cold Ag, 64 for MP Au720 (λex = 720 nm), 69 for Ag (111), 39 for CP Ag, 7.9 for RT “thick” Ag, and 2.2 for MP Au514.5 (λex 514.5 nm) are observed relative to the SEF of MP Pt, which is assigned as 1. For practical purposes, the significance of the magnitudes of these SEFs is discussed in terms of estimated surface Raman limits of detection (LODs).