bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of Methamphetamine and its Related Compounds Using Fourier Transform Raman Spectroscopy
Authors: Tsuchihashi Hitoshi , Katagi Munehiro , Nishikawa Mayumi , Tatsuno Michiaki , Nishioka Hiroshi , Nara Akishi , Nishio Etsuo , Petty Chris
Published: October 2003

Fourier transform Raman spectroscopy (FT-Raman) is investigated as a simple and rapid method for the determination of the abused drug methamphetamine and its related compounds. Compounds can be reliably identified by using measurements made nondestructively and without the need for any sample preparation in around 1 min. The Raman spectrum of methamphetamine hydrochloride (MA) shows clear differences in spectra from a range of its related compounds such as amphetamine sulfate and ephedrine hydrochloride. These differences are adequate for spectral differentiation of the compounds. With the use of the FT-Raman technique, MA is also reliably identifiable to a detection limit of 1% (w/w) diluted in sodium chloride or water. FT-Raman spectra of MA were recorded through plastic packaging (polyethylene or polypropylene bags) typical of that used either by criminals for transportation or by law enforcement for containing and sealing evidence. Measurements could be made directly without removing the drug from the bag; excellent-quality spectra could be obtained with very little perturbation by the plastic bag.
Effect of Oxygen Ashing on Analyte Transport Efficiency Using ETV-ICP-MS
Authors: Fonseca R. W. , Miller-Ihli N. J. , Sparks C. , Holcombe J. A. , Shaver B.
Published: October 2003

Oxygen ashing has been used in electrothermal atomic absorption spectroscopy to eliminate organic matrix sample components and is particularly useful when doing direct solids analysis of biologicals using ultrasonic slurry sampling. Oxygen ashing has also proven to be useful for the analysis of slurry samples using ultrasonic slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry (USS-ETV-ICP-MS). In this work, the effect of oxygen ashing on analyte transport in USS-ETV-ICP-MS was evaluated. Oxygen ashing in the presence of Pd modifier (Pd/O2) enhances analyte transport efficiency, possibly as a result of an increase in the number of carbon particles present in the graphite furnace during the vaporization step. These carbon particles act as a physical carrier, providing a surface on which the analytes can condense to be transported more efficiently. The carbon produced at earlier times, with Pd/O2, may be the result of either dissociation or fracture of the graphite during the rapid heating of the furnace. Pd, which was initially added to act as a physical carrier, also seems to be acting as a catalyst for carbon oxidation. The shift in the carbon signal toward earlier times when using oxygen ashing was observed only when Pd was present. In addition, scanning electron micrographs of a home-made graphite platform revealed that portions of the graphite substrate were missing when Pd/O2 was used and that clearly visible pits were found in the graphite. Oxygen ashing combined with 1 μg Pd improves quantitative results by removing the organic part of the matrix present in slurry samples while enhancing analyte transport efficiency by providing carbon particles that serve as a physical carrier.
XPS Study of a New Heterogeneous Ruthenium Catalyst Precursor
Authors: Smet P. , Verpoort F. , De Doncker G. , Bossuyt A. R. , Fiermans L. , Verdonck L.
Published: October 2003

The catalyst precursor has been synthesized by modifying the silica surface with ClPPh2 followed by a surface reaction with RuCl3. Supports consisting of a thin layer of SiO2 on a silicon single crystal have been used. Characterization of the different stages in the reaction procedure has been performed by a combination of conventional and angle-resolved X-ray photoelectron spectroscopy (XPS) using RuCl3/P(C6H5)2/SiO2/Si(100) model precursors. Different types of ruthenium centra have been identified.
Investigation of Chemical Interactions at the Steel/Polymer Interface by FT-IR Diffuse Reflectance Spectroscopy
Authors: Bistac S. , Vallat M. F. , Schultz J.
Published: October 2003

Interactions between a steel surface and an ethylene–vinyl acetate copolymer grafted with maleic anhydride have been investigated by Fourier transform infrared (FT-IR) diffuse reflectance spectroscopy. The failed surfaces obtained after a mechanical separation of the polymer/steel assemblies have been analyzed. The results show that a new peak appears, characteristic of a carboxylate group. A model system composed of maleic anhydride deposited on iron plates has been studied in order to consider more specifically the reactivity of maleic anhydride. Peaks characteristic of metallic carboxylate complexes are present in the spectrum. A two-step mechanism has been proposed: the opening of the anhydride cycle by a hydrolysis reaction, leading to the formation of a carboxylic diacid, followed by the reaction of the acid with some oxidized metallic elements present at the metal surface. This study underlines the contribution of FT-IR reflectance techniques to the understanding of the adhesion mechanisms.
Noninvasive Assessment of Regional and Temporal Variations in Tissue Oxygenation by Near-Infrared Spectroscopy and Imaging
Authors: Sowa Michael G. , Mansfield James R. , Scarth Gordon B. , Mantsch Henry H.
Published: October 2003

A combination of near-infrared spectroscopy and discrete wavelength near-infrared imaging is used to noninvasively monitor the forearm during periods of restricted blood outflow (venous outflow restriction) and interrupted blood inflow (ischemia). Multivariate analysis of image and spectral data time courses was used to identify highly correlated spectral and regional domains, while fuzzy C-means clustering of image time courses was used to reveal finer regional heterogeneities in the response of stressed tissues. Localized near-infrared spectroscopy was used to investigate the magnitude of the bulk changes in the tissue optical properties and the variation in tissue oxygenation saturation during venous outflow restriction and complete forearm ischemia. The imaging and spectroscopic analyses revealed highly localized regional variations in tissue oxygen saturation during forearm ischemia as compared to the more diffuse and global response of the forearm during venous outflow restriction.
Titanium: Sapphire Laser as an Excitation Source in Two-Photon Spectroscopy
Authors: Fisher W. G. , Wachter E. A. , Armas Michael , Seaton Colin
Published: October 2003

The passively mode-locked titanium: sapphire laser provides new opportunities for acquiring two-photon spectral data in the near-infrared, a region not commonly accessible to synchronously pumped dye lasers. This source generates pulses with peak powers near 100 kW at average powers over 1 W and is capable of yielding two-photon signals roughly two orders of magnitude larger than is possible with synchronously pumped dye lasers. However, the multimode output of this laser exhibits significant temporal and spectral pulse profile variations as the laser wavelength is tuned. As a consequence, peak powers of the titanium:sapphire laser can vary independently from average power across the tuning range. This wavelength dependence, coupled with the quadratic dependence of the two-photon signal upon the instantaneous power of the laser, precludes simple average power correction of nonlinear spectral band shapes. Here, we investigate the key properties of the titanium:sapphire laser as an excitation source for two-photon spectroscopy. We also identify a chemical reference suitable for obtaining source-corrected excitation spectra in the near-infrared using a double-beam, ratiometric approach; this is based on a source-in-dependent two-photon excitation spectrum for the laser dye coumarin-480 that has been obtained with a single-frequency titanium:sapphire laser. From these data, correction factors are generated for correction of multimode source data.
Precise Determination of Percent Cure of Epoxide Polymers and Composites via Fiber-Optic Raman Spectroscopy and Multivariate Analysis
Authors: Aust Jeffrey F. , Booksh Karl S. , Stellman Christopher M. , Parnas Richard S. , Myrick Michael L.
Published: October 2003

A method for real-time determination of the percent cure of epoxies via in situ fiber-optic Raman spectroscopy has been developed. This method utilizes a probe design developed for real-time monitoring of polymer curing and multivariate analysis to interpret the data and determine percent cure. This method was demonstrated to be reliable to ±0.54% of cure in laboratory samples over a 50–99% cure range. A preliminary study measuring cure percentage in an industrial, glass-reinforced composite has been shown to be reliable to ±0.82% in the 40–90% cure range.
Spectroscopic Studies of the Interaction of 1,4-Diphenyl-1,3-Butadiene with α-, β-, and γ-Cyclodextrins
Authors: de la Peña Arsenio Muñoz , Agbaria Rezik A. , Peña Montserrat Sánchez , Warner Isiah M.
Published: October 2003

Steady-state fluorescence, anisotropy, and UV-visible absorption measurements have been used to investigate the structure and spectroscopic characteristics of the complexes formed by trans, trans-1,4-diphenyl-1,3-butadiene (DPB) with α-, β-, and γ-cyclodextrins (CDs). The behavior of α-CD with DPB is very different from that of DPB with respect to β-CD or γ-CD. In the presence of α-CD, clear solutions with high absorption and fluorescence emission, relatively high anisotropy, a rapid equilibrium reaction, and Benesi–Hildebrand plots lead us to conclude that normal 2:1 inclusion compounds are formed. In the presence of γ-CD, turbid solutions, with absorption and fluorescence emission intensities lower than those in α-CD, higher values of anisotropy, slow equilibrium reaction, and spectral shifts to the red in the absorption, excitation, and emission wavelengths are evidence of the formation of extended linear aggregates. In the presence of β-CD, both mechanisms of inclusion appear to be present.
Infrared Spectroscopy in Aqueous Solution: Difficulties and Accuracy of Water Subtraction
Authors: Rahmelow Kim , Hübner Wigand
Published: October 2003

The long-term reproducibility of a set of water spectra in the infrared region with cell thicknesses of less than 10 μm was tested. With the application of a computer routine for subtraction in the range from 2600 to 1100 cm−1 and the use of additional phase and nonlinearity corrections, an accuracy better than one milliabsor-bance unit (mAU) can be achieved, if the temperature is kept constant within a tenth of a degree or if a temperature correction factor is implemented in the subtraction routine. The subtraction of water from an aqueous protein solution reduces the spectral range for a correction to 2300–1800 cm−1. In this region the protein absorption, as derived from dry protein films, is constant, and because of the association band at 2125 cm−1 water exhibits good subtraction properties. However, the reduction of the spectral range for the water subtraction leads to an increase in the residual error to 12 mAU at 1650 cm−1. This standard deviation can be reduced to 6–7 mAU by applying a second subtraction range from 4000 to 3650 cm−1. A further reduction of this error to 3–5 mAU is obtained by implementing a constant ratio of the integrated intensities of the amide I and amide II bands in the procedure of subtracting water from aqueous protein solutions. The remaining inaccuracy is mainly caused by uncompensated phase error.
Spectral Line Narrowing by Use of the Theoretical Impulse Response
Authors: Saarinen Pekka E.
Published: October 2003

Fourier transform spectroscopy is nowadays able to produce spectra with extremely high signal-to-noise ratios, and thus extremely high information content. Unfortunately, this information is partially lost because of a lack of sufficiently effective line-narrowing methods to resolve overlapping spectral lines. A novel, and very promising, approach to the problem is the LOMEP line-narrowing method, based on consecutive linear prediction; the line narrowing is carried out in the signal domain by extrapolating the Fourier transform of the spectrum. However, LOMEP is not yet optimal. For example, it does not make use of the information contained in the output line shapes to correct the errors made in linear prediction. In fact, that procedure would not even be possible by using the prediction strategy adopted by LOMEP. Therefore it is possible to considerably improve the method by including the information contained in the distortions of the output spectral lines. In this paper a new method of line narrowing is presented, based on progressive improvement of the prediction until the output is free from distortions. The method is very easy to use and does not require a profound understanding of the underlying mathematics.
External Reflection Infrared Spectroscopy of Anisotropic Adsorbate Layers on Dielectric Substrates
Authors: Brunner Helmut , Mayer Ulrich , Hoffmann Helmuth
Published: October 2003

Monolayers of octadecylsiloxane were formed on native silicon (Si/SiO2) and glass surfaces by adsorption from dilute solutions of octadecyltrichlor osilane and were investigated by polarization- and angle-dependent external reflection infrared spectroscopy. In contrast to metal substrates, both the parallel and perpendicular vibrational components of the adsorbate can be detected on these dielectric surfaces. The monolayer reflection spectra show significant changes as a function of the light incidence angle and the polarization of the infrared radiation, which contain detailed information on the surface orientation of the film molecules. Spectral simulations based on classical electromagnetic theory yield an average 10° tilt angle of the hydrocarbon chains with respect to the surface normal on both silicon and glass surfaces. Despite this apparent structural identity of the monolayer films on silicon and glass, significant differences are observed in the monolayer reflection spectra resulting from purely optical effects of the substrate.
Infrared Spectra and Elemental Composition in Recent Carbonate Skeletons: Relationships between the ν2 Band Wavenumber and Sr and Mg Concentrations
Authors: Dauphin Y.
Published: October 2003

Biological aragonites show various chemical compositions (Sr and Mg) related to the systematic position of the organisms. It is well known that Cnidaria tests have high Mg and Sr aragonites, whereas Mollusca shells have low Mg and Sr aragonites. Sponges have low Mg and high Sr aragonites. The linear correlation between Mg and Sr concentrations is positive. DRIFT spectra show that the wavenumber of a part of the doublet ν2 significantly differs in the Mollusca shells and the Sponges and Cnidaria set: 863.7 cm−1 in Mollusca, 858.8 cm−1 in Sponges + Cnidaria. The other part of the doublet is similar in the two sets (844.1 cm−1). ν1 and the doublet ν4 do not seem to be altered. There is a strong linear correlation between the ν2 wavenumber and the Mg and Sr concentrations in these biological aragonites. It is known that the calcite–aragonite transition apparently shifts the wavenumber of ν2, but such a shift has not been observed in one mineral.
Optimized External IR Reflection Spectroscopy for Quantitative Determination of Borophosphosilicate Glass Parameters
Authors: Zhang Lizhong , Franke James E. , Niemczyk Thomas M. , Haaland David M.
Published: October 2003

Infrared (IR) external reflection spectroscopy has been optimized for the quantitative determination of composition and film thickness of borophosphosilicate glass (BPSG) deposited on silicon wafer substrates. The precision of the partial least-squares calibrations for boron and phosphorus contents and thin-film thickness were measured as the cross-validated standard error of prediction statistic. The results showed that BPSG IR reflection spectra collected over a wide range of incident IR radiation angles (15°, 25°, 45°, and 60°) can be used for the simultaneous quantification of these three BPSG parameters. When high angles of incidence were employed, the measurement was found to be more sensitive to small errors in the angle of incidence. The polarization state of the incident IR radiation did not noticeably affect the prediction of the three calibrated BPSG parameters. The results achieved in this study provide guidelines for at-line process monitoring and quality control of BPSG thin films used in the fabrication of microelectronic devices. Index Headings: IR reflection; Multivariate calibration; Partial least-squares
In Situ Diffusion and Miscibility Studies of Thermoplastic PDLC Systems by FT-IR Microspectroscopy
Authors: Challa Sudarsana R. , Wang Shi-Qing , Koenig Jack L.
Published: October 2003

Infrared microspectroscopy was used to study the interaction of liquid crystal (E7) with poly( n-butyl methacrylate) (PBMA). A novel experimental technique is introduced to conduct in situ diffusion and miscibility studies of polymer-dispersed liquid crystal (PDLC) systems. The amount of liquid crystal dissolved in the polymer matrix is determined by using the IR microspectroscope, which is a powerful tool for characterizing domains on the order of tens of micrometers. Quantitative phase diagrams are constructed for the PBMA and E7 mixture. It is observed that the diffusion of E7 into PBMA follows Fick's second law of diffusion with a diffusion coefficient of (1.3 ± 0.2) × 10−7 cm2/s at 61 °C. The intensities of the peaks in the IR spectrum were used as a measure of the concentration of the components. The combination of IR microspectroscopy with the contact method is proven to be a powerful technique for the quantitative elucidation of phase diagrams.
Comparison of Multivariate Calibration and Discriminant Analysis in Evaluating NIR Spectroscopy for Determination of Meat Tenderness
Authors: Næs Tormod , Hildrum Kjell Ivar
Published: October 2003

Often the primary goal of analytical measurement tasks is not to find good estimates of continuous reference values but rather to determine whether a sample belongs to one of a number of categories or subgroups. In this paper the potential of different statistical techniques in the classification of raw beef samples in tenderness subgroups was studied. The reference values were based on sensory analysis of beef tenderness of 90 samples from bovine M. longissimus dorsi muscles. The sample set was divided into three categories—very tough, intermediate, and very tender—according to degree of tenderness. A training set of samples was used to find the relationship between category and near-infrared (NIR) spectroscopic measurements. The study indicates that classical discriminant analysis has advantages in comparison to multivariate calibration methods [i.e., principal component regression (PCR)], in this application. One reason for this observation seems to be that PCR underestimates high measurement values and overestimates low values. In this way most samples are assigned to the intermediate group of samples, causing a small number of erroneous classifications for the intermediate subgroup, but a large number of errors for the two extreme groups. With the use of PCR the number of correct classifications in the extreme subgroups was as low as 23%, while the use of discriminate analysis increased this number to almost 60%. The number of classifications in correct or neighbor subgroup for the two extreme subgroups was equal to 97%. A “bias-correction” was also attempted for PCR, and this gave results comparable to the best results obtained by discriminant analysis methods. Test sets used NIR analysis of fresh, raw beef samples with different processing. While this spectroscopic approach had previously been shown to be useful with frozen products, it appears unsuitable at this time for fresh beef. However, its marginal analytical utility proved useful in evaluating the two classification approaches employed in this study.
New High-Pressure Fiber-Optic Cell for Time-Resolved Emission and Absorbance Measurements in Near- and Supercritical Solvents
Authors: Rhodes Timothy A. , Fox Marye Anne
Published: October 2003

A new fiber-optic high-pressure cell for time-resolved absorbance and fluorescence measurements in near- and supercritical solvents is presented. It consists entirely of commercial components, thus facilitating ease of construction and maintenance and facilitating component exchange to incorporate materials that can withstand a broad range of pressures and temperatures. The adaptability of the cell and the applicability of the pressure-sealing technique to a variety of emission and fast kinetic measurements are discussed.
On-Line Post Consumer Package Identification by NIR Spectroscopy Combined with a FuzzyARTMAP Classifier in an Industrial Environment
Authors: Feldhoff R. , Wienke D. , Cammann K. , Fuchs H.
Published: October 2003

An optical setup consisting of a high-throughput near-IR (NIR) spectrograph with an InGaAs-array detector and specially designed collection optics is used to record spectra from post consumer packages located on an industrial conveyor belt. NIR spectra of packages of different polymers (PE, PET, PP, PS, and PVC) and of a cardboard/plastic compound are recorded between 900 and 1700 nm with 6.3-ms integration time. The visual distinction between the spectra is demonstrated by aid of principal component analysis (PCA) plots. The spectra are further classified by a FuzzyARTMAP neural network. The method is assessed to be suitable for on-line identification under industrial conditions.
Simultaneous Determination of Sugars by Multivariate Analysis Applied to Mid-Infrared Spectra of Biological Samples
Authors: Cadet Frédéric , Robert Christine , Offmann Bernard
Published: October 2003

We have investigated the use of principal component analysis (PCA) to describe and assess mid-infrared spectral data obtained from complex biological samples containing sucrose, fructose, and glucose. The correlation coefficients between spectral data and chemical values of each variable (sucrose, glucose, fructose, total sugars, and reducing sugars) showed that in each case, axes 1, 3, 4, and 5 had the highest values. These values also indicated which axes each variable was mostly correlated with. The results also showed that the samples were distributed according to their sucrose concentrations (or total sugars) along a concentration gradient in the projection plan formed between axes 1 and 3. No clear discrimination according to concentration was observed with other factorial maps. Prediction equations that linked sucrose, fructose, glucose, total sugar, and reducing sugars concentrations to the spectral data were established by regression on the principal component. Very high correlation coefficients values between the first 10 axes and the chemical values were obtained (between 0.9757 and 0.998). From such aqueous biological samples containing a ternary mixture of sucrose, fructose, and glucose, it was possible to (1) identify the characteristic IR bands of these different sugars (and their combination: reducing sugars/total sugars) and (2) to specifically measure their concentrations with a relatively good accuracy.
Rejection of Background Light Using Single-Wavelength Detection in Nonlinear Raman Spectroscopy
Authors: Chen Peter C.
Published: October 2003

A new method for single-wavelength detection (SWD) spectroscopy has been developed with the use of synchronous scanning of an optical parametric oscillator (OPO). With the combination of SWD with spatial and temporal discrimination, a high level of background light rejection is achieved. Results show sufficient ambient room light rejection for obtaining complete gas-phase nonlinear Raman spectra with no detectable signs of interference.
Fluorescence Quenching of Polycyclic Aromatic Hydrocarbons by Cetylpyridinium Bromide: Discrimination between Alternant and Nonalternant Hydrocarbons
Authors: Ayala Juan H. , Afonso Ana M. , González Venerando
Published: October 2003

Molecules of polycyclic hydrocarbons (PAHs) that contain between two and five rings undergo quenching processes in the presence of cetylpyridinium bromide (CPB), which can act as quencher and as surfactant. The CPB concentration and the nature of the PAHs notably influence the inhibition mechanisms of fluorescence. Dynamic quenching is predominant for all hydrocarbons in solutions in which CPB is found in the form of monomers. When the quencher forms premicellar aggregates, fluoranthene, benzo[ a]pyrene, and benz[ a]anthracene undergo dynamic quenching, while for the remaining PAHs the dynamic and static processes coexist. In micellar CPB solutions the static quenching mechanism is predominant. The correlations existing between the quenching constant in the premicellar zone and topological and geometrical descriptors of the PAHs show the different behavior of alternant and nonalternant hydrocarbons.
Discrimination of Reactive Dyes on Cotton Fabric by Raman Spectroscopy and Chemometrics
Authors: Kokot S. , Tuan Nguyen Anh , Rintoul L.
Published: October 2003

FT-Raman spectra were obtained from undyed poplin cotton fabric and from the same fabric differently dyed with a bi-functional reactive dye, Cibacron C (molecular structure unknown); the four series of the dyed samples each contained the dye in a different form—unfixed, ammonia-treated/unfixed, fixed, and ammonia-treated/fixed. The spectra were dominated by the dye, but the different states of the dye were not obviously differentiated. Application of principal component analysis showed that the spectral groups of the four different dye states can be discriminated from each other and from that of the undyed cotton. Further, for each series of the dyed fabrics, which contain samples with different amounts of dye, the individual dye concentration subgroups are distinguished. Exploratory quantitative studies suggested that FT-Raman spectroscopy may be a suitable quantitative method for the prediction of % concentration of the unfixed dye on cotton fabrics. A comparison of the FT-Raman results with those from a parallel FT-IR study reported elsewhere indicated that similar qualitative conclusions may be reached with both techniques. However, the FT-Raman approach does provide additional information from the dominating dye spectrum. A comparison of prediction of % concentration of the unfixed dye on the fabric indicated that better partial least-squares (PLS) calibration models may be obtained from the FT-Raman data, but the validation results from a small set of samples suggested only a marginal advantage with the use of the Raman approach.
Self-Modeling Mixture Analysis Applied to FT-Raman Spectral Data of Hydrogen Peroxide Activation by Nitriles
Authors: Vacque V. , Dupuy N. , Sombret B. , Huvenne J. P. , Legrand P.
Published: October 2003

In the analytical environment, spectral data resulting from analysis of samples often represent mixtures of several components. Extraction of information about pure components of these kinds of mixtures is a major problem, especially when reference spectra are not available or when unstable intermediates are formed. Self-modeling multivariate mixture analysis has been developed for this type of problem. In this paper two examples will be used to show the potential of this technique coupled with FT-Raman spectroscopy to elucidate reaction mechanisms and to follow in situ the kinetics of chemical transformations.
Laser-Induced Shock Wave Plasma Using Long-Pulse YAG Laser
Authors: Kurniawan Hendrik , Kagawa Kiichiro
Published: October 2003

A laser-induced shock wave plasma was generated by bombarding a brass target with a long-pulse YAG laser at reduced pressure. The characteristics of the laser plasma were studied by examining the reflection and diffraction of the laser plasma when an aluminum wedge block was placed in front of the plasma. A dramatic increase in the emission of the secondary plasma was observed, supporting the shock wave model. The collected data also confirm that the displacement length of the secondary plasma emission front is proportional time raised to the 0.6 power. The temperature of the secondary plasma was found to be 10,000 K at 5 mm above the target, decreasing to 6800 K at 10 mm above the target.
In Situ Temperature-Programmed Diffuse Reflectance Infrared Fourier Transform Spectroscopy (TPDRIFTS) of V2O5/TiO2 Catalysts
Authors: Centeno M. A. , Benítez J. J. , Malet P. , Carrizosa I. , Odriozola J. A.
Published: October 2003

Temperature-programmed diffuse reflectance infrared Fourier transform spectroscopy (TPDRIFTS) is proposed to follow in situ temperature-programmed reduction (TPR) and temperature-programmed desorption (TPD) experiments of catalytic systems, as a method for observing relationships between the surface structure and the reducibility of the catalyst under the actual reaction conditions. TPDRIFTS studies of desorption and reduction of a conventional V2O5/TiO2 catalyst have been carried out, showing the presence in both processes of four stages. Both desorption and reduction experiments result in similar DRIFTS spectra for temperatures below 400 °C, accounting for two processes: (1) water desorption and (2) condensation of highly dispersed vanadium species in between V2O5 islands on the anatase surface. V2O5 reduction by H2 takes place between 400 and 680 °C, being characterized by elimination of the first-overtone bands of V= O groups. DRIFTS is shown to be a very powerful tool to characterize both hydrogen-consuming and nonconsuming processes such as O= migration above 725 °C (stage IV). Relationships between the area of V = O overtones bands obtained by TPDRIFTS and the oxidation state of vanadium are proposed as a method to estimate this parameter under actual reaction conditions.
Infrared Reflectivity Determination of Alloy Composition in AlxGa1–xAs and InxGa1–xAs Structures
Authors: Engelbrecht J. A. A. , Botha J. R.
Published: October 2003

Fourier transform infrared reflectance spectroscopy can be used to establish the height of the transverse optic mode peak of AlAs at 361 cm−1. The peak height is found to be linearly dependent on the aluminum content in Al xGa1– xAs layers on GaAs substrates. Previously published spectra for In xGa1– xAs yielded a similar result for the In content, from the transverse optic mode peak of InAs at 220 cm−1. A quick and nondestructive technique is proposed for the determination of the aluminum and indium mole fraction in these structures.
1H NMR Study of the Reaction of Diacetylmelamine with Oxiranes
Authors: Lubczak Jacek
Published: October 2003

The reaction of 1 mole of melamine with 2 moles of acetic anhydride leads to diacetylmelamine (DAM), which is a mixture of two constitutional isomers: 90% N, N′-DAM and 10% N,N-DAM The reaction of 1 mole of DAM with 1–8 moles of oxiranes (ethylene and propylene oxides) was studied by 1H NMR spectroscopy. At the molar ratio of substrates 1: ∼ 2, no N,N′-diacetyl- N,N′-bis(2-hydroxyalkyl)melamine was formed, but the product of its intramolecular rearrangement, N,N′-bis(2-acetyloxyalkyl)melamine, was found. The latter reacted with the excess of oxiranes to appropriate tetrafunctional polyetherols containing s-triazine rings.
Quantitative Determination of the Scattering and Absorption Coefficients from Diffuse Reflectance and Transmittance Measurements: Application to Pharmaceutical Powders
Authors: Burger T. , Kuhn J. , Caps R. , Fricke J.
Published: October 2003

A measurement and data evaluation technique for the separate determination of the scattering and absorption properties of loose pharmaceutical powders is described. The equation of radiative transfer for diffuse reflectance and transmittance is analytically solved by using a three-flux approximation. Combined transmittance and reflectance measurements then allow one to derive both the scattering and the absorption coefficients. The scattering and absorption coefficients provide more information about particle size, degree of agglomeration, and chemical composition of the samples in comparison to the usual determination of only the ratio of the coefficients from diffuse reflectance measurements on optically thick samples. Furthermore, the theory of diffuse reflectance of optically thick samples according to Kubelka and Munk is compared to the three-flux approximation. The influence of the particle size on the scattering and absorption coefficient is investigated, and it is shown that the assumption of a wavelength-independent scattering coefficient, though often made in reflectance spectroscopy, is not generally valid.
Approach to Determine Electrochemical Interface Structure from Surface Optical Spectroscopy
Authors: Georgiadis R. , Lambrakos S. G. , Trzaskoma-Paulette P. P.
Published: October 2003

We present a general approach for establishing correlations between the optical second-harmonic (SH) response generated from a metal/electrolyte interface and the interface structure. Our approach entails the construction of a response function for optical second-harmonic generation (SHG) from the metal surface in the presence of an electrolyte and an applied electrochemical field. The response function approach, a powerful and general method, is developed here for the first time for SHG data. Here, the response function describes the nonlinear optical response of a mesoscopic region of the surface to an applied static mesoscopic electric field and is a characterization of how the electrostatic nature of the surface responds to changes in the concentration and composition of the electrolyte. We construct the response function from experimental measurements of the SH response and from models representing known interface structure. A significant aspect of our approach is that it combines, through the modification of the response function, existing models of metal-interface structure with models for mechanisms of SHG response. Our approach provides, therefore, a framework for correlating existing and emerging models of the double layer with optical experimental measurements. Case study analyses of prototype interface systems are presented here, demonstrating applications of our approach.
Selection of Internal Standards for the Determination of Major and Minor Elements in Silicate Rocks and Limestones by Laser Ablation Inductively Coupled Plasma Atomic Emission Spectrometry
Authors: Kanicky Viktor , Mermet Jean-Michel
Published: October 2003

Use of contained and added internal standards has been compared in laser ablation ICP-AES of silicate rocks and limestones to improve both precision and accuracy. Glass disks obtained by fusion of rocks with lithium tetraborate were sampled by means of a Q-switched Nd:YAG laser (355 nm, 10 Hz, 10 mJ per shot) and analyzed with an ICP emission spectrometer equipped with a segmented charge-coupled device detector. The Si and Ca major elements of the silicate and limestone samples, respectively, were compared with the Li and B flux elements for internal standardization. A 2- to 5-times improvement in the percent relative standard deviation (%RSD) of the repeatability was found, irrespective of the internal standard, leading to a repeatability in the 1–2% RSD range. On the basis of the use of Li and B as internal standards, linear calibration graphs were obtained for Si, Al, Ca, Mg, Fe, Ti, Na, and K by using reference geological materials. The possibility of using flux elements overcomes the need to have prior knowledge of the concentration when a contained element is being used as an internal standard.
FT-IR Study of Water Desorption from Collagen Films
Authors: Shibata Tomoko , Tonan Kenji , Yasuda Toshio , Ikawa Shun-Ichi
Published: October 2003

FT-IR spectra of collagen films set in a vacuum chamber have been measured as a function of time for evacuation at 35 and 75 °C. From the difference in the spectra before and after evacuation, three distinct peaks were found at 3080, 3240, and 3480 cm−1. The latter two peaks have been assigned to two types of water molecules bound in the collagen films from comparison with frequencies of solid and liquid water. The intensity change of these peaks with the evacuation time, therefore, indicates progress of the desorption of water from the collagen film. The first peak, its frequency being too low to be assigned to water, may be assigned to some functional groups of collagen which bind tightly to the water molecules. This suggestion is supported by the fact that the rate of intensity change during evacuation is approximately the same for the 3080- and 3240-cm−1 peaks. On the other hand, the intensity of the 3480-cm−1 peak changes faster, which means that the water molecules assigned to this peak are more loosely bound in the collagen film than are those assigned to the 3240-cm−1 peak. It has been found that the rate coefficients of water desorption decrease with the evacuation time. This result is probably due to the effect of the diffusion of water through the collagen film.
Multivariate Classification of the Infrared Spectra of Cell and Tissue Samples
Authors: Haaland David M. , Jones Howland D. T. , Thomas Edward V.
Published: October 2003

Infrared microspectroscopy of biopsied canine lymph cells and tissue was performed to investigate the possibility of using IR spectra coupled with multivariate classification methods to classify the samples as normal, hyperplastic, or neoplastic (malignant). IR spectra were obtained in transmission mode through BaF2 windows and in reflection mode from samples prepared on gold-coated microscope slides. Cytology and histopathology samples were prepared by a variety of methods to identify the optimal methods of sample preparation. Cytospinning procedures that yielded a monolayer of cells on the BaF2 windows produced a limited set of IR transmission spectra. These transmission spectra were converted to absorbance and formed the basis for a classification rule that yielded 100% correct classification in a cross-validated context. Classifications of normal, hyperplastic, and neoplastic cell sample spectra were achieved by using both partial least-squares (PLS) and principal component regression (PCR) classification methods. Linear discriminant analysis applied to principal components obtained from the spectral data yielded a small number of misclassifications. PLS weight loading vectors yield valuable qualitative insight into the molecular changes that are responsible for the success of the infrared classification. These successful classification results show promise for assisting pathologists in the diagnosis of cell types and offer future potential for in vivo IR detection of some types of cancer.
Amplitude Spectrum Approach in Dynamic FT-IR Spectroscopy of Uniaxially Oriented Poly(Ethylene Terephthalate) Films. Part I: Draw Ratio Dependence
Authors: Sonoyama Masashi , Shoda Kunihiro , Katagiri Gen , Ishida Hideyuki
Published: October 2003

A method of data manipulation using the dynamic magnitude spectrum and the static absorbance spectrum is applied to uniaxially drawn poly(ethylene terephthalate) films with five different draw ratios for the evaluation of the amplitude of dynamic structural changes under a sinusoidal strain at the level of a functional group. This analysis revealed that, in the drawn film, the skeletal structures, such as the C–O bond in the ethylene glycol unit and the phenyl ring, are susceptible to deformation by mechanical stretching, while the dynamic structural changes around the methylene group are small. It was assumed that the backbone of the polymer is responsible for the change of the mechanical properties induced by the drawing of the film.
Digital Signal Processing for Step-Scan Fourier Transform Infrared Photoacoustic Spectroscopy
Authors: Drapcho David L. , Curbelo Raul , Jiang Eric Y. , Crocombe Richard A. , McCarthy William J.
Published: October 2003

A software-based digital signal processing (DSP) method using the data system processor has been developed to demodulate the photoacoustic responses of a sample to the fundamental phase modulation frequency and its harmonic frequencies (up to the ninth harmonic) in step-scan FT-IR photoacoustic measurements, without the use of any additional hardware. The DSP algorithm and its sampling depth multiplexing advantages are compared to conventional hardware demodulation. Comparison of results from the DSP method to those from hardware demodulators are shown at both the phase modulation frequency and the harmonics, and application of the DSP method to step-scan photoacoustic measurements with phase modulation is discussed as it applies to obtaining depth profile information in heterogeneous materials.
Step-Scan Fourier Transform Vibrational Circular Dichroism Measurements in the Vibrational Region above 2000 cm−1
Authors: Long Fujin , Freedman Teresa B. , Tague Thomas J. , Nafie Laurence A.
Published: October 2003

We present the results of a new Fourier transform infrared vibrational circular dichroism (FT-IR-VCD) spectrometer optimized for performance in the near-infrared region above 2000 cm−1. The instrument is capable of operating in either the conventional rapidscan mode or the step-scan mode and is designed around the Bruker IFS 55 FT-IR spectrometer. We find that in the region of hydrogen stretching, the instrument performs as well as or better than (depending on the spectral coverage and resolution desired) a corresponding dispersive grating VCD spectrometer, with noise levels at approximately 10−6 Δ A units for a two-hour collection at 8-cm−1 resolution. The performance is approximately a factor-of-2 better in signal-to-noise ratio in optimized step-scan operation in comparison to the corresponding results in rapid-scan operation. The reasons are traced to advantages in electronic filtering and undersampling efficiency in step-scan mode. It is expected that the advantages of step-scan will increase with increasing optical transition frequency, such as the region of overtone and combination bands between 4000 and 8000 cm−1.
In situ and Real-Time Surface-Enhanced Infrared Study of Electrochemical Reactions
Authors: Osawa Masatoshi , Yoshii Katsumasa
Published: October 2003

Surface-enhanced infrared absorption spectroscopy (SEIRAS) in conjunction with cyclic voltammetry has been applied to in situ and real-time monitoring of the electrochemical redox reactions of heptylviologen at a silver electrode surface. The high sensitivity of SEIRAS enables the real-time spectral monitoring of the irreversible reaction processes on the millisecond time scale with rapid-scan interferometry. With the combination of the molecular information obtained from the spectra and the kinetic data obtained by cyclic voltammetry, the complex voltammetric behavior of the molecule can be discussed in detail at the molecular scale. The results demonstrate the utility of the real-time infrared monitoring in analyzing electrochemical reactions.
In situ Spectroelectrochemical Study of the Anodic Dissolution of Silicon by Potential-Difference and Electromodulated FT-IR Spectroscopy
Authors: Ozanam F. , Da Fonseca C. , Rao A. Venkateswara , Chazalviel J.-N.
Published: October 2003

The anodic dissolution of p-Si has been investigated by in situ infrared spectroscopy. The combination of potential-difference and electromodulated spectroscopies allows for the acquisition of a rather complete picture of the various regimes of the dissolution. After a review of general principles for studying electrochemical interfaces, a study of the interfacial oxide layer formed in the electropolishing regime is presented. Quantitative analysis shows that the thickness and quality of the oxide (density and defect content) depend upon electrode potential. Free-carrier absorption detected in electromodulated spectra shows that the blocking character of the oxide is correlated with the buildup of a stoichiometric oxide of low defectivity at sufficiently positive potentials. Furthermore, the dynamic response to the modulation reveals that oxides formed at weak positive potentials interact with electrolyte species through electro-induced adsorptions/desorptions on charged SiOH sites. At more positive potentials, charge is transported across the oxide by charged defects which could be associated with tricoordinated, positively charged SiO species. Finally, results obtained during porous silicon formation at weak positive potentials are presented. Potential-difference spectroscopy indicates that the electrode exhibits a very large specific surface area, and that the surface is covered by SiH bonds. Electromodulated infrared spectroscopy reveals that the SiH species are generated upon anodic current flowing and that the breaking of these bonds is the rate-limiting step of the anodic reaction. These unexpected results have given rise to the elaboration of new microscopic models for the direct anodic dissolution of silicon in fluoride electrolytes.
Two-Dimensional Infrared and Near-Infrared Correlation Spectroscopy: Applications to Studies of Temperature-Dependent Spectral Variations of Self-Associated Molecules
Authors: Ozaki Yukihiro , Liu Yongliang , Noda Isao
Published: October 2003

This paper demonstrates the potential of generalized two-dimensional (2D) Fourier transform (FT) infrared (IR) and near-infrared (NIR) correlation spectroscopy in the studies of temperature-dependent spectral variations of self-associated molecules. Three examples of the 2D correlation analysis are discussed in this paper. The first two are concerned with the temperature-dependent IR and NIR spectral changes of N-methylacetamide (NMA) in the pure liquid state. The 2D IR correlation approach revealed that almost all the peaks of NMA in the 3400–1100-cm−1 region consist of two to four separate bands. For example, the amide I band contains contributions from at least four distinct bands at 1685, 1665, 1650, and 1635 cm−1. The analysis of the asynchronous 2D IR spectrum in the amide I region showed that the sequence of spectral intensity change in the ascending order of temperature was given by 1635<1650<1665<1685 cm−1. These bands at 1635, 1650, 1665, and 1685 cm−1 were assigned to the amide I modes of chain oligomers of various sizes and dimer of NMA; the longer the chain, the lower the frequency. The closeup view of 2D NIR correlation spectra of NMA obtained at narrow spectral and temperature windows enabled us to propose not only band assignments in the 6800–6050-cm−1 region but also a detailed mechanistic picture of the thermally induced dissociation of NMA for each temperature range. We also applied the generalized 2D correlation approach to the analysis of a set of FT NIR spectra of oleyl alcohol under temperature variations. The 2D NIR analysis enhanced the spectral resolution and simplified the spectra with overlapped bands. For example, it was found that a band at 7090 cm−1 arising from the first overtone of an OH stretching mode of the monomeric alcohol consists of two bands due to the rotational isomerism of the free OH group. An intriguing possibility of correlating various overtone and fundamental bands to establish unambiguous assignments was also suggested from the 2D NIR study on oleyl alcohol.
Incident Angle Dependence of the Infrared Absorbance of Thin Rubbed Polyimide Films on CaF2 and Si Substrates
Authors: Sakamoto K. , Arafune R. , Ushioda S.
Published: October 2003

We have measured the incident angle dependence of the infrared (IR) absorption of thin rubbed polyimide films on CaF2 and Si substrates. The molecular orientation of the films was determined by fitting the experimental result with a theoretical calculation. The incident angle dependence for the rubbed film on CaF2 was very different from that for the rubbed film on Si. On the other hand, the actual molecular orientation determined by the fitting procedure is similar in both samples. Thus this result clearly shows that the incident angle dependence is strongly dependent on the substrate. This effect arises from the interference between the forward and backward propagating light in the film. This experiment demonstrates that the interference effect must be taken into account in determining the molecular orientation of thin films on solid substrates. We have also calculated the incident angle dependence for rubbed films with different inclination angles of polyimide chains on CaF2 and Si substrates. We found that CaF2 is a more suitable substrate than Si for determining the molecular orientation of rubbed films with a relatively high inclination angle of polyimide chains.