bluuebunny/crossref_metadata_2025 huggingface dataset:
Isocyanate-Wood Adhesive Bond
Authors: Weaver F. William , Owen Noel L.
Published: May 2005

We have used infrared spectroscopy to study the reaction between phenyl isocyanate and glucose, cellulose, lignin, and wood. In the latter instance we have investigated oven-dried wood, wood at its fiber saturation point, and wood at 19% and 7% moisture levels. Our results show that the isocyanate reacts with all these entities, but that its reaction with water is quicker than with any of the other hydroxyl-containing compounds, and when water is present the water-isocyanate reaction dominates all others. Lignin was found to react more readily than any of the sugar derivatives. In oven-dried wood, the presence of strong new absorptions at 1712 and 1694 cm−1 (indicative of a carbamate group) is evidence of a direct chemical bond between the isocyanate and the wood polymer structure. We have also studied the reaction between 4,4′-diphenylmethane diisocyanate (MDI)—a commercially used adhesive—with wood flour at various levels of moisture content (MC), and the infrared spectra again support the presence of a wood-isocyanate bond for oven-dried wood and for wood at 7% moisture content. For wood at higher moisture content levels, our infrared results suggest that the isocyanate reacts with the water in preference to the wood polymers.
Investigations of a Magnetically Enhanced Grimm-Type Glow Discharge Source
Authors: Heintz Mark J. , Mifflin Kimra , Broekaert Jose A. C. , Hieftje Gary M.
Published: May 2005

The application of a magnetic field to the Grimm glow discharge lamp in order to enhance its sputtering rate and emission characteristics for optical emission spectrometry was investigated. A Nd-Fe-B magnet was placed behind samples of copper and Monel 400 (a Cu-Ni-Fe alloy) having thicknesses of 1.0–1.5 mm. The sputtering rates (at 1000 V in argon at 4 Torr) for copper could be increased from 100 to 200 μg/min under the influence of the magnetic field. The noise behavior of the atomic emission was found to be influenced slightly by the application of the magnetic field. For the nonresonance Cu(I) line emission at 282.4 nm, an increase in intensity occurred in accordance with the increase in sputtering rate, whereas for resonance lines [Cu(I) 324.7 nm in the case of copper samples and Cr(I) 425.7 nm for Monel 400 containing 0.06% (w:w) Cr], a drop in the atomic emission was found upon application of the magnetic field. This result is thought to be due to self-absorption, which has been shown to occur in a Grimm-type glow discharge source.
Efforts to Quantify Changes in Near-Infrared Spectra Caused by the Influence of Water, pH, Ionic Strength, and Differences in Physical State
Authors: Reeves James B.
Published: May 2005

The application of near-infrared spectroscopy to high-moisture samples has shown that the accuracy does not match that found for dried materials. The objective of this work was to attempt to quantify the effects of water, pH, ionic strength, and differences in physical state on near-infrared spectra with the use of model compounds. Spectra were compared by regression analysis of second derivatives after spectral subtraction of water. Spectra from 4900 to 4100 cm−1 at a resolution of 4 cm−1 were examined. Regression results showed spectra to be more similar among amorphous sugars and among dissolved sugars than among crystalline sugars. Also, spectra of amorphous sugars were statistically more similar to spectra of dissolved sugars than to spectra of crystalline sugars. While the spectra of one dissolved or amorphous sugar were statistically similar, this was not true for amino acids. Spectra of amorphous amino acids were similar to those of crystalline forms and neither were similar to those of dissolved forms. Spectrally, polymeric carbohydrates appeared very similar to one another when dry and behaved like amino acids when wet. Finally, efforts to directly relate these findings to near-IR spectroscopy calibration problems will require further research.
Performance and Selected Applications of an Acousto-Optic Tunable Filter Near-Infrared Spectrometer
Authors: Hühne Martin , Eschenauer Ursula , Siesler Heinz W.
Published: May 2005

The design and applications of a near-infrared (near-IR) spectrometer with an acousto-optic tunable filter (AOTF) as monochromator and light fiber optics are described. The aim of this spectrometer is rapid product and reaction control via remote sensing and chemometric data evaluation. Its application and performance are illustrated by the determination of the water content of acetone and by the contact-free temperature measurement of an aqueous solution.
Excitation Profile of the Resonance Raman Effect of Uranyl Nitrate in Dimethyl Sulfoxide
Authors: Ohwada Ken , Takahashi Akira , Fujisawa Ginji
Published: May 2005

The resonance Raman spectra of uranyl nitrate in dimethyl sulfoxide (DMSO) were measured at room temperature, with the use of ten output lines (528.7, 514.5, 501.7, 496.5, 488.0, 476.5, 472.7, 465.8, 457.9, and 454.5 nm) of an argon-ion laser. The excitation profile of the resonance Raman effect has been obtained by plotting the relative intensities of the uranyl symmetric stretching vibration at 835 cm−1 against the laser exciting wavelengths. It has been found that the observed excitation profile of the uranyl symmetric stretching vibration resembles the vibronic structure of the electronic absorption spectrum. Also, the excitation profile obtained is briefly discussed in relation to the theory developed by J. Tang and A. C. Albrecht.
Quantitative Analysis of Individual Sugars during Starch Hydrolysis by FT-IR/ATR Spectrometry. Part II: Influence of External Factors and Wavelength Parameters
Authors: Bellon-Maurel Véronique , Vallat Céline , Goffinet Darrell
Published: May 2005

Earlier experiments have confirmed the suitability of Fourier transform infrared attenuated total reflectance (FT-IR/ATR) spectroscopy for monitoring sugar production from starch hydrolysis. However, in order to confirm the suitability of this technique for an industrial use, the influence of external factors (proteins, salts, temperature) on the prediction, as well as the influence of wavelength parameters, must be evaluated. This paper shows that proteins and salts, which occur in low concentrations in sugar solution before purification, have virtually no influence on the detection of sugar. However, sample temperature, already a very important factor in the industrial hydrolysis of starch, does have an influence upon spectral measurements. This influence would therefore affect the prediction ability of a model made at a single temperature. A proven solution to the influence of temperature is to establish a model which takes into account the range of temperatures that occur during the hydrolysis process. Variations in wavelength parameters also have been shown to significantly affect prediction ability.
Quantitative Analysis of Individual Sugars during Starch Hydrolysis by FT-IR/ATR Spectrometry. Part I: Multivariate Calibration Study—Repeatibility and Reproducibility
Authors: Bellon-Maurel Véronique , Vallat Céline , Goffinet Darrell
Published: May 2005

This paper discusses the use of Fourier transform infrared (FT-IR) spectroscopy coupled with an attenuated total reflectance (ATR) accessory as applied to the quantification of individual sugar concentrations (glucose, maltose, maltotriose, and maltodextrines) in real mixtures extracted during starch hydrolysis. Solutions studied contained dry matter ranging between 250 and 300 g/kg. Glucose and maltose were detected with the required precision, but not maltotriose or maltodextrines. The measurements are fairly repeatible, and predictions are reproducible.
High-Spatial-Resolution OH Rotational Temperature Measurements in an Atmospheric-Pressure Flame Using an Indium-Based Resonance Ionization Detector
Authors: Petrucci Giuseppe A. , Imbroisl Denise , Guenard Robert D. , Smith Benjamin W. , Winefordner Jame D.
Published: May 2005

The use of a resonance ionization photon detector (RID) is described for the measurement of flame temperatures with a spatial resolution of less than 100 μm. The detector, based on the two-step excitation of indium atoms, with subsequent collisional ionization, was used to record rotational excitation scans of OH in an atmospheric-pressure acetylene/air flame. The OH excitation spectra were recorded by scanning an “excitation” laser in the A2σ+ ← X2II i (1, 0) vibronic band in the wavelength range, 281–288 nm, while simultaneously illuminating the same flame region with the “detection” laser, tuned to the 6 p2 P3/2 → 10 d2. D5/2 excited-state transition of In at 786.44 nm. The excitation and detection laser beams were made orthogonal in the flame, defining the resolution to be limited by the waist of the excitation beam (100 μm), whose diameter was always smaller than the detection laser beam. A temperature profile of the flame is recorded with the use of both the RID approach and a more conventional laser-induced fluorescence (LIF) approach for comparison. A more structured temperature profile is recorded with the RID owing to its high spatial resolution, whereas the LIF method, which is inherently a line-of-sight method, produces a rather featureless temperature distribution across the flame. Anomalously high flame temperatures were recorded at the flame edge with the RID. The cause of these high flame temperatures has not been determined.
Complex Refractive Index Determination of Bulk Materials from Infrared Reflection Spectra
Authors: Yamamoto Kiyoshi , Masui Akio
Published: May 2005

Kramers-Kronig analysis is applied to extract complex refractive indices of an isotropic single crystal, ceramics, glasses, and organic materials from their infrared external reflection spectra measured near the normal angle of incidence. It is demonstrated that this technique is versatile and can obtain complex refractive indices of materials. The great advantage of this technique is that a wide variety of materials (organic to inorganic, solid to liquid) can be analyzed and that no prior information is required for the analysis. The calculation procedure of the principal integration in Kramers–Kronig analysis of reflection spectra is also presented.
Constant-Fraction Discrimination/Boxcar Integrator for Plasma Source Time-of-Flight Mass Spectrometry
Authors: Yang Pengyuan , Myers David P. , Li Gangqiang , Hieftje Gary M.
Published: May 2005

A constant-fraction discrimination (CFD) system has been combined with a boxcar integrator for detection in inductively coupled plasma/time-of-flight mass spectrometry. The discriminator provides gating logic for the boxcar integrator when an incoming ion signal occurs, but discriminates against electronic or background noise of lower amplitude. As a result, the combination can effectively reject noise and accumulate analyte signal, rather than relying on an averaging process to reduce noise levels. The signal-to-noise ratio is therefore enhanced in this operation compared with the conventional boxcar method. The dynamic range of the detection system is at least five orders of magnitude.
Real-Time, Mid-Infrared Spectroscopic Imaging Microscopy Using Indium Antimonide Focal-Plane Array Detection
Authors: Lewis E. Neil , Levin Ira W.
Published: May 2005

A different approach toward mid-infrared spectroscopic imaging microscopy is introduced in which instrumentation is designed about an InSb multichannel, focal-plane array detector and a variable-bandpass dielectric filter. The system may be configured for either macroscopic or microscopic applications, and high-fidelity, chemically specific images may be acquired in real time. With the dielectric filter used in this assembly, continuous tuning is provided for the infrared 4000–2320 cm−1 spectral region with spectral resolutions of approximately 35–18 cm−1 at the extremes of this wavelength interval. The functioning of the imaging microscope is demonstrated with samples including polystyrene microspheres, preparations of lipids and an amino acid embedded in KBr disks, and a tissue sample derived from a coronal slice of a monkey cerebellum.
Fiber-Optic/GRIN Lens Couples for Use in Chemical Spectroscopy
Authors: Landis David A. , Seliskar Carl J.
Published: May 2005

Multimode optical fiber-graded index (GRIN) lens couples are modeled with the use of an algorithm which quantitatively traces light paths through the optical elements. The effects of the variation of optical fiber core size, GRIN lens length (pitch), fiber-optic/GRIN lens separation, and wavelength are quantitatively demonstrated. Chromatic effects specific to™ GRIN lens couples are evaluated for the near-UV to near-infrared spectral region. In general, GRIN lens couples are found to be superior to equivalent ball lens couples for spectroscopic applications. A simple example application of the multimode fiber-optic/GRIN lens couple in remote chemical spectroscopy is presented.
Performance Analysis of an Integrated Process Raman Analyzer Using a Multiplexed Transmission Holographic Grating, CCD Detection, and Confocal Fiber-Optic Sampling
Authors: Everall Neil , Owen Harry , Slater Joe
Published: May 2005

The performance of an integrated turn-key on-line Raman spectrometer based upon a multiplexed transmission holographic grating, holographic laser rejection filters, and a charge-coupled-device (CCD) detector is described and compared with a laboratory-based research-grade FT-Raman spectrometer. Data for the dispersive system were acquired with a noncontacting, confocal dual-fiber probe of up to 100-m length, with Raman shifts down to 50 cm−1 and no apparent fiber background features. Despite the fact that the FT-Raman system was directly coupled to the sample (i.e., not through fibers), the sensitivity of the dispersive system was almost three orders of magnitude greater for equivalent incident laser powers and accumulation times. The potential for performing multivariate calibrations with the dispersive equipment was also investigated. With samples of known density, it was possible to produce a partial least-squares calibration for poly(thylene terephthalate) (PET) density with a precision of 0.002 g cm−3, with the use of a two-factor model. This precision compared favorably with previous calibrations using FT-Raman data. The effect of changing the f-number of the collection optics of the fiber probe head (to allow variation in the working distance) was also examined. It was found that, for transparent samples, the f-number could be changed by a factor of three without greatly affecting the Raman signal intensity, whereas for an opaque solid increasing the f-number greatly reduced the detected intensity. The reasons for this difference are discussed
New Technique for ATR/FT-IR Spectra Measurements of Adsorbed Layers on a Solid-Phase/Liquid Boundary
Authors: Chernyshova I. V. , Tolstoy V. P.
Published: May 2005

An ATR/FT-IR technique is described which employs thermoplastic halcogenide glass with a low melting point to bring a solid plate (or a film) into optical contact with the ATR element. The sensitivity of the ATR/FT-IR method with one reflection was one-tenth of a surface monolayer. It was achieved by obtaining spectra at critical angles of incident radiation. Such an approach allows the study of in situ solid/liquid interfaces, where a solid may be relatively opaque over the IR range. The intensity and frequency of the ATR band δs(H2O) are found to depend strongly on wetting properties of the surface. Monitoring relative hydrophobicity/hydrophilicity of the surface in situ simultaneously with analysis of the surface composition is valuable for numerous technologically significant areas, such as flotation, synthesis of coatings with definite wetting properties (water-proof or water-attractive), adhesion, etc. This technique permits the recording of spectra in the kinetic and static regimes and the study of different crystallographic planes. The relative inertness of the halcogenide glass makes it possible to apply a wide range of potentials to the sample (or pH of solutions). Therefore, the technique may be applied in electrochemistry or catalysis. The spectroscopic data obtained by means of this approach for galena/xanthate and pyrite/xanthate systems in borate buffer (pH 9.2) were shown to agree satisfactorily with previous flotation results.
Gas-Sampling Glow Discharge for Optical Emission Spectrometry. Part II: Optimization and Evaluation for the Determination of Nonmetals in Gas-Phase Samples
Authors: Pereiro Rosario , Starn Timothy K. , Hieftje Gary M.
Published: May 2005

A new gas-sampling glow discharge (GSGD) is evaluated for the continuous determination of C, F, Cl, and S in molecular gases and organic vapors by optical emission spectrometry, with the use of helium as the discharge gas. Discrete aliquots of the sample are introduced into an exponential dilutor and carried by the support gas through a silica capillary tube and into the glow discharge. Radiation from the plasma source is viewed axially. The effects of plasma operating parameters such as power and pressure are studied, and emission lines of C, F, Cl, and S measured. Analytical performance is evaluated under conditions found to be optimal for each element, as well as under compromise conditions chosen for the simultaneous detection of all four elements. In both cases, detection limits in the low ng/s range, good precision (RSD < 5%), and dynamic ranges of 2–3 decades were observed for the four elements. The utility of this He–GSGD for the determination of elemental ratios in organic compounds is also investigated.
Influences on Concentration Measurements of Liquid Aerosols by Laser-Induced Breakdown Spectroscopy
Authors: Poulain Dana E. , Alexander Dennis R.
Published: May 2005

Results are presented for laser-induced breakdown spectroscopy (LIBS) as a method for measuring salt concentrations in seawater aerosol droplets. An excimer laser, operating at high pulse energy with KrF gas (λ = 248 nm) produces laser-induced breakdown plasmas in an aerosol spray. Emission lines of Na and H are monitored with an optical multichannel analyzer to characterize the plasma spatially and temporally. Studies of temporally resolved atomic line emissions from the plasma determine the optimum time for gating of the detector to be 2–4 μs after the excimer laser pulse arrives in the probe volume. Spatially resolved measurements of atomic emission line intensities are studied by positioning a stream of monodisperse droplets at various locations relative to the measurement probe volume. The electron temperature of the plasma is estimated to be 12,600 ± 4600 K, averaged over 1700 measurements during a 100-ns interval 2 μs after breakdown. Calibration curves are presented relating the Na(I) 589-nm to Hα 656.3-nm intensity ratio as a function of Na concentration, ranging from 100 to 10,000 ppm. Limits of detection for Na by the current method under the experimental conditions are estimated to be approximately 165 ppm for monodisperse sprays and 925 ppm for one case involving a polydisperse spray. Droplet diameter strongly influences the observed emission intensity ratio.
Application of the Kubelka-Munk Theory to Thickness-Dependent Diffuse Reflectance of Black Paints in the Mid-IR
Authors: Gunde M. Klanjšek , Logar J. Kožar , Orel Z. Crnjak , Orel B.
Published: May 2005

The Kubelka-Munk theory is applied to the thickness-dependent diffuse reflectance of black-painted samples in the mid-IR. The calculated absorption and scattering coefficients are wavenumber-dependent. The reflectance of the nonideal backing also shows spectral features, which is attributed to the reflections from the boundary surface between the scattering medium and the substrate. The spectral dependence of scattering penetration depth is caused by the scattering and absorption processes. At some wavenumbers, the diffuse reflectance is independent of layer thickness, because of particular values of the parameters of the applied theory. The application of the Kubelka-Munk function is discussed.
Classification of Green Coffees by FT-IR Analysis of Dry Extract
Authors: Dupuy Nathalie , Huvenne Jean Pierre , Duponchel Ludovic , Legrand Pierre
Published: May 2005

Principal component analysis (PCA) of infrared spectra has been used as a classification method for the green beans of coffee from various origin. Before spectral acquisition, sampling methods were tested for 45 samples, and we chose dry extract of water-soluble compounds on SiCaF2 supports. After PCA of the first derivatized spectra, the first four loadings were examined. The scores of the second principal component appear to be directly correlated by their sign to the species arabica or robusta. This result allows an easy classification. In the same way, the pigmentation is well characterized into two groups on the scattergram of the samples with respect to the PC1 and PC3 components. Another feature of this method is that the analysis of the spectral data in terms of residual variance separate components which are correlated with properties. This approach provides assistance in the interpretation of infrared spectra of complex mixtures.
Screening Pap Smears with Near-Infrared Spectroscopy
Authors: Ge Zhengfang , Brown Chris W. , Kisner Harold J.
Published: May 2005

A rapid method for the analysis of Pap smears has been developed with the use of near-infrared spectroscopy. Spectra of Pap smears from 50 female patients including 30 with normal cells, 9 with atypical cells, and 11 with cervical cancer were measured in the near-IR region of 4000 to 10,000 cm−1. Both the original spectra and the second-derivative spectra of Pap smears were subjected to data analysis. The malignant samples displayed abnormal spectra compared with the corresponding normal cervical samples; the atypical samples have spectral features characteristic of both normal and abnormal samples. With the use of principal component analysis (PCA) and discriminant analysis, the samples were grouped in patterns that were consistent with clinical analysis. Since obtaining near-infrared spectra of human tissues is a rapid and inexpensive process, the results suggest that the near-infrared spectra of human tissues may be of diagnostic value for cancer diagnosis.
FT-IR Analysis of the Laser-Induced Dissociation of Methylphosphonic Difluoride
Authors: Stanley Ann E.
Published: May 2005

The output of a continuous-wave carbon dioxide laser was used successfully for the dissociation of methylphosphonic difluoride. End product analysis using Fourier transform infrared spectroscopy revealed that the phosphorus-to-carbon bond was cleaved, yielding the products methane, ethene, ethyne, hydrophosphoryl difluoride, and a mixture of phosphorus compounds. These results are presented and discussed. The dissociation was optimized. A reaction mechanism of the dissociation is suggested.
Quantitative Gas Analysis with FT-IR: A Method for CO Calibration Using Partial Least-Squares with Linearized Data
Authors: Bak Jimmy , Larsen Anders
Published: May 2005

Calibration spectra of CO in the 2.38–5100 ppm concentration range (22 spectra) have been measured with a spectral resolution of 4 cm−1, in the mid-IR (2186–2001 cm−1) region, with a Fourier transform infrared (FT-IR) instrument. The multivariate calibration method partial least-squares (PLS1) was used to model the CO calibration spectra in order to improve the sensitivity and to flag possible outliers in the prediction step. The relation between the absorbance values and concentrations was strongly nonlinear. This result was caused mainly by the low spectral resolution of the instrument. To improve the model predictions, we have linearized the data prior to making the model calculations. The linearization scheme presented here simplified the data pretreatment, because the function needed to linearize the data might be approximated by co-absorbance peak areas representing the concentrations. The integrated absorbance areas, rather than the concentration values, were used as input to the PLS algorithm. A fifth-order polynomial was used to calculate the concentrations from the predicted absorbance areas. The PLS algorithm used on the linearized data reduced the number of factors in the calibration model. Our results reveal that the calibration model based on the linearized data had a high concentration prediction accuracy throughout the entire concentration range.
SNR Enhancement and Deconvolution of Raman Spectra Using a Two-Point Entropy Regularization Method
Authors: Greek L. Shane , Schulze H. Georg , Blades Michael W. , Bree Alan V. , Gorzalka Boris B. , Turner Robin F. B.
Published: May 2005

A new method for Raman signal recovery, the two-point maximum entropy method (TPMEM), based on a regularization method using two-point entropy is presented. The method can be used for signal-to-noise ratio (SNR) enhancement in very low SNR measurements or for deconvolution, in order to remove the effects of the instrumental line shape on the measured spectrum. Unlike most SNR enhancement schemes, TPMEM requires no filter parameters and no a priori knowledge of the expected signal. A rigorous test on a randomly produced set of convolved and/or noise-corrupted simulated Raman spectra is presented in order to validate the method and compare it to Savitzky-Golay filtering and the maximum entropy method. The method is evaluated on the basis of the root mean square (rms) error and correlation coefficients of the recovered data with the original data, as well as on the basis of SNR improvement, and showed significant improvements in both performance and speed over conventional methods. The method is demonstrated in an application involving fiber-optic-linked Raman and resonance Raman spectroscopy.
Use of Internal Reflectance Infrared Spectroscopy for the in Situ Study of Supported Lipid Monolayers
Authors: Axelsen Paul H. , Braddock W. David , Brockman Howard L. , Jones Craig M. , Dluhy Richard A. , Kaufman Brad K. , Puga Francisco J.
Published: May 2005

An instrument has been developed to acquire polarized attenuated total internal reflection (ATIR) mid-IR spectra of supported monomolecular films in situ at the lipid/water (L/W) interface. The monolayer film is applied to the treated surface of a trapezoidal germanium crystal as it is immersed into the subphase of a specially designed Langmuir-Blodgett trough. This approach offers several advantages over the study of monolayer films at the air/water (A/W) interface by external reflection techniques, including (1) an improved signal throughput and multiple reflections, both contributing to an improved signal-to-noise (S/N) ratio; (2) versatility with respect to the chemical nature of the surface; and (3) the ability to use standard spectral subtraction methods to compensate for absorption of the aqueous subphase. The enhanced sensitivity of this approach facilitates the study of in situ interactions of peptides with fully hydrated lipid membrane surfaces.
Detection of the Engine Anti-Knock Additive Methylcyclopentadienyl Manganese Tricarbonyl (MMT) from Unleaded Gasoline in Soil by Diffuse Reflectance Infrared Fourier Transform Spectroscopy and Mass Spectrometry
Authors: Vreugdenhil Andrew J. , Butler Ian S.
Published: May 2005

Soil samples were washed with dilute solutions of the toxic anti-knock fuel additive methylcyclopentadienyl manganese tricarbonyl (MMT) in hexanes and commercial unleaded gasoline. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was then used to detect the v(CO) modes of MMT, and subsequently 13CO-enriched MMT, in the soil samples. The presence of MMT in the soils was further confirmed by mass spectrometry. Concentrations corresponding to ∼10 ppm Mn in soil could be detected by DRIFTS of the dry samples, and, most interestingly, there was no evidence of significant MMT decomposition over a period of eight months. Apparently, MMT is stabilized by physisorption onto the soils. In the absence of such stabilization, however, MMT undergoes photolytic and thermal decomposition in a matter of minutes. These results suggest the possibility of longer-term environmental problems associated with gasoline spills containing MMT than was previously suspected.
NMR Characterization of Sulfonation Products of Phenylchloroformate with Verification of NOE Effects by Molecular Modeling
Authors: Kwoh David , Kerschner Judith L. , Jensen Arnold , Cece Anthony
Published: May 2005

In the trial scale-up of the sulfonation of phenylchloroformate and subsequent formation of sulfonated phenyl carbonates, samples from the batch process showed a number of unexpected by-products. Because they were suspected to have an unusual ring substitution pattern, phenylchloroformate sulfonation was studied by 1H and two-dimensional nuclear magnetic resonance (NMR) techniques. Distance geometry was used to compute internuclear distances, which were used to substantiate the observation of the nuclear Overhauser effect. The reaction mechanism leading to these by-products is proposed.
Low-Volume Diffuse-Transmittance Fiber-Optic Near-IR Spectrophotometer
Authors: Fong Andrew , Hieftje Gary M.
Published: May 2005

A simple, inexpensive near-IR spectrophotometer is described that employs single fiber-optic strands in a diffuse-transmission geometry. The instrument can examine unusually small sample volumes and offers sufficient throughput to perform multicomponent analyses on diffusely transmitting powdered samples. Control of the effective optical pathlength is found to be critical in obtaining reproducible results when scattering samples are to be analyzed. A pseudo-double-beam arrangement is employed to reduce instrument noise and to set the optical pathlength independently for each sample. Sample sizes of only a few tens of milligrams are required for analysis. The resulting performance is nearly equivalent to that of a commercial reflectance instrument. An average standard error of prediction of 2.77% w/w was obtained for four-component mixtures of benzoic acid derivatives. The single-fiber transmission geometry is shown to be useful also in the near-IR analysis of microliter volumes of liquids. A standard error of cross-validation of 17 mM sodium chloride dissolved in water was achieved.
Principal Component Analysis of Near-Infrared and Visible Spectra: An Application to a XIIth Century Italian Work of Art
Authors: Orlando A. , Picollo M. , Radicati B. , Baronti S. , Casini A.
Published: May 2005

Statistical data processing was performed on the spectra of a painting recorded in the near-infrared (near-IR) and visible (Vis) region by a totally nondestructive method. Results are discussed also in connection with colorimetric analysis.
Spatial Distribution of Radiant Intensity from Primary Sources for Atomic Absorption Spectrometry. Part I: Hollow Cathode Lamps
Authors: Gilmutdinov Albert Kh. , Radziuk Bernard , Sperling Michael , Welz Bernhard , Nagulin Konstantin Yu.
Published: May 2005

The spatial distribution of radiant intensity from hollow cathode lamps used as radiation sources in atomic absorption spectrometry is investigated with a digital photodiode array imaging system. Intensity distribution over the cross section of each lamp is measured for both atomic and ionic lines of the analyte and the filler gas. The shape of the distribution is strongly dependent on the hollow cathode diameter. In small cathodes the distribution has the shape of a paraboloid with maximum intensity at the hollow cathode axis for all of the recorded lines. The intensity distributions of lines emitted from large cathodes are nonparaboloid and in some cases have a minimum at the cathode axis and a maximum concentric to the cathode walls. It is shown that the intensity distribution for a given lamp has practically the same shape for all currents applied. Data on the evolution of the intensity distribution during warm-up of the lamps and under various operating conditions are presented.
Chemical Characterization of Transition Metal Spinel-Type Oxides by Infrared Spectroscopy
Authors: Allen Geoffrey C. , Paul Michael
Published: May 2005

Standard spinels of the type formed during the oxidation of stainless steel surfaces have been analyzed by infrared techniques. Comparison of the spectra for each series of spinels shows that it is possible to identify the stoichiometry and structure of the spinel from its infrared spectrum.
Quantitative Detection of Environmentally Important Dyes Using Diode Laser/Fiber-Optic Raman Spectroscopy
Authors: Gilmore Daniel A. , Gurka Donald , Denton M. Bonner
Published: May 2005

A compact diode laser/fiber-optic Raman spectrometer is used for quantitative detection of environmentally important dyes. This system is based on diode laser excitation at 782 nm, fiber-optic probe technology, an imaging spectrometer, and a state-of-the-art scientific CCD camera. The dyes studied include trypan blue, acid black 1, acid blue 40, and basic blue 7. Detection sensitivities (at rms S/N = 2) ranged from 0.2 ppm (3.24 × 10−7M) for acid black 1, to 25 ppm (4.86 × 10−5M) for basic blue 7.
Near-IR Multiplex Bandpass Spectrometer Utilizing Liquid Molecular Filters
Authors: Fong Andrew , Hieftje Gary M.
Published: May 2005

A simple near-infrared spectrometer is described which uses common liquids as near-IR spectral filters. Each filter substance passes multiple bands of near-IR radiation. This new type of spectrometer offers simplicity, cost advantages, and enhanced throughput. The high throughput is useful for ensuring the high signal-to-noise ratio typically needed for chemometrics. The high throughput also allows the use of longer sample pathlengths. The performance of the spectrometer is demonstrated in the determination of methanol through a 1-cm pathlength of water and in the determination of trace amounts of water in organic solvents such as propylene glycol and dimethyl sulfoxide (DMSO). Best-case detection limits were 0.02% (w/w) methanol in water, 0.0006% water in DMSO, and 0.004% water in propylene glycol.
Improved Calibration for Inductively Coupled Plasma-Atomic Emission Spectrometry Using Generalized Regression Neural Networks
Authors: Catasus Miguel , Branagh Wayne , Salin Eric D.
Published: May 2005

Artificial neural networks have been recently used in different fields of science in applications ranging from pattern recognition to semi-quantitative analysis. In this work, two types of neural networks were applied to the problems of spectral interferences, matrix effects, and the measurement drift in ICP-AES. Their performance was compared to that of the more conventional technique of multiple linear regressions (MLR). The two types of neural networks examined were “traditional” multilayer perceptron neural networks and generalized regression neural networks (GRNNs). The GRNN is comparable to, or better than, MLR for modeling spectral interferences and matrix effects covering several orders of magnitude. In the case of an Fe spectral interference on Zn, the GRNN reduced the error from 81% to 24%, while MLR reduced the average error to only 49%. For matrix effects caused by large backgrounds of Mg (0–10,000 ppm) on Zn, average error was reduced to 55% from 67%. In the case of combinations of spectral overlaps and matrix effects, the GRNN reduced average error by approximately 10%. MLR performed poorly on systems involving matrix effects. GRNN is also a very promising tool for the correction of drift caused by fluctuations in power levels, reducing drift over a two-hour period from 2.3% to 0.6%. GRNNs, both by themselves and in multinetwork combinations, seem to be highly promising for the correction of nonlinear matrix effects and long-term signal drift in ICP-AES.
Simultaneous Determination of Rubber Additives by FT-IR Spectrophotometry with Multivariate Calibration
Authors: Blanco M. , Coello J. , Iturriaga H. , Maspoch S. , Bertran E.
Published: May 2005

A new method for the simultaneous determination of vulcanized rubber additives by Fourier transform infrared (FT-IR) spectrophotometry using partial least-squares regression (PLSR) for multivariate calibration was developed. The effect of various wavenumber ranges and the use of the absorbance and first-derivative spectral modes on performance were studied by applying the method to three different sample batches containing several additives in different proportions, all of which were resolved with satisfactory results.
Noninvasive Quantitative Chromium(III) Speciation in Neat Solid Mixtures by Extended X-ray Absorption Fine Structure Spectroscopy
Authors: Lamoureux M. M. , Hutton J. C. , Styris D. L. , Gordon R. L.
Published: May 2005

A procedure that uses extended X-ray absorption fine structure (EXAFS) spectroscopy for quantitative chromium(III) speciation in neat solid mixtures is described. The procedure uses the full, filtered EXAFS, e.g., 4 ≤ k ≤ 12 Å−1, rather than the smaller k-range associated with a single coordination sphere. Concentration is determined by a simple correlation of full, filtered EXAFS of standards with full, filtered EXAFS of mixtures. Under optimized conditions, calibration curves for mixtures of Cr2O3 and Cr(NO3)3·9H2O have slopes of 1.002, respective intercepts of −0.7% and 0.5%, and correlation coefficients of 0.9991. Fluorescence EXAFS from mixtures must be compared to fluorescence EXAFS from standards, and the matrices and thicknesses of standards and mixtures must be closely matched. Transmission EXAFS of standards must be obtained to correct for self-absorption effects.
Approach to Single Molecule Detection Using Surface-Enhanced Resonance Raman Scattering (SERRS): A Study Using Rhodamine 6G on Colloidal Silver
Authors: Kneipp Katrin , Wang Yang , Dasari Ramachandra R. , Feld Michael S.
Published: May 2005

We have measured surface-enhanced resonance Raman scattering (SERRS) spectra of rhodamine 6G (R6G) at concentrations as low as 8 × 10−16 M in colloidal silver solution activated by NaCl ions. The spectra were measured with a fiber-optic probe using the 514.5-nm argon-ion laser line as excitation source and a charge-coupled-device (CCD) detection system. The correlation of SERRS photo counts and R6G concentration was found to be linear between 8 × 10−11 and 8 × 10−14 M concentrations within our experimental accuracy. Experiments conducted with small scattering volumes show that fewer than 100 R6G molecules are sufficient to give rise to a SERRS spectrum with reasonable signal-to-noise ratio. These results demonstrate that in certain cases SERRS can achieve detection limits comparable to those for fluorescence spectroscopy, and at the same time provides higher structural specificity than fluorescence. The possibilities of using SERRS for single molecule detection are discussed.
Expectation Minimum (EM): A New Principle for the Solution of Ill-Posed Problems in Photothermal Science
Authors: Power J. F. , Prystay M. C.
Published: May 2005

The expectation-minimum (EM) principle is a new strategy for recovering robust solutions to the ill-posed inverse problems of photothermal science. The expectation-minimum principle uses the addition of well-characterized random noise to a model basis to be fitted to the experimental response by linear minimization or projection techniques. The addition of noise to the model basis improves the conditioning of the basis by many orders of magnitude. Multiple projections of the data onto the basis in the presence of noise are averaged, to give the solution vector as an expectation value which reliably estimates the global minimum solution for general cases, while the conventional approaches fail. This solution is very stable in the presence of random error on the data. The expectation-minimum principle has been demonstrated in conjunction with several projection algorithms. The nature of the solutions recovered by the expectation minimum principle is nearly independent of the minimization algorithms used and depends principally on the noise level set in the model basis.
Ultraviolet Resonance Raman Study of Nylon-6
Authors: Katagiri Gen , Leonard James D. , Gustafson Terry L.
Published: May 2005

Ultraviolet resonance Raman spectra of nylon-6 have been investigated with the use of a quasi-continuous UV excitation source based on cw mode-locked Nd:YAG and Nd:YLF lasers. The selective enhancement of the amide vibrational modes is discussed in relation to the reported results for simple amide compounds and polypeptides in aqueous solution. The ultraviolet excitation can extract the amide III mode at 1280 cm−1 for the first time, from significantly overlapped CH2 vibrational modes. The UV-enhanced mode is observed at 1380 cm−1 and is attributed to the controversial amide S mode. We also demonstrate the utility of the present quasi-continuous laser system as an excellent UV source for ultraviolet resonance Raman studies of solid materials.
Depth Profile Studies Using Laser-Induced Plasma Emission Spectrometry
Authors: Anderson David R. , McLeod Cameron W. , English Tim , Smith A. Trevor
Published: May 2005

The application of laser-induced plasma emission spectrometry to the depth profile measurement of coatings on steel is examined. The effects of key experimental parameters, such as laser energy and sample position relative to the laser focal point, on depth profile performance were characterized for a Zn/Ni coating on steel. With preferred operating conditions, linear calibrations against coating thickness for Zn/Ni (2.7 to 7.2 μm) and Sn (0.38 to 1.48 μm) on steel were achieved with good precision (3.5% relative standard deviation). An ultra-thin coating of Cr (20 nm) on steel was also detected by the technique. The depth profile performance and rapid measurement times, typically less than 60 s, indicate that the technique may be useful in industrial applications.
Long-Distance Detection of Laser-Produced Ions by a Reflectron Mass Spectrometer
Authors: Situ Wen , De Young Russell J.
Published: May 2005

Laser-produced ions were detected and analyzed remotely by a reflectron mass spectrometer for determination of the elemental composition. Detection of ions at 3.9 m from the target was accomplished. Elemental and isotopic mass spectra of aluminum, germanium, copper, silver, and complex targets such as a lunar simulant and Standard Reference Material 1834 were mass-analyzed at 1 × 109 W/cm2 (0.02 wt % detection limit), giving good correlation with manufacturers' stated elemental composition and yield. Mass spectra could be obtained in a single laser pulse. The mass resolution is 62 at mass 63 and 77 at mass 28. Such a system could be extended to a remote laser mass spectrometer on a lunar rover or satellite for planetary surface mass analysis.
Prediction of the Lowest-Energy Non-Koopmans Doublet States and the First Ionization Potentials of Polycyclic Aromatic Systems from Their Triplet-State Energies
Authors: Husain Mudassir M. , Khan Zahid H. , Haselbach Edwin
Published: May 2005

This paper presents some new relations connecting the triplet-state energy of an alternant aromatic hydrocarbon with that of its excited doublet state as well as its first ionization potential. The energy relation between the doublet and triplet states is basically a simplified version of the SDT relation but the predictive power of the proposed correlation is considerably better in spite of the drastic assumptions made in the model. Incorporation of molecular size in the doublet-triplet correlation has no appreciable effect on the predictions, but its inclusion in the ionization potential vs. triplet-state energy relation leads to a significant improvement in the results. It is explained on the basis of our new finding that the Coulomb term appearing in the expression for the ionization potential behaves in the same manner as the molecular size, which thus accounts for electron interaction in the model. The proposed correlations provide a simple but powerful means to estimate the first ionization potentials and excited doublet-state energies of polycyclic aromatic hydrocarbons directly from the knowledge of their triplet-state energies.
Simultaneous Determination of Arsenic(III) and Antimony(III) by Ozone-Induced Gas-Phase Chemiluminescence
Authors: Galbán Javier , Vela Jesus , Soria Maria T. Martínez , Aured Maria , Castillo Juan R.
Published: May 2005

A combined hydride-generation/gas-phase chemiluminescence (HG-GPCL) method for the determination of arsenic(III) and antimony(III) by using a conventional luminometer is proposed. The method was optimized in terms of the type of reaction chamber, the instrumental settings, and the hydride generation and reaction conditions used. It provides a linear response to As(III) and Sb(III) above a concentration of 0.05 and 0.50 mg L−1, respectively, with a relative standard deviation of ∼3% for both species. Arsenic and antimony can thus be determined simultaneously by (1) their differential effect on the signal obtained with an optical filter placed between the reaction chamber and detector, or (2) the difference between the peak height/peak area ratio of the transient signal for their hydrides. Both procedures were applied to the determination of arsenic and antimony in various synthetic aqueous samples with good accuracy and precision. The effect of potential interferences including anionic and hydride-forming inorganic species was investigated.
Spectroscopic Studies of New Blue Laser Dyes in Tetrahydrofuran Solution and in Composite Glass
Authors: Gvishi R. , He G. S. , Prasad P. N. , Narang U. , Li M. , Bright F. V. , Reinhardt B. A. , Bhatt J. C. , Dillard A. G.
Published: May 2005

We have investigated the linear absorption, emission wavelength-dependent excitation, fluorescence polarization excitation, and lasing properties of new UV-blue dyes. The dyes are didecyl para-polyphenyl heptamer (DDPPH), didecyloxy para-polyphenyl heptamer (DDOPPH), and bisbenzothiazole 3,4- didecyloxy thiophene (BBTDOT). We studied the effect of dye concentration on absorption and emission and the origin of the peaks in tetrahydrofuran solution and in a composite glass. We show that, in a composite glass, it is possible to impregnate the dye with density of several orders without aggregation effects. The two heptamer dyes were found to be very photostable. All three dyes are promising candidates as laser dyes in the UV. Under excitation with a frequency-doubled dye laser (300 nm), the DDPPH lased at 377 nm. The DDOPPH lased at 425 nm and the BBTDOT lased at ∼450 nm when excited by the third harmonic of a Nd:YAG laser (355 nm). The output from the second heptamer in tetrahydrofuran was photostable (less than 10% decrease) for more than 900,000 pulses and with a slope efficiency of approximately 20%.
Fluorescence Studies of Complex Coal Liquid Samples Using the Lifetime Synchronous Spectrum (LiSS)
Authors: Shaver Jeremy M. , McGown Linda B.
Published: May 2005

An analysis of coal liquids is demonstrated in the first application of the lifetime synchronous spectrum (LiSS) to the characterization of complex samples. The measurement of wavelength-resolved fluorescence lifetimes in the LiSS is shown to enhance the fingerprinting of coal liquids relative to conventional synchronous luminescence spectroscopy. The concentration independence of fluorescence lifetimes of individual compounds provides unique information about the composition of the coal liquids and the sources of their spectral features, indicating similarities among different samples and leading to the identification of regions in the synchronous spectra that are best for discriminating among the samples. The LiSSes also provided information about the nature of the processes responsible for spectral red shifts that occurred with increasing concentration of coal liquid.