bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Aviation Turbine Fuel Composition by Laser Raman Spectroscopy
Authors: Chung W. M. , Wang Q. , Sezerman U. , Clarke R. H.
Published: July 2005

We have applied a Raman spectroscopic approach to the analysis of aviation fuel mixtures. The fuel mixtures chosen are fuels blended to military specification, namely, JP-4, JP-5, JP-7, and JP-8. We expect that the Raman spectral bands from such fuel mixtures may serve to provide a clear and reproducible standard for the determination of fuel properties, suitable for the evaluation of both commercial and military aviation fuel products.
Infrared Study of Tetraalkylurea in Carbon Tetrachloride and/or Hexane and in Chloroform and/or Hexane 1% Solutions
Authors: Nyquist Richard A. , Luoma Davin A.
Published: July 2005

This study indicates that intermolecular complexes exist between tetraalkylurea and carbon tetrachloride and between tetraalkylurea and chloroform. The type of complex or complexes formed is dependent upon the mole % CCl4/C6H14 or mole % CHCl3/C6H14. Intermolecular hydrogen-bonded complexes between tetraalkylurea and chloroform (such as I; I and II; II and III; and III) are formed as the mole % CHCl3/C6H14 increases. The steady decrease in the vC=O frequency is attributed in part to the bulk dielectric effects of the solvent system.
Analysis of Thin-Layer Chromatography Spots by Thermal Desorption/Fourier Transform Infrared Spectrometry
Authors: Chen Xiao , Smart Ronald B.
Published: July 2005

A method is described for obtaining Fourier transform infrared (FT-IR) absorbance spectra of substances separated on silica gel thin-layer chromatographic (TLC) plates. The separated TLC spot is scraped off and loaded onto the sample pan of a thermogravimetric analyzer (TGA)/FT-IR. The FT-IR spectrum of the sample is obtained after the sample is thermally desorbed from the silica gel. Spectra are easily identified for samples present at level of 20 μg per TLC spot. A detection limit of 0.8 μg is reported for analysis of methyl benzoate. The total time required for sample preparation and thermal desorption/FT-IR analysis was six to seven minutes. The relationship between the spectrum peak intensity and the furnace heating rate was also studied. This method can be applied to thermally stable substances which can be desorbed from thermally stable TLC stationary phases.
Diffusion and Preferential Adsorption of Sol-Gel Glass
Authors: Watson J. , Zerda T. W.
Published: July 2005

Samples of porous glass of 38 Å average pore size are prepared with the use of the sol-gel technique. After stabilizing at 800°C, samples are impregnated with various binary mixtures and Raman spectroscopy is used to analyze the composition of the mixtures inside the pores. In order to study the effect of surface interaction on preferential adsorption, the experiments are repeated for samples of modified surfaces. It is shown that surface interactions are important and they determine the excess adsorption. The diffusion rate inside porous glass is also measured and it is shown to depend on surface interactions.
Preliminary Studies of Analytical Applications of a Novel Magnetron Glow Discharge Plasma
Authors: Brewer Stephen , Holbrook Teresa , Shi Zhan , Trivedi Ketan , Sacks Richard
Published: July 2005

The application of a magnetron glow discharge plasma, previously described, to the analysis of six zinc-base NIST Standard Reference Materials for a minor element, aluminum, and three trace elements, magnesium, nickel, and manganese, is described. The wide range of argon pressures, from 0.0007 to more than 2.5 Torr, over which the plasma can be operated, allows selection of optimum pressure for determination of each element. Line-to-background ratios are examined as functions of pressure for each element determined at discharge currents ranging from 100 to 400 mA. Sensitivities of net line intensities to discharge current show wide variations, depending on the element and line studied. Analytical curves for aluminum, magnesium, manganese, and nickel are shown. Detection limits for manganese and nickel are 0.0060% and 0.00055%, respectively.
The Effect of Mode Distribution on Evanescent Field Intensity: Applications in Optical Fiber Sensors
Authors: Colin T. B. , Yang K.-H. , Stwalley W. C.
Published: July 2005

This paper discusses the theoretical and experimental implications of changing the distribution of energy among the guided modes of an optical fiber. Particular emphasis is placed on optimizing the intensity of the evanescent field for near-infrared sensor applications. Both theoretical and experimental results show that, by the shifting of energy from low-to high-order modes, the evanescent field can be enhanced by as much as an order of magnitude. A second benefit of adjusting the mode distribution through mode scrambling is the generation of a stable mode distribution which is relatively insensitive to minor changes in the fiberoptic launch conditions. Therefore, mode scrambling can provide a more stable and more sensitive evanescent field sensor suitable for spectroscopic applications.
Depth Profile Analysis of Flame-Treated Poly(Vinyl Fluoride)
Authors: Hong J. W. , Lando J. B. , Koenig J. L.
Published: July 2005

Chemical and physical changes produced by flame treatment of PVF film have been studied by FT-IR/ATR. By selection of appropriate reflection conditions, the ATR spectra of surface layers corresponding to different depths of penetration of the infrared beam have been recorded. ATR spectra show evidence that the concentration of fluorine and hydrogen species in the amorphous phase of the polymer and of unsaturated functional groups decreases with flame treatment. On the basis of this evidence, it is believed that elimination of a weak surface boundary layer is largely responsible for the improved adhesive properties found for flame-treated samples. ESCA and contact angle measurements have also been performed, and the results of both methods of surface characterization support these conclusions.
Estimating Detection Limits in Ultratrace Analysis. Part I: The Variability of Estimated Detection Limits
Authors: Stevenson Christopher L. , Winefordner James D.
Published: July 2005

The limit of detection (LOD) of a trace analytical method is often used as a gauge of the sensitivity of the method. Improvements and comparisons of similar methods usually involve comparisons of the LODs. However, the calculated LOD value is sensitive to a number of factors such as the method of calculation used, the choice of calibration standards, and the number background (blank) measurements. In this paper, the calculated LOD of a particular analytical method is viewed as an estimate of the true, unknown LOD. Factors which affect the variability of the estimate are investigated. Knowledge of the variability of the estimated LOD can help when analytical methods are being compared on the basis of LOD values. In addition, by knowing which experimental factors contribute to the uncertainty in the calculated LOD, it is possible to determine the analytical protocol which estimates the true LOD most efficiently with no loss in precision.
Improved Supercritical Fluid Chromatography Mobile-Phase Tolerance with a Moderate-Power Helium Microwave-Induced Plasma
Authors: Webster Gregory K. , Carnahan Jon W.
Published: July 2005

Studies comparing the use of moderate (500 W) and low (60–150 W) power helium microwave-induced plasmas (MIPs) for packed-column supercritical fluid chromatography (SFC) are presented. In the 100 to 220 atm SFC pressure range, the low-power plasma exhibits greater signal reduction due to the SFC mobile phase. Plasma characteristics such as helium line intensities and electron densities remain unaltered in the 0 to 120 mL/min (atmospheric pressure volumes) flow rate range with the 500-W helium MIP. As well, Cl(II) emission intensity at 479.45 nm is not affected in this flow rate range. Finally, it is shown that the SFC peak area is not affected as the chromatographic pressure is increased from 150 to 250 atmospheres.
Design and Properties of New IR Liquid Cells with Free Access to the Reaction Volume: Application to Temperature-Dependent Studies of the (Photo)reactions of Some Transition Metal Carbonyls
Authors: Schilder P. G. M. , Luyten H. , Stufkens D. J. , Oskam A.
Published: July 2005

This article describes the construction and properties of new infrared cells for low- and room-temperature studies of (photo)chemical reactions. Both cells consist of three components— viz., a reaction vessel, an IR measurement cell, and a suction unit—which are interconnected by tubes, thus forming a closed system. The main advantages of the cells are that gaseous products of (photo)reactions can be removed and reagents can be added at a later stage of the reaction or at low temperature. The free access to the reaction vessel also facilitates sampling from the IR solution for analytical purposes. These great advantages are demonstrated by a few representative (photo)reactions of transition metal carbonyls.
Characterization of an Alternating-Current Plasma Source for Atomic Emission Spectroscopy
Authors: Colón Luis A. , Barri Eugene F.
Published: July 2005

Results on the characterization of a helium alternating-current plasma (ACP) are presented. Spectroscopic techniques were utilized to obtain diagnostic measurements of the plasma. The characteristics studied include appearance, excitation temperature, ionization and electron temperature, electron number density, and interferences from other concomitants. Sample introduction was achieved with a glass frit nebulizer (GFN). Enhancement of the calcium response was observed while sodium was present in the plasma. Signal depression was noted when calcium and phosphate were simultaneously introduced into the ACP.
Raman Spectroscopy of Mineral Oil Products. Part I: NIR/FT-Raman Spectra of Polycyclic Aromatic Hydrocarbons
Authors: Schrader Bernhard
Published: July 2005

Polycyclic aromatic hydrocarbons (PAHs) are regarded as belonging to the most hazardous compounds in some exhaust gases. Their identification has been difficult since most analytical methods suffer from low specifity or low sensitivity. Raman spectra of polycyclic aromates are expected to show typical fingerprint patterns. However, they could not be recorded with excitation in the visible range of the spectrum since fluorescence was excited instead, with a quantum yield several orders of magnitude larger. The great advantage of the new NIR/FT-Raman spectroscopy is that fluorescence of most compounds cannot be excited, because the energy of the exciting light quanta at 1064 nm is only 46% of the quanta at 488 nm. This paper demonstrates that polycyclic aromates with 4 to 7 rings show very strong and sharp Raman lines. Their distinct patterns supply a powerful tool for identification and multicomponent analyses of PAHs.
Determination of Gas Temperatures at 295–1273 K Using CO Vibrational-Rotational Absorption Spectra Recorded with an FT-IR Spectrometer
Authors: Medvecz Patrick J. , Nichols Kenneth M. , Clay David T. , Atalla Rajai
Published: July 2005

Fourier transform infrared absorption spectroscopy has been used to determine the rotational temperatures of high-temperature (≤1273 K) CO/N2 gas samples. To achieve this objective, a special gas cell was constructed which permitted the acquisition of absorption spectra of samples containing CO at concentrations of 1–10% by volume in N2 and at temperatures between 295 and 1273 K. The absorption spectra were recorded with the use of a moderate-resolution (0.25 cm−1) FT-IR spectrometer. The rotational temperatures were calculated from the spectra after rigorous correction for photometric errors. Temperatures calculated from the P branch of CO spectra had accuracies of 3.2% or better. In all cases, the calculated temperatures were lower than temperatures recorded with a thermocouple, which had an accuracy of ±0.75%. An important factor in the success of these determinations was the adoption of measures to prevent the modulated spectral emission of the hot gases from reaching the detector.
High-Resolution Optical Emission Spectroscopy of Uranium Hexafluoride in the Argon Afterglow Discharge
Authors: Zamzow D. , Murray G. M. , D'Silva A. P. , Edelson M. C.
Published: July 2005

Uranium atom and ion emission spectra resulting from the introduction of gaseous uranium hexafluoride (UF6) into an atmospheric-pressure argon afterglow discharge source have been acquired with the use of a high-resolution spectrometer. The isotopic splitting (235U/238U) of the uranium ion line at 424.437 nm has been utilized to analyze three different UF6 samples containing 0.245%, 3.80%, and 51.20% 235U, respectively. A limit of detection for UF6 in argon of ∼15 ppm for the U(II) 424.167-nm line has been achieved.
Impulse Photopyroelectric Depth Profiling of Multilayers. Part I: Theory
Authors: Power J. F.
Published: July 2005

The theory of time domain (impulse) photopyroelectric effect spectroscopy has been extended in this work to accommodate optically inhomogeneous samples through a derivation of the photothermal Green's function for an optically multilayered system. An analytical solution is obtained for the case of a thermally homogeneous sample layer with an arbitrary optical absorption profile. This solution does not degrade with depth below the sample surface, a common disadvantage of photothermal methods which use transform techniques to recover absorption coefficient profiles. The present theory is generally applicable to photopyroelectric effect measurements on a range of optically inhomogeneous specimens including thin films, and glasses, and may be applied to studies of chromophore migration in thin layers.
A Field-Deployable Dual-Wavelength Fiber-Optic pH Sensor Instrument Based on Solid-State Optical and Electrical Components
Authors: Jones Thomas P. , Coldiron Shelley J. , Deninger William J. , Porter Marc D.
Published: July 2005

The construction, operation, and performance characteristics of a compact, dual-wavelength, solid-state photometer and fiber-optic probe for use with absorbance-based thin-film chemical sensors are described. The instrument has been specifically designed for field deployment and uses low-cost components while maintaining a precision and accuracy comparable to fluorescence-based laboratory sensors. The computer-controlled photometer employs red and green light-emitting diodes (LEDs) as fixed-wavelength light sources and silicon photodiodes as detectors, and has no moving parts. Graded refractive index lenses control light propagation through a beamsplitter in the photometer and through the fiber-optic probe. The beamsplitter directs light simultaneously onto a sample and a reference detector in a double-beam in-space mode which compensates for fluctuations in the outputs of the LEDs. A chemically modified polymeric film is mounted on the fiber probe, and serves as an optical pH sensor. The previously described sensing film is constructed by the immobilization of the diprotic acid-base indicator Congo Red at a base-hydrolyzed cellulose acetate film and responds to changes in pH between 0 and 4.2. An absorbance-based internal calibration scheme, which takes advantage of the optical properties of each of the reactive forms of the immobilized indicator, is presented. The potential capability of this instrumentation, based on its small size and minimal need for calibration, to function as a durable low-maintenance pH sensor for on-site deployment in environmental monitoring applications, is discussed.
Diffuse Reflectance Infrared Spectroscopy Investigations of the Thermal Decomposition of Hexacarbonyl Molybdenum (0) Entrapped in Faujasite-Type Zeolites
Authors: Brémard C. , Depecker C. , Grousilliers H. Des , Legrand P.
Published: July 2005

The temperature-programmed decomposition of Mo(CO)6 entrapped in the faujasite-type zeolites Na85X, Na56Y, and Y* has been investigated with the use of in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) as a function of the Si/Al ratio of the zeolites and the Mo(CO)6 loading level. These investigations were undertaken either under dynamic vacuum or in an atmosphere of CO or He. Evidence is presented for a reversible, sequential decomposition of Mo(CO)6 to Mo(CO)3 and then a one-step irreversible decomposition of Mo(CO)3 to Mo-metal aggregates. The Mo(CO)5 and Mo(CO)4 transient species appeared the most clearly under reduced CO pressure. The Na85X zeolite with high aluminum content (Si/Al = 1.26) promotes an easy decomposition of Mo(CO)6 to Mo(CO)3 at room temperature and stabilizes this adsorbed subcarbonyl species at temperatures above 500 K. A decrease of the aluminum content (Si/Al = 2.5) in Na56 Y increases the decomposition temperature of Mo(CO)6 and decreases the stability of the Mo(CO)3 species. The thermal behavior of Mo(CO)6 entrapped in dealuminated zeolite Y* (Si/Al = 75) was found to be analogous to that of Mo(CO)6 in the gas and solid phases.
Reduction of Acoustic Noise in ICP Emission by the Addition of a Chimney
Authors: Easley Stuart F. , Monnig Curtis A. , Hieftje Gary M.
Published: July 2005

Noise-amplitude spectra were measured for inductively coupled plasma (ICP) atomic emission spectrometry. These spectra indicate that a significant reduction of noise in the emission signal can be obtained by positioning a chimney over the ICP discharge. In this fashion, noise was reduced in the 200–500 Hz region of the frequency spectrum. The chimney had little effect on flicker (1/ f) noise.
Infrared Micro-Imaging of Atherosclerotic Arteries
Authors: Kodali Dharma R. , Small Donald M. , Powell Jay , Krishnan K.
Published: July 2005

Micro-FT-IR spectroscopy is a versatile technique that enables the user to obtain high-quality spectra on small samples. This technique is employed to probe the subcellular chemical composition of atherosclerotic arterial walls and create three-dimensional images representing changes in the composition. Two different rabbit model systems that produced atherosclerosis, either due to genetic disorder or due to physical injury, are studied. The FT-IR spectra are collected from a 20- × 20- μm area of 5- μm-thick arterial section, which is smaller than a single cell. The presence of cholesterol esters and other ester-containing compounds is identified from the -O-C=O stretching (1735 cm−1) absorption, and the cis unsaturation in the acyl chains of these compounds is represented by C=C-H stretching (3005 cm−1) absorption. The protein content is indicated by the intensities of the amide I (1650 cm−1) band. The data clearly show the changes occurring in the chemical composition of an arterial wall, varying with the physiological and morphological changes within the artery and the arteries from different animal models. The power of this technique is demonstrated by excellent correlation with the hot stage polarizing microscopy technique, used to characterize the arterial lipids in situ. The three-dimensional images of the arterial walls, indicating the concentration of different chemical constituents, are very useful in understanding the mechanism of atherosclerosis development.
A Low Stray Light Raman Microprobe Using Optical Fibers and GRIN Lenses
Authors: Jiaying Ma , Zhong Lin
Published: July 2005

The demonstrated Raman microprobe uses optical fibers and GRIN lenses to focus an exciting laser and record Raman scattering. Due to the small size of the optical components, the two parts are spatially separated; therefore much specular light or diffused light is removed from the collected light. Five collecting channels are used to increase the collecting efficiency. Experiments show that the stray light is efficiently reduced and the intensity of the Raman signal is more than ten times higher than the intensity of the spectrum obtained with a conventional Raman microscope. An exciting spot of less than 9 μm in diameter is obtained.
Quantitative Analysis of Powdery Sample by Diffuse Reflectance Infrared Fourier Transform Spectrometry: Determination of the α-Component in Silicon Nitride
Authors: Tsuge Akira , Uwamino Yoshinori , Ishizuka Toshio , Suzuki Kazuo
Published: July 2005

An application of diffuse reflectance infrared Fourier transform (DRIFT) spectrometry to determine powdery sample with an unknown particle size has been proposed. The usefulness of this technique has been demonstrated for the analysis of the α-component in Si3N4 powders. The particle size of the α-component in Si3N4 powder could be determined by measuring the peak intensity ratio between two peaks (500 and 690 cm−1) on the DRIFT spectrum, and the concentration could be determined by comparing the peak intensity to that of standard α-Si3N4 with same particle size. The particle sizes and concentrations obtained by the DRIFT method were in good agreement with those obtained by the light-scattering method and x-ray diffractometry, respectively.
Myoglobin Oxygen Binding Curves Determined by Phosphorescence Quenching of Palladium Porphyrin
Authors: Kelly Jeffrey J. , Kelly Katherine A. , Hartley Sean A. , Barlow Clyde H.
Published: July 2005

A completely optical method was developed for evaluating myoglobin-oxygen saturation. Solution oxygen concentrations were computed from measurements of phosphorescence decay of a soluble palladium porphyrin according to the Stern-Volmer quenching relationship. Visible absorption spectra were recorded of myoglobin solutions progressively deoxygenated by bacterial aerobic metabolism. Myoglobin oxygenation curves were obtained from the spectra by two full-spectrum procedures, singular value decomposition (SVD) and curve fitting, and by the traditional dual-wavelength isosbestic method. The calculated P50 for horse heart myoglobin at 24 ± 1°C was 1.2 Torr by SVD, 1.2 Torr by curve fitting, and 1.4 Torr by dual-wavelength spectroscopy. These results compare favorably with a value of 1.1 Torr estimated from the work of Rossi-Fanelli and Antonini for human myoglobin. The Hill coefficient, theoretically 1.00 for myoglobin, was experimentally determined to be 0.96 by SVD and 0.95 by curve fitting of the spectral data matrix.
Monte Carlo Study of the Relationship between Atom Density and Absorbance in Electrothermal Atomizers
Authors: Güell Oscar A. , Holcombe James A.
Published: July 2005

This work attempts to evaluate the generalized assumption that the electrothermal atomization absorbance signal is proportional to the gas-phase density throughout the transient profile. Spectral line shape considerations (i.e., Voigt profile and hyperfine structure) are introduced into a Monte Carlo simulation model to exploit the time and spatial density and temperature information made available from the simulation. The absorbance is found to be nearly proportional to gas-phase density at low analyte densities—in agreement with generalized assumptions. At higher concentrations the similar linewidths for the absorption and emission profiles reduce the absorbance signal and linear dynamic range. In general, furnace nonisothermality does not produce spectral results noticeably different from those observed with isothermality heated tubes. The temperature-dependent spectral changes for a nonisothermally heated furnace can be closely approximated in most cases by considering only the temperature at the center of the tube.
Spatial Characterization of the Atmospheric-Pressure Moderate-Power He Microwave-Induced Plasma
Authors: Pak Yong-Nam , Koirtyohann S. R.
Published: July 2005

Three-dimensional emission profiles of several metallic and nonmetallic elements from a moderate-power (450 W) atmospheric-pressure helium microwave-induced plasma (He MIP) are presented. A torch using a tangential flow for plasma centering was developed, but the initial goal of forming a stable annular plasma was not achieved. Helium emission gave a symmetrical distribution with maximum emission in the center of the plasma both radially and longitudinally. Calcium atomic emission reached its longitudinal maximum about 3 mm from the cavity bottom and was radially much broader than most nonmetals. The maximum metal ionic emission occurred about 6 mm above the cavity bottom. Maximum chlorine emission occurred still higher and was not affected by nebulized water in the plasma. Emission distribution and behavior suggests that different excitation mechanisms exist for metals and nonmetals.
Densitometry on Thin-Layer Chromatographic Plates by Fourier Transform Near-Infrared Spectrometry
Authors: Yamamoto H. , Yoshikawa O. , Nakatani M. , Tsuji F. , Maeda T.
Published: July 2005

Direct measurement by Fourier transform near-infrared (FT-NIR) spectrometry on thin-layer chromatographic plates is described. Zones separated on a high-performance thin-layer chromatographic plate fixed on the sample stage of a microscope linked with an FT-NIR spectrometer were scanned with a narrow beam of light (0.4-mm square). The NIR chromatogram and spectra of the separated zones were then obtained by the diffuse transmission method. Three kinds of phospholipids that have essentially no absorption bands in the ultraviolet and visible regions but that do have native absorption bands in the NIR region were used to evaluate the usefulness of this method. The limit of detection for phosphatidylcholine was under 1 μg, and the correlation coefficient of the calibration curve obtained from derivative spectra was 0.998 for amounts from 1.25 to 10 μg.
Effect of Solvent Polarity and Acidity on Fluorescence Emission Fine Structures of Select Aza-Polynuclear Aromatics and Dibenzo[b,n]Perylene Hetero-Atom Derivatives
Authors: Tucker Sheryl A. , Acree William E. , Tanga Mary J. , Zander Maximilian , Fetzer John C. , Tokita Sumio , Hiruta Kimihiro , Kitahara Kiyoshi , Nishi Hisao
Published: July 2005

Fluorescence emission spectra are reported for 1-azabenz[a]anthracene, 2-azabenz[a]anthracene, 9-azabenz[a]anthracene, 4-azachrysene, 1,2,7,8-tetraazacoronene, dibenzo[2,3:10,11]perylo[1,12bcd]furan, dibenzo[2,3:10,11]perylo[1,12bcd]thiophene, and dibenzo[2,3:10,11]perylo[1,12bcd] selenophene dissolved in various organic solvents. Results of these measurements are used to classify the solutes into probe or nonprobe molecules depending upon whether emission intensity ratios vary systematically with solvent polarity. Of the eight aromatic solutes examined, only the three azabenzanthracenes showed slight probe character.
Applications of Ultraviolet Resonance Raman Spectroscopy: Residual Olefins in Polypropylene
Authors: Killough P. M. , Devito V. L. , Asher S. A.
Published: July 2005

Ultraviolet resonance Raman spectroscopy is used to probe residual olefin in polypropylene. Ratios of the olefin band to nonresonantly enhanced polymer modes increase with increasing; olefin content. No UV photodamage is evident for samples which are moved through the laser beam. In contrast, an increase in intensity of the olefin band as a function of irradiation time is seen in stationary samples of polymer, which probably indicates photo-oxidative degradation.
A Low-Cost Reflectance FT-IR Microscope
Authors: Jansen J. A. J. , Van Der Maas J. H. , De Boer A. Posthuma
Published: July 2005

A Fourier transform infrared spectroscopy (FT-IR) microscope combines microscopy with infrared (IR) spectroscopic molecular characterization. IR microspectroscopy presents a well-established and useful analytical tool, though at relatively high cost. A low-cost reflectance FT-IR microscope has been developed. The configuration consists of a diffuse reflectance cell, extended to include a diaphragm, a monocular, and an x-y-z stage in combination with an FT-IR spectrometer. The experimental setup is presented in detail. The assembly attains a spot size of 0.3 mm and detection limits in the nanogram range. The potentialities and applications of the low-cost reflectance FT-IR microscope are demonstrated by various examples in the field of polymeric material and product characterization.
Spark Spectroscopy Using Charge Transfer Devices: Analysis, Automated Systems, and Imaging
Authors: Pomeroy Robert S. , Jalkian Rafi D. , Denton M. B.
Published: July 2005

An atomic emission spectroscopic system utilizing a spark source for excitation has been developed. The instrument employs a custom echelle spectrometer and a charge injection device (CID) array detector system. This system simultaneously covers wavelengths from 200 to 450 nm with a resolution of 0.02 nm at 300 nm. Solids sample analyses of steels and aluminums were used to demonstrate this system's speed, sensitivity, and flexibility. Automated systems for rapid qualitative and semi-quantitative screening of these materials will also be discussed. Another spectroscopic system based on a commercial imaging spectrograph and a charge-coupled device (CCD) array detector has been used to obtain temporally resolved spectral images of single sparks discharges.
X-Ray Photoelectron Spectroscopic Studies of Carbon Fibers. Part XV: Electrochemical Treatment on Pitch-Based Fibers by Potentiostatic and Galvanostatic Methods
Authors: Xie Yaoming , Sherwood Peter M. A.
Published: July 2005

DuPont E-120 high-modulus pitch-based carbon fibers were treated on both an electrochemical standard cell system and a pilot plant system under potentiostatic and galvanostatic operation modes. X-ray photoelectron spectroscopy (XPS) and x-ray diffraction (XRD) techniques were used to monitor the fiber surface chemistry and bulk structure changes brought about by the electrochemical treatments. On both the standard cell and pilot plant systems, galvanostatic treatments gave more reproducible changes to the surface and bulk chemistry of the carbon fibers than did potentiostatic treatments. The difference was more obvious when the fibers were treated for a short period of time (less than one minute). The pilot plant system allows the fibers to be treated continuously to obtain a large amount of surface-modified fibers, enabling composite samples to be prepared. The work shows that operating the pilot plant system under a galvanostatic mode allows us to obtain a much more evenly treated fiber surface along the length of the fiber tow.
Detection of Silver Oxide Film Sandwiched in a Multilayer Dielectric Stack by Raman Spectrometry
Authors: Nandra S. S. , Bandekar J. , Cholli A. L.
Published: July 2005

Experiments were performed to detect the presence of thin silver oxide films by Raman spectrometry. Samples consisted of multilayer stacks of ZnO/Ag/ZnO films deposited on glass substrates by a sputtering process. A range of samples was produced where the sandwiched Ag film was protected and unprotected from oxidation during the deposition of the top ZnO film. Raman spectra showed that the individual oxide layers of ZnO and Ag-O on glass substrates had characteristic bands in the spectra. Analysis of the stacks indicated that the samples in which the Ag film was unprotected during the deposition of the top ZnO showed the presence of a typical Ag-O band. It was concluded that Raman spectroscopy is a sensitive, nondestructive technique for the detection of silver oxide layers in a multilayer system.
The Application of NIR Spectroscopy for the Prediction of Properties of Australian Refined Reformate
Authors: Asker N. , Kokot S.
Published: July 2005

A rapid NIR method for the determination of octane number of reformate samples of Australian refined motor gasoline is described. Results of predictions using calibration sets based on ASTM full blends and actual reformate samples are presented. Interpretation of spectral data using principal component analysis facilitates the selection of a suitable analytical spectral range and demonstrates that the reformate samples may be distinguished on the basis of the geographical origins of the parent crude oils. The described method forms a basis for practical application and is a possible alternative to the standard CFR engine test method.
Detection of Benzo[a]Pyrene Metabolites by Laser-Excited Shpol'skii Spectrometry
Authors: Weeks S. J. , Gilles S. M. , D'Silva A. P.
Published: July 2005

Chemical carcinogenesis studies mandate isomer-selective detection at ultratrace levels of the metabolites of polycyclic aromatic compounds (PACs). The formation of hydroxy PACs is a key step in the metabolic process, particularly detoxification, for PACs in mammals. The infamous carcinogen benzo[a]pyrene (B[a]P) and its metabolites are often used as marker compounds to assess human exposure to total PACs and to study the development of cancer. In this work, isomers related to two alternative metabolic pathways for B[a]P have been selectively detected from urine and blood sera samples by laser-excited Shpol'skii spectrometry (LESS). The polar metabolites are derivatized and extracted into the n-alkane Shpol'skii solvent for direct, trace-level, isomer-selective detection. An absolute detection limit for 9-methoxy B[a]P was 50 attomole for a 20- μL sample.
Surface-Enhanced Raman Analysis of Biomedical Eye Lens Extracts
Authors: Sokolov K. V. , Lutsenko S. V. , Nabiev I. R. , Nie Shuming , Yu Nai-Teng
Published: July 2005

This report describes a new application of surface-enhanced Raman spectroscopy (SERS) in the analysis of highly complex and crude biomedical samples. The specific cases examined are ophthalmic extracts obtained from the homogenization of a normal human lens, a senile cataractous human lens, and a chipmunk lens. The results demonstrate that SERS is capable of selectively probing certain biological components with high mass sensitivity. In the chipmunk and normal human lens extracts, adenine-containing molecules (e.g., adenosine-5'-monophosphate) are found to be abundantly present, while intense tyrosine and tryptophan Raman signals are apparent in the SERS spectrum of the cataractous human lens sample. We have also conducted gel-filtration and mass spectrometric studies of the eye lens extracts, and the results indicate that SERS is an effective method for biomedical species identification.
Total Luminescence Spectroscopy in the Identification and Detection of Coumarin (1,2-Benzopyrone) in Road Fuels
Authors: Shanahan Gary J. , Boley Nicholas P. , Traynor Allan D.
Published: July 2005

Total luminescence spectroscopy was used to differentiate between coumarin and other fluorescent compounds in samples of diesel road fuel. With this technique, the presence of coumarin could be confirmed in samples of fuel adulterated with rebated kerosene.
Evaluation of the Appropriate Sample Position in a PAS/FT-IR Experiment
Authors: Carter R. O. , Wright Steven L.
Published: July 2005

The experimental selection of the distance between the sample and the window in a photoacoustic FT-IR experiment is shown to be an important parameter when one is optimizing the interferogram intensity. We have experimentally demonstrated the advantages of selecting a small distance rather than the full boundary layer thickness required to ensure complete conversion of thermal to pressure signal at the sample surface. The minimum volume of the sample chamber is a controlling factor in the optimization of the experiment. In this report we demonstrate the value of minimizing sample chamber volume through controlling sample thickness while pointing out the need for care when doing so.
Infrared Study of Ethylene Carbonate in Various Solvents and Solvent Systems
Authors: Nyquist R. A. , Settineri S. E.
Published: July 2005

The vC=O frequency for ethylene carbonate is in Fermi resonance with the first overtone of the skeletal breathing mode, and the extent of Fermi interaction is affected by solvent/solvent interaction. The vC=O frequencies have been corrected for Fermi resonance, and the corrected vC=0 frequencies have been correlated with the mole % CHCl3/CCl4, (CH3)2SO/CCl4,(CH3)2SO/CHCl3, and CHCl3/ n-C6H14, the solvent reaction field, and vC=O for acetone recorded in the same solvents. Solute/solvent interactions are discussed. The acceptor number of the solvent vs. the vC=O frequencies apparently correlates in a different manner for the solvents which form intermolecular hydrogen bonds with the solute. Steric factors are suggested as being one of the reasons that the AN values and vC=O frequencies do not give nonambiguous correlations. The vC=O mode for ethylene carbonate shifts continuously to lower frequency as the mole % CHCl3 or (CH3)2SO increases in each of the solvent mixtures studied.
An Interaction Model for Solid-Matrix Phosphorescence with Filter Paper via the Modulus of Filter Paper
Authors: Hurtubise R. J. , Ramasamy S. M.
Published: July 2005

The experimental values of Young's modulus for filter paper samples were obtained as a function of temperature. These experimental modulus values for the filter paper samples, along with literature modulus values for regenerated cellulose and chromatography paper, were used to derive equations that relate Young's modulus values of filter paper to the phosphorescence lifetimes of adsorbed phosphors on filter paper as a function of temperature. In addition, an equation was derived for one of the phosphors that relates the changes in phosphorescence quantum yield with temperature to Young's modulus. The basis for the equations is a theory for hydrogen-bond-dominated solids that considers Young's modulus as related to the average force constant for the hydrogen bonds in paper and the effective number of hydrogen bonds in paper. For all the systems investigated, linear relationships were obtained between ln(phosphorescence lifetime) and ln(Young's modulus). Also, a linear equation was obtained between ln(phosphorescence quantum yield) and ln(Young's modulus) for one of the phosphors. In general, the results of this work form the basis of a fundamental theory for the phosphorescence of compounds adsorbed on filter paper.
Photoacoustic Depth Profiling of Polymer Laminates by Step-Scan Fourier Transform Infrared Spectroscopy
Authors: Dittmar Rebecca M. , Chao James L. , Palmer Richard A.
Published: July 2005

The use of step-scan Fourier transform infrared (FT-IR) spectroscopy with photoacoustic (PA) detection for depth profiling studies of polymer laminates is demonstrated. Step-scan FT-IR simplifies the extraction of depth profile information due to the single modulation frequency that can be applied over the entire spectral range. Because a single modulation frequency is generally used in step-scan FT-IR, the thermal diffusion length, μ, is constant for all wavelengths in a single scan. In addition, lock-in detection allows for easy extraction of the signal phase. Two methods of depth profiling are discussed and illustrated. The first is the conventional method of varying the probe depth by changing the modulation frequency. The other method depends on the direct use of the signal phase. The phase analysis technique is particularly useful for cleanly separating the signal due to a thin (<5 μm) surface layer from that of the bulk or substrate.
Application of ATR-IR to the Analysis of Surface Structure and Orientation in Uniaxially Drawn Poly(Ethyleneterephthalate)
Authors: Walls Dennis J.
Published: July 2005

A critical examination of the use of ATR-IR for the examination of surface composition and orientation in uniaxially drawn poly(ethyleneterephthalate) (PET) films has been performed. This work has identified the band at 1410 cm−1 as a satisfactory reference band in ATR-IR analyses for surface composition and orientation analyses in oriented PET films. Other commonly used reference bands at 790 and 1510 cm−1 have been shown to be influenced by both incident infrared polarization and orientation within the polymer films. Control of sample clamping pressure in a conventional ATR-IR clamp has been shown to afford optimized sample contact, needed in conjunction with the use of valid reference bands to obtain reproducible in-plane surface dichroism measurements of films with varying degrees of orientation.
A High-Efficiency Light-Collection System for Energy-Limited Infrared Emission Radiometers
Authors: Busch Kenneth W. , Busch Marianna A. , Tilotta David C. , Kubala S. Wayne , Ravishankar S.
Published: July 2005

An optical system that combines radiation from four solid angles about an emission source into a single beam was used in conjunction with a detector-noise-limited, flame infrared emission (FIRE) radiometer to increase the optical throughput of the f/4 polychromator dispersion system. Equations for the optical layout of the four-angle, pre-dispersion optics were derived, and the performance of the system was compared with a traditional, single solid-angle lens system. The four-angle collection optics were found to increase the signal-to-noise ratio of HCl emission at 3.77 μm by a factor of 3.8, in agreement with the theoretically expected value. The signal-to-noise performance expected for detector-noise-limited conditions, background-shot-noise-limited conditions, and background-flicker-noise-limited conditions is discussed.
FT-IR in Combination with the Attenuated Total Reflectance Technique: A Very Sensitive Method for the Structural Analysis of Polypeptides
Authors: Singh Bal Ram , Fuller Michael P.
Published: July 2005

We have used Fourier transform infrared spectroscopy to analyze protein structure at nanomolar concentrations and compared its sensitivity with other commonly used spectral techniques such as circular dichroism and fluorescence. Less than 10 nM concentration of protein (immunoglobin G) was required in order to obtain IR spectra with good signal-to-noise ratio that could be utilized for curve-fitting analysis to obtain individual band areas assigned to specific secondary structural features. No signals were observable on circular dichroism, and the fluorescence signals were within the noise level for the same concentration of the protein. The results suggest that FT-IR in combination with the ATR technique has high potential for protein structural analysis, and less than 15 picomole protein is sufficient for the structural analysis.
Absolute Analysis in Electrothermal Atomic Absorption Spectrometry: PB with Matrix Modifiers
Authors: Fagioli F. , Locatelli C. , Vecchietti R. , Torsi G.
Published: July 2005

A new method for absolute analysis in Electrothermal Atomization Atomic Absorption Spectroscopy (ETA-AAS), proposed for aqueous solutions, is extended to matrix modifiers based on palladium and magnesium. The experimental results show that only the Pd-based matrix modifier can be accepted for Pb analysis. No differences have been found if tantalum is used instead of graphite as the atomization surface in the same experimental conditions.
Comparison of Heterogeneously and Homogeneously Doped Polyphenylacetylene Using IR and XPS
Authors: Ferraro J. R. , Hill S. , Stout P. , Furlani A. , Polzonetti G. , Russo M. V.
Published: July 2005

Infrared (IR) and x-ray photoemission spectroscopy (XPS) studies have been made on heterogeneously iodine-doped polyphenylacetylene (PPA) polymer films. Similarities and differences between the doping processes (heterogeneous and homogeneous) are presented. Results point to a surface doping process in the heterogeneously doped films vs. a bulk process in the homogeneously doped materials (doped in solution). The counter anion moiety in the films appears to be the polyiodide I5− ion, as contrasted to the bulk powder (homogeneously doped) polymer in which the species of I2, I3− in the presence of a predominance of I5− ion coexist.
Attenuated Total Reflectance Spectra of Colloidal and Particulate Silica Samples in Aqueous Media
Authors: Smith-Palmer Truis , Lynch Brian M. , Roberts Cheryl , Lü Yanjia
Published: July 2005

We have measured and compared ATR/FT-IR spectra of aqueous dispersions of colloidal silica, and aqueous suspensions of particulate silica, over ranges of bulk concentrations using CIRCLE® and Contact Sampler™ cells. Procedures are described for quantitative analyses of each silica type. Detection limits are approximately 0.001% for the particulate species. The spectra of particulates are distorted by refractive-index effects to low frequency of the main analytical bands around 1090 cm-1, but the distortions are proportional to concentration and do not interfere with the precision of analyses. We recommend either ATR cell, but the Contact Sampler™ is more convenient.
A Method for Background Reduction in a Supersonic Jet/Multiphoton Ionization Reflectron Time-of-Flight Mass Spectrometer
Authors: Wang Alan P. L. , Li Liang
Published: July 2005

A method of background reduction for supersonic jet spectroscopy (SJS) and multiphoton ionization mass spectrometry (MPIMS) is described. This method is based on the ion trajectory difference of the sample ions, generated from the jet-cooled molecules, and the background ions during the flight from the acceleration region to the detector in a reflectron time-of-flight mass spectrometer (TOFMS). Studies of the ionization signal profiles of the sample pulse and background indicate that the jet-cooled sample molecules have much higher linear velocities in the jet expansion axis than the background molecules. On the basis of this fact, a computer simulation on the ion trajectory in the TOFMS is performed. The simulation results suggest that it is possible to selectively detect the sample ions if a sufficient flight distance is provided. It is demonstrated that, with a reflectron TOFMS which provides a longer flight length and a less diffused sample-ion packet, the intense background signals can be significantly reduced with the use of an ion deflector and the proper adjustment of the time delay between the laser and the sample pulse. Finally, an example of the application of this method for background reduction in SJS and MPIMS with the fast atom bombardment and laser desorption techniques for sample volatization is given.
Advances in Optical Spectroscopy: The Ultra-Small Sample Analyzer
Authors: Harrick N. J. , Milosevic M. , Berets S. L.
Published: July 2005

A new reflectance accessory has been developed for the spectroscopic analysis of physically small samples and small areas of large samples. This accessory, known as the “Split Pea” accessory (SPA), has several advantages over those currently used for microsampling, i.e., high-pressure diamond cells, microscopes, and beam condensers. The SPA enables nondestructive, internal reflectance studies of microgram and nanogram samples with little or no sample preparation. Its specially configured pressure plate permits the application of high clamping pressures between the sample and the internal reflection element, simplifying the analysis of hard surface solids such as paint chips. The SPA can also be configured for either external or in-line diffuse reflectance, depending on the sample under investigation. The spectra presented here demonstrate the versatility and wide range of applications for this new accessory.
Molecular Orientation of Monolayers on Liquid Substrates: Optical Model and FT-IR Methods
Authors: Fina Leslie J. , Tung Yei-Shin
Published: July 2005

The primary emphasis of this work is on the development of an optical model which is descriptive of the reflection-absorption properties from an anisotropic monolayer located on an isotropic liquid substrate. The calculations of electric field intensities, phase changes, and reflection-absorptions are compared for isotropic and anisotropic monolayers in order to explore optical model predictions of chain anisotropy. Relationships are established between the average chain orientation angle, the anisotropic optical constants, and the angle of incident light for s-and p-polarized radiation. The modeling calculations predict that the optimum incident light angles for the extraction of orientation information occur close to the polarizing Brewster angle. A method is proposed whereby the orientation types of isotropy and chain alignment at the isotropic-equivalent angle can be distinguished.
Determination of the Wavelength Positioning Accuracy of a Sequential Scanning ICP Spectrometer
Authors: Grosser Zoe A. , Collins John B.
Published: July 2005

This work evaluates the wavelength reproducibility and accuracy of a sequential scanning plasma emission system. The long-term thermal and thermomechanical errors are found to be in the range of a few picometers. The short-term instability and mechanical instability are found to contribute very little error to wavelength positioning. The wavelength calibration algorithm is described. Its use improves the accuracy by a factor of 5 to 10 by comparison with results from the use of the diffraction grating equation alone.