bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser-Induced Fluorescence Detection of NH3 in Flames with the Use of Two-Photon Excitation
Authors: Westblom Ulf , Aldén Marcus
Published: June 2005

Laser-Induced Fluorescence (LIF) has been used for the detection of ammonia molecules, NH3, in flames at atmospheric pressure. Excitation was accomplished by a two-photon step from the ground state, X, to the C′ state, with the detection of the fluorescence radiation from the C′ state to the A state. This excitation scheme was also utilized for the simultaneous flame detection of OH and NH3. NO could also be simultaneously detected with the laser beam resulting from frequency mixing of the IR beam and the doubled dye laser beam from a Nd:YAG-based laser system.
Anomalous Contributions to the Signal in Laser-Enhanced Ionization Spectrometry from “Scattered” Laser Light
Authors: Axner O. , Sjöström S.
Published: June 2005

Anomalous contributions to the measured signals in Laser-Enhanced Ionization (LEI) spectrometry in flames is investigated. It was found that a significant part of the one-step LEI signal (»90% in certain cases) can be attributed to ionization of atoms which are positioned outside of the “true” interaction region (the region out-traced by the laser beam in the flame) due to excitation of atoms by “scattered” light (the word “scattered” is here used in its widest meaning, i.e., it refers to scattered, diffracted as well as fluorescence light). This is especially significant when small beam diameters and high light intensities are being used. The anomalous contributions to the LEI signals from “scattered” light are investigated both in a study of the shape (the widths) of one-step LEI signals and in experiments with two nonoverlapping beams in the flame. Several origins for the “scattered” laser light are proposed and investigated: (1) diffraction of laser light from apertures, (2) emitted fluorescence from analyte atoms in the interaction region, and (3) scattering from flame related particles or molecules in the interaction region. The exact mechanism has not yet been determined, but the findings are indicative of some sort of saturable scattering process from a flame constituent which exists in higher concentrations in fuel-rich flames than in lean flames. The existence of “scattered” light outside of the interaction region implies, furthermore, that erroneous conclusions may be drawn when, for example, number densities, ionization yields, signal enhancements, and saturation effects are studied by LEI.
A Pathlength Correction Method for Near-Infrared Spectroscopy
Authors: Miller Charles E. , Naes Tormod
Published: June 2005

A method for correction of pathlength effects in near-infrared (NIR) spectra is presented. This method, called Pathlength Correction with Chemical Modeling (PLC-MC), requires the use of standards in which the chemistry varies but the pathlength remains constant. Principal Components Analysis (PCA) is used to model the chemical variations in the spectra of the standards. The PCA model can then be used to estimate the pathlength of a future sample from the spectrum of the sample. Theoretical and experimental comparisons of the PLC-MC correction method with the Multiplicative Scatter Correction (MSC) method indicate that the PLC-MC method is more accurate than the MSC method if spectral variability from chemical variations is large.
Infrared Study of Coumarin in Different Solvent Systems
Authors: Nyquist Richard A. , Settineri Sam E.
Published: June 2005

Coumarin exhibits two infrared bands in the carbonyl stretching region of the spectrum. The doublet is due to Fermi resonance (F.R.) of the carbonyl stretching mode, vC=O, with an overtone of a lower-lying fundamental. The vC=O mode was corrected for F.R. in a series of solvents and solvent systems, and unperturbed vC=O was correlated with mole % solvent A/solvent B, and other parameters. The cause of shifts of vC=O in solvent systems is the result of several parameters, including bulk dielectric effects, basicity of the carbonyl group, and steric factors of both the solute and solvent.
Analysis of Rigid Polyurethane Foams by Near-Infrared Diffuse Reflectance Spectroscopy
Authors: Miller Charles E. , Eichinger B. E.
Published: June 2005

The method of near-infrared diffuse reflectance spectroscopy is used to determine the compression and thermal properties of rigid polyurethane foams. Principal components analysis (PCA) of the spectra of the foams indicates that NIR spectroscopy can be used to discriminate between foams that were prepared from different polymeric formulations. Partial Least-Squares (PLS) calibrations of NIR spectra to the compression modulus, compression strength, deformation at failure, and K-factor (thermal conductivity) were also done. Results indicate that NIR spectroscopy can determine the compression modulus within 63.6 psi, compression strength within 2.63 psi, deformation at failure within 1.29%, and K-factor within 0.0089 Btu-in./°F-h-ft2.
Study of Distribution of Atoms in Laser-Generated Plumes by Laser-Enhanced Ionization Spectroscopy
Authors: Pang Ho-Ming , Yeung Edward S.
Published: June 2005

Laser-enhanced ionization can be used to interrogate the laser-generated plume. Relatively broad absorption spectral features due to the dense laser plumes have been studied by using two separate lasers to provide different vaporization and excitation conditions. By varying the time delay and the positions between the vaporization and excitation laser pulses, one can study the evolution of the laser-generated plumes. High sensitivity can be achieved even with the use of visible light for excitation.
Charge-Coupled Device Fluorescence Detection for Capillary-Zone Electrophoresis (CCD-CZE)
Authors: Cheng Yung-Fong , Piccard Richard D. , Vo-Dinh Tuan
Published: June 2005

This paper describes a new instrument system combining capillary-zone electrophoresis (CZE) separation and charge-coupled device (CCD) fluorescence detection. The performance of this CCD-CZE system is evaluated and compared with the performance of a photomultiplier tube (PMT) detector, with the use of signal-to-noise (S/N) ratio and acquisition time as measures of performance. The feasibility of on-column fluorescence spectrometric detection is demonstrated, and a three-dimensional electrophorogram is presented to show the spectral and time resolution obtained by injection of 2 femtomoles (5 nanoliters of 4.0 × 10−7 M) of fluorescein into the capillary column. The software uses a “peak sum” method to achieve optimum S/N ration. The limit of optical detection (LOD) for this system is 4 attomoles (4 × 10−18 mole) of fluorescein, with a CCD integration time of only 0.2 s. If the fluorescence signal were integrated for 4 s on the CCD, an LOD of less than 1 attomole could be achieved for fluorescein. A 4-s integration time would still permit three complete spectra during the 30-s elution time of the sample.
Infrared Study of Hexahydrophthalic Anhydride, Halogenated Phthalic Anhydrides, Halogenated Maleic Anhydride and Styrene-Maleic Anhydride Copolymer in Solvent Mixtures
Authors: Nyquist Richard A.
Published: June 2005

The v(C=O)2 modes for carboxylic acid anhydrides decrease in frequency as the solvent solubility parameter value increases. The vout-of-phase(C=O)2 mode for anhydrides decreases more in frequency than the vin-phase(C=O)2 mode in going from CCl4 solution to CHCl3 solution, indicating that it is more difficult for the vout-of-phase(C=O)2 mode to vibrate than it is for the vout-of-phase(C=O)2 mode in the same solvent system. Solute/solvent interaction induces a change in the Fermi resonance interaction between v(C=O)2 and combination and/or overtones of lower-lying fundamentals as the mole % solvent 1/solvent 2 changes.
Carbon-13 NMR Analysis of Pentaerythritol Triacrylate
Authors: Newmark Richard A. , Palazzotto Joyce
Published: June 2005

Ratios of pentaerythritol diacrylate, triacrylate, and tetraacrylate are readily determined from quantitative carbon-13 NMR spectra. In addition, absorptions due to a Michael addition product are quantitatively observed. This dimer is at the 5 to 30 wt % level in typical triacrylate samples.
An Expression for Spectral Line Intensity Data
Authors: Thelin Bo
Published: June 2005

In this paper a new spectral line intensity expression for describing spectral data is shown. Linear graphs were obtained during a study of the logarithm of the following spectral line intensity proportionality:

[Formula: see text]

where hv is the photon energy. These results were obtained from the UV to the IR spectral regions, with the use of standard tables of spectral line intensitites from dc arc experiments. Similar relationships were obtained when an inductively coupled plasma (ICP) was used in combination with a photon-counting IDES system. Support for the exp( hv/kT) term in this expression is given by comparison with another method where spectral line intensity ratio fluctuations are studied with an ICP-IDES system. A linear graph was obtained when spectral line intensity ratio fluctuations were plotted against the differences in photon energies for the spectral transitions. Consequently, two independent methods give support to this expression over a wide spectral range with different kinds of experiments.
The Determination of Isotopically Labeled Species by FT-IR Difference Spectroscopy in the Study of Catalytic Reaction Mechanisms
Authors: Nelson Peter F.
Published: June 2005

The use of FT-IR gas-phase difference spectroscopy for the determination of isotopically labeled species in the study of catalytic reaction mechanisms is illustrated. Applications are based on the study of the mechanism of oxidative coupling of methane over oxide catalysts and include determinations of: (1) deuterated and partially deuterated ethylenes and ethanes from experiments with 2H labeling of the methane; (2) 18O contents of CO and CO2 from experiments with 18O labeling of O2, CO, and CO2; (3) 13C/12C ratios in hydrocarbons and carbon oxides from experiments with 13C labeling of C2 hydrocarbons. The major limitation of the technique is in regions of strong absorption where nonlinear effects make subtraction difficult; however, this limitation could be alleviated by judicious choice of pathlength. This technique is a powerful supplement to measurements based on mass spectrometry.
Enhancement of the Absorptions of Surface Species Present on Graphitized Carbon Fibers: A Theoretical Approach
Authors: Sellitti C. , Koenig J. L. , Ishida H.
Published: June 2005

An oxidized carbon fiber has been modeled as a thin polymeric film, representing the surface species, coated with a graphite overlayer. Optical theory has been utilized to calculate the variations in the electric field intensities that occur when the graphite layer is overlayed on a film of PVAc (polyvinylacetate). The increase of the 〈 E z2〉 component has been observed. Spectral simulations based on Hansen's formulas clearly show the enhancement of the infrared absorbances. The enhancement proves to be dependent on the air gap thickness existing between the germanium element and the polymeric film and on the nature of the substrates.
Time-Domain (Interferogram) and Frequency-Domain (Absorption-Mode and Magnitude-Mode) Noise and Precision in Fourier Transform Spectrometry
Authors: Liang Zhenmin , Marshall Alan G.
Published: June 2005

It is desirable to be able to predict the precision of a repeated measurement, based on the result of a single measurement and knowledge of the noise level in the original (time-domain) data. We have previously shown that precision in determination of time-domain signal parameters (initial magnitude, frequency, and exponential damping constant for a noisy exponentially damped sinusoidal signal) from least-squares fit to a frequency-domain FFT spectrum is directly proportional to frequency-domain peak height-to-noise ratio and to the square root of the number of data points per peak width, with a proportionality constant which depends on the spectral type (absorption mode, magnitude mode) and peak shape (e.g., Lorentzian, Gaussian, etc.). In this paper, we show that precision in determination of those same parameters by least-squares fit to the time-domain signal itself is similarly related to time-domain initial amplitude-to-noise ratio and the square root of the number of data points per damping period. In addition, we show that although magnitude-mode spectral noise is well described by a Rayleigh distribution in the signal-free baseline segments of the spectrum, noise in the vicinity of a magnitude-mode spectral peak is more accurately described by a normal (Gaussian) distribution. We then proceed to show that determination of spectral parameters from a time-domain data set is more precise by a factor of √2 than estimates based on the FT absorption-mode spectrum. We further show that padding of the N-point time-domain data set by another N zeroes before FFT improves frequency-domain absorption-mode precision by the same √2 factor. Additional zero-filling does not improve spectral precision. Zero-filling has no effect on precision of spectral parameters determined from time-domain data, and variable effects on parameters determined from fits to magnitude-mode spectra. The above theoretical predictions are supported by analysis of simulated noisy data.
X-Ray Photoelectron-Spectroscopic Studies of Carbon Fiber Surfaces. Part XII: The Effect of Microwave Plasma Treatment on Pitch-Based Carbon Fiber Surfaces
Authors: Xie Yaoming , Sherwood Peter M. A.
Published: June 2005

X-ray photoelectron spectroscopy has been used to monitor the surface chemical changes on DuPont high-modulus pitch-based carbon fiber surfaces brought about by microwave air-plasma treatments for different periods of time. The air-plasma treatment increased the fiber surface functionalities, but extended treatment caused fiber damage. X-ray diffraction studies showed that the bulk structure was not affected by the air-plasma treatment. XPS valence band spectra proved a more sensitive probe of the surface chemistry of the carbon fibers than XPS core studies. Air-plasma treatment of fibers promises to be an effective method of fiber treatment.
The Intramolecular Loss of Fluorescence by Lysine Derivatized with Naphthalenedialdehyde
Authors: Soper Steven A. , Chamberlin Steve , Johnson Carey K. , Kuwana Theodore
Published: June 2005

Derivatization of primary amines such as amino acids and peptides with naphthalenedialdehyde (NDA) in the presence of cyanide ion yields cyanobenzo[f]-isoindole (CBI) adducts that are highly fluorescent. However, the fluorescence is seriously quenched with amines that possess more than one primary amine site, as is the case with lysine. Although it was found that the adsorption of CBI2-lysine on a solid substrate restored the fluorescence, the reason for the solution quenching, with respect to results for mono-derivatized amines, was investigated. The experiments to probe the quenching were based on the assumption that the mechanism responsible for quenching involved a charge-transfer (CT) excited state. Thus, it was found that the solvent properties of viscosity and polarity affected the lifetime and quantum yield of fluorescence in a manner consistent with the proposed mechanism.
Raman Spectroscopic Identification of Cystine-Type Kidney Stone
Authors: Kodati Venkata Ramana , Tu Anthony T.
Published: June 2005

Two kidney stones of the cystine type (cystinuria stone) were examined by Raman scattering technique by focusing the green laser (514.5 nm) directly on the stones. The scattered Raman shift was examined and compared with that of standard compound, cystine. Almost identical spectra were obtained for the stones and cystine. The most important identification was based on the S-S stretching vibrational band at 498 cm−1. The present investigation indicates that Raman spectroscopy is a simple, rapid, and reliable analytical tool for identifying a cystinuria stone.
Improving Spectroscopic Techniques by a Scanning Multichannel Method
Authors: Knoll P. , Singer R. , Kiefer W.
Published: June 2005

The conventional optical multichannel technique (MT) has improved optical spectroscopy, in comparison to single-channel methods, by at least an order of magnitude in measurement time at the same signal-to-noise ratio. In this work we show that some disadvantages (e.g., limited range of the recorded spectra, different noise and sensitivity of each detection element, and fixed spectral distance of the detection elements) can be excluded by using what we call the scanning multichannel technique (SMT). A calculation of the measurement time for characteristic single-channel and multichannel detectors results in the fact that SMT is, like MT, an order of magnitude faster than the single-channel technique (SCT). In some particular cases SMT results in measurement times shorter than those for MT. We conclude that SMT combines the advantages of MT and SCT. Moreover, measurements of sharp spectral lines made it evident that SMT also improves the reproducibility of the spectrometer used and increases the accuracy of the recorded spectra. The SMT method is not only restricted to optical spectroscopy but can be universally applied to all spectroscopic methods where multichannel detection is used.
Optimization of a Flow Injection Sampling System for Quantitative Analysis of Dilute Aqueous Solutions Using Combined Resonance and Surface-Enhanced Raman Spectroscopy (SERRS)
Authors: Taylor Gordon T. , Sharma Shiv K. , Mohanan Kakkala
Published: June 2005

A flow injection sampling system to analyze dilute aqueous solutions by surface-enhanced resonance Raman spectroscopy (SERRS) is described, and critical operating parameters are evaluated. A simple procedure for preparing a silver colloid, which is more homogeneous, stable, and SERS-active than that previously reported and does not require sedimentation, is presented. With the use of crystal violet (CV) as a model analyte, the flow injection system, a Raman micro-probe, and an optical multichannel analyzer (OMA) for detection, high-quality, highly reproducible (coefficient of variation = ±2.37% of mean) Raman spectra for 1 × 10−6 M solutions of CV were obtained in 1 min, and major spectral peaks were observable down to concentrations of 1 × 10−12 M (∼4 × 10−19 g of material). SERRS enhancement and spectral quality were experimentally found to vary significantly with the method of Ag sol preparation and laser excitation wavelength. The system described can rapidly (1–240 s) provide quantitative as well as structural information about very dilute aqueous solutions.
Evaluation of Sample Introduction Techniques of Packed-Column SFC into an MIP
Authors: Motley Curtis B. , Long Gary L.
Published: June 2005

A packed-column supercritical fluid Chromatograph (SFC) was coupled to an argon high-efficiency microwave-induced plasma (Ar-HEMIP) for the purpose of elemental detection of the chromatographic effluent. Two methods of sample introduction of the effluent into the argon plasma are presented for this hyphenated technique. The results of central introduction vs. sidearm introduction of SFC effluent into the Ar-HEMIP are evaluated according to analytical parameters such as: repeatability, the effects of pressure programming of 100% CO2 and modified CO2 on background emission, linear dynamic range (LDR), and minimum detectable quantity (MDQ) of several organometallic compounds. Sidearm introduction is found to be superior to central introduction in terms of these analytical parameters.
Elimination of Background in Fiber-Optic Raman Measurements
Authors: Myrick M. L. , Angel S. M.
Published: June 2005

A Novel fiber-optic configuration with forward-scattering light collection is used to measure Raman spectra using long optical fibers with little background interference. This probe design allows control over the sample volume, and measurements can be made at considerable distances from the face of the optrode. The properties of this optical configuration are discussed, as well as its advantages and disadvantages. Normal Raman spectra were measured with this technique, with fibers as long as 100 m. The performance of the probe is not affected by highly scattering solutions. A similar technique was used to measure surface-enhanced Raman spectra on Ag electrodes with 250-m fibers.
Infrared Spectra of Tetramethylammonium Halides
Authors: Winnett Kevin
Published: June 2005

Infrared spectra of tetramethylammonium (TMA) halides are discussed with an emphasis on perturbations of the hydrogen vibrational motions caused by anion effects in aqueous solution. The fully deuterated molecule is included in the discussion. The effect of halide anion concentration on the C-H stretching region of the IR spectrum is presented. It is concluded that hydrogen bonding is not the cause of the shift of the wavenumber of these modes.
Error Reduction in Spectrum Estimation by Means of Concentration-Spectrum Correlation
Authors: Mitsuka Yoshihiro , Uozumi Jun , Asakura Toshimitsu
Published: June 2005

A new technique is introduced for reducing the estimation errors accompanying component spectra estimated by means of the concentration-spectrum correlation method. Many estimates of the component spectra, given to different errors, are obtained by the nonparametric statistical method called the bootstrap. Among them, there exists a spectrum that has a very small error. This spectrum can be found by searching for the spectrum that has the least entropy, since a parameter of the entropy is correlated positively with the estimation error. Computer-simulation experiments are performed to demonstrate the effectiveness of the present technique for cases involving both unconstrained concentrations and constrained concentrations whose sum for all the components in a sample is unity.
Transfer of Raman-Scattered Light from Gases by Fiber Optics
Authors: Schopp M. , Schrötter H. W. , Douklias N.
Published: June 2005

In the focus of the argon-ion ring laser of our cw CARS spectrometer, a power of over 100 W is available at 514.5 nm. It has been used here for the excitation of linear Raman spectra of gases. The collected 90° scattering is transferred to the entrance slit of a double monochromator by ordered fiber-optic bundles with slit-like cross sections. The transfer efficiency varies with the slitwidth used; values between 13% and 23% have been achieved. The recorded spectra of nitrogen and air compare favorably with those obtained with conventional extra-cavity single-pass excitation.
Qualitative Analysis of Nanogram Samples with Fourier Transform Infrared Transmission Surface Electromagnetic Wave Spectroscopy
Authors: Nishikawa Yuji , Fujiwara Kunihiro , Shima Tetsuo
Published: June 2005

The intensity enhancement of infrared spectra with Ag island films in surface electromagnetic wave spectroscopy (SEWS), which is commonly associated with the ATR method, was observed with the use of an ordinary transmission configuration. We refer to this as “transmission SEWS” or “T-SEWS.” With 10 nm Ag, the magnitude of enhancement factor was about 200 for the NO2 symmetric stretching band at 1350 cm−1 with p-nitrobenzoic acid. In order to estimate its effectiveness as a qualitative analytical method, T-SEWS spectra were compared with normal transmission spectra with the use of several samples. The results showed that T-SEWS is useful in detecting and identifying nanogram amounts of substances which do not have reactive functional groups—e.g., triphenyl phosphate (TPP) or polydimethylsiloxane (PDMS), which do not have -COOH, -SO3H, -C=S, etc. A usable spectrum was observed from as little as 25 ng/cm2 of TPP with the use of a standard triglycine sulfate detector without a beam condenser. Combined with microspectroscopy, T-SEWS shows promise for picogram order analysis and chromatographic applications.
Characterization of a Helium/Argon Mixed-Gas Plasma for the Detection of Iodine by Inductively Coupled Plasma Optical Emission Spectroscopy
Authors: Sheppard Brenda S. , Caruso Joseph A. , Wolnik Karen A. , Fricke Fred L.
Published: June 2005

A He/Ar mixed-gas plasma has been investigated as an optical emission source for the determination of iodine at 2063 Angstroms. The effects of adding varying amounts of He to an argon plasma were studied. Optimal conditions were found with a total plasma composition of 34% helium. The auxiliary gas was 100% argon, whereas the carrier gas and the coolant gas were composed of 88% and 35% He, respectively. The mixed-gas plasma reduced the detection limit for iodine to 0.4 ppm, a sevenfold improvement over the detection limit obtained with a 100% Ar plasma. At the optimum conditions for iodine, detection limits for most other elements studied improved or stayed the same.
Application of a New Method of High-Resolution Spectral Analysis, “Sompi,” for Free Induction Decay of Nuclear Magnetic Resonance
Authors: Matsuura Toshio , Imanishi Yuichi , Imanari Mamoru , Kumazawa Mineo
Published: June 2005

A new spectral analysis method, “Sompi,” proposed for seismogram analysis based on the autoregressive (AR) model is shown to be useful in extracting unbiased NMR spectra with high resolution and high sensitivity from FID data. The Sompi method deconvolutes the given time series data into a set of spectral lines characterized by frequency, decay constant, initial amplitude, and initial phase. In order to determine the number of spectral lines in the AR modeling of FID data, the Akaike information criterion (AIC) is extended to the model with two parameters: an AR order which specifies the number of the candidate spectral lines, and the number of spectral lines with finite power that exist. The use of the Sompi method combined with the two-parameter AIC is shown to give an accurate and reliable spectrum by analyzing the synthetic data with white noise superimposed. The spectral resolution by the Sompi method is shown to be improved further by means of an intentional aliasing of narrow-band filtered data. The present method is demonstrated by analyzing the observed NMR data on Polyvinylchloride to resolve fine structure which cannot be recognized by FFT.
Determination of the Local Temperature at a Sample during Raman Experiments Using Stokes and Anti-Stokes Raman Bands
Authors: Kip Bert J. , Meier Robert J.
Published: June 2005

Sample heating due to high incident laser power in Raman experiments on (industrial) polymers and catalysts can easily lead to unwanted changes in morphology or desorption of surface species. Therefore temperature of the sample at the laser spot was studied by determining Stokes and anti-Stokes Raman intensities. Temperature can normally be determined within an accuracy of about 5 K, although for samples having nothing but Raman bands above 1000 cm−1, the anti-Stokes lines are very weak and accuracy of temperature determination decreased drastically. For most of the samples studied in the macro-Raman setup, powers up to 250 m\V could be used without measurable heating. In the micro-Raman setup heating started earlier due to higher focusing.
Fourier Transform Near-Infrared Attenuated Total Reflectance Spectroscopy of Silane Coupling Agents on Glass IRE
Authors: Nishio Etsuo , Ikuta Nobuo , Okabayashi Hirofumi , Hannah Robert W.
Published: June 2005

Attenuated total reflectance (ATR) has been shown to be highly sensitive for surface analysis. The major advantage of ATR is that the region of the specimen is restricted to a thin layer adjacent to the internal reflectance element (IRE). In an investigation of the surface reactions and interfacial effect of silane coupling agents on the surface of glass, a glass IRE was used in the near-infrared region (7000–4000 cm−1). This technique is useful for analyzing the near-surface of the glass IRE. By a comparison between each measured ATR spectrum and the transmission spectrum of the same glass IRE, it is possible to determine the mechanism of reaction of the silane coupling agent on the glass substrate. The process of dehydration was also investigated by calibration, with the use of the intensity of the band due to Si-OH groups. A condensation reaction occurs between molecules of the silane coupling agent in the bulk film. However, a small fraction of the agent reacts with the Si-OH groups of the glass at a lower rate. In this study, we show the transmission and ATR spectra of silane coupling agent reacted on a glass plate used for the IRE in the ATR method. With the use of the ATR method, the state of the dehydration condensation reaction, which involves hydrolyzing Si-OH at the surface, can be observed. Furthermore, the process of dehydration condensation reaction on the substrate of glass can also be compared with the bulk reactions measured by transmission.
Trace Determination of Cd, Cu, Br, and Cl with Electrothermal Vaporization into a Helium Microwave-Induced Plasma
Authors: Wu Mingin , Carnahan Jon W.
Published: June 2005

An electrothermal vaporization (ETV) system was used to introduce aqueous samples into a helium microwave-induced plasma (He-MIP). The plasma was operated at 2.45 GHz and 500 W. The sample introduction system consisted of a carbon-cup-type electrothermal vaporizer in a glass chamber. A vapor restriction device was used to enhance the efficiency of sample transport to the plasma. For obtaining the best detection limits, matrix modifiers were used for the nonmetals. Lead nitrate as a matrix modifier was found to be particularly efficacious for the determination of bromide and chloride. Detection limits with the ETV-He-MIP with 15-ML samples were: Cd, 10 pg (0.6 ppb) at 228.8 nm; Cu, 30 pg (2 ppb) at 327.4 nm; Br, 300 pg (20 ppb) at 470.5 nm; and Cl, 120 pg (8 ppb) at 479.5 nm. Although the detection limits for the two metals studied are greater than those that have been obtained by ETV-ICP-AES, the detection limits for Br and Cl are the best that have been obtained by an ETV-AES technique to date in the UV-VIS spectral region. Linear responses of analytes were obtained for each element. Matrix effects of selected metals and nonmetals on chloride were investigated and found to be insignificant.
Production of N2(A3Σu+) in the Low-Pressure Dielectric-Barrier (Ozonizer) Discharge
Authors: Cummings William P. , Piper Lawrence G.
Published: June 2005

Several reports in the literature imply that extremely large number densities of metastable nitrogen molecules may be found in the effluents of dielectric-barrier (ozonizer) discharges in flowing nitrogen. We have constructed a dielectric-barrier discharge which operates at 1 to 10 kV in flowing nitrogen or nitrogen mixtures with either argon or helium at total pressures between 0.3 and 6 Torr. Spectroscopic observations in the afterglow of this discharge indicate that virtually all observed excitation between 200 and 850 nm results from discharge streamers. All emissions are quenched upon adding a grounded loop downstream from the discharge. The absence of NO gamma-band emission when NO is added downstream from the grounded loop indicates that N2( A) number densities in the afterglow are below 105 molecules cm−3, some ten orders of magnitude below previous estimates.
Two-Dimensional Infrared (2D IR) Spectroscopy: Theory and Applications
Authors: Noda Isao
Published: June 2005

A novel concept in vibrational spectroscopy called two-dimensional infrared (2D IR) spectroscopy is described. In 2D IR, a spectrum defined by two independent wavenumbers is generated by a cross-correlation analysis of dynamic fluctuations of IR signals induced by an external perturbation. 2D IR spectra are especially suited for elucidating various chemical interactions among functional groups. Notable features of the 2D IR approach are: simplification of complex spectra consisting of many overlapped peaks; enhancement of spectral resolution by spreading peaks over the second dimension; and establishment of unambiguous assignments through correlation analysis of bands selectively coupled by various interaction mechanisms. The procedure for generating 2D IR correlation spectra and the properties of the 2D spectra are discussed in detail. Examples of 2D IR spectra are presented for atactic polystyrene and the proteinacious component of human stratum corneum to demonstrate the utility of this technique.
Evaluation of a Cooled Recirculating Nebulizer for Inductively Coupled Plasma Spectrometry
Authors: Olson L. K. , Caruso J. A. , Creed J. T. , Wolnik K. A. , Fricke F. L.
Published: June 2005

A recirculating nebulizer was constructed with the use of standard spray chambers and nebulizers and can be used in both a recirculating and normal solution nebulization mode. The use of a jacketed cooled spray chamber reduces a concentration effect to less than a 2% increase over a 30-min period. Washout times were improved by eliminating memory sources and also by using a cooled mini spray chamber. This recirculating system is compatible with isotope ratio and isotope dilution analysis of small-volume samples. Good agreement was obtained between certified and experimental values for Pb in two standard reference materials.
A Precise Measurement of the Cesium Spin-Exchange Relaxation Cross Section
Authors: Vallés J. A. , Tornos J.
Published: June 2005

A measurement of the Cs spin-exchange cross section ( σex = 1.40 ± 0.10 × 10−14 cm2) is presented. It is a result of an experiment on the hyperfine relaxation of an optically pumped cesium vapor in the presence of nitrogen buffer gas in experimental conditions which ensure the absence of quadrupole contributions and the minimizing of the influence of high diffusion orders on the relaxation signals.
Computer Modeling as an Aid to the Analysis of Kinetic Data
Authors: Mounfield W. Pratt , Stone Daniel A.
Published: June 2005

In studies of the eventual fate of toxic chemicals in the environment, it is common to acquire data on the concentration of chemical species of interest as a function of time. A mechanism is often postulated to explain the observed data. To test the proposed mechanism, one must cast the individual reaction steps into differential equations and integrate. In general, the proposed kinetic processes are nonlinear, and no closed analytical expressions are available. Thus, the only way to fit the observed data is to use numerical integration techniques. This paper describes the development of a computer program based on a modified Marquardt algorithm in conjunction with a least-squares differential corrector to estimate the required states and parameters. Actual data from the decay of hydrazine vapor in an environmental chamber are used to test four proposed loss mechanisms. The use of error residuals as a test of the model fit is demonstrated. The importance of sampling time regularity and integration step size is also shown.
The Development of a Spectral Data Base for the Identification of Fibers by Infrared Microscopy
Authors: Tungol Mary W. , Bartick Edward G. , Montaser Akbar
Published: June 2005

A detailed study of the application of infrared (IR) microscopy for single fiber analysis has been initiated. Spectra of single synthetic fibers were obtained rapidly and reproducibly with minimal sample preparation. Minor spectral variations, caused by deformation of the fibers during sample preparation, were observed between samples. These spectral variations were never sufficient to prevent the identification of the polymeric materials. An IR spectral library of 43 polymer fibers, which were distinguishable by their IR spectra, was constructed. The chemical subclass of unknown fibers, with the exception of acetates and nylons, could be accurately identified by a computer search using an absolute derivative difference searching algorithm.
Near-Infrared Spectroscopic Analyses of Poly(Ether Urethane Urea) Block Copolymers. Part II: Phase Separation
Authors: Miller Charles E. , Edelman Peter G. , Ratner Buddy D. , Eichinger Bruce E.
Published: June 2005

Second-overtone carbonyl bands at 1918 and 2036 nm in the near-infrared (NIR) spectrum are used to monitor the phase separation of poly(ether urethane urea) (PEUU) block copolymers at 100°C. Exact positions of urea and urethane carbonyl bands are determined by NIR spectroscopic analyses of model compounds in bulk and in dilute solution. Results indicate that the carbonyl groups in the copolymers are affected by two different structural processes that occur with annealing. A faster process causes an increase in the number of free urethane groups, and a slower process causes a decrease in the number of free urea and urethane carbonyl groups. Although several structural mechanisms can be used to describe these trends, more information is necessary to identify exact structural changes that occur with annealing.
Infrared Group Frequency Assignments Aided by Solvent Studies
Authors: Nyquist Richard A.
Published: June 2005

The antisymmetric NO2 or SO2 stretching modes or the out-of-phase N(C=O)2 or O(C=O)2 stretching mode for phthalic anhydride can be readily distinguished from their corresponding symmetric stretching mode or the in-phase stretching mode by recording infrared spectra of these compounds in CHCl3 and CCl4 solutions. In all cases the antisymmetric stretching mode or the out-of-phase stretching mode exhibits a significant decrease in frequency in CHCl3 solution, compared with its frequency in CCl4 solution, while the corresponding symmetric stretching mode or in-phase stretching mode either increases or decreases in frequency. When the symmetric or in-phase stretching frequency decreases, the decrease is significantly less than that exhibited by the antisymmetric stretching mode or the out-of-phase stretching mode in the same two solvents. The acceptor number (AN) values do not correlate with NO2 stretching frequencies.
Correction Procedures for Rare Earth Element Analyses in Inductively Coupled Plasma-Mass Spectrometry
Authors: Vaughan M. A. , Horlick Gary
Published: June 2005

The analysis of the rare earth elements by inductively coupled plasmamass spectrometry is complicated by spectral overlap problems involving M+, MO*, and MOH+ ions. Two correction schemes are compared in this study. One correction scheme is the classical algebraic approach (Gauss elimination) and the other is a method based on principal components analysis, also known as factor analysis. Both schemes work well, but the principal components analysis approach is considerably more flexible, is easier to expand to more elements, and can tolerate missing data.
Infrared and Raman Spectra of Trimesonitrile-14N3 and Trimesonitrile-15N3
Authors: Arenas J. F. , Marcos J. I. , Montañez M. A. , Ramirez F. J.
Published: June 2005

Trimesonitrile-14N3 and trimesonitrile-15N3 containing 99% nitrogen-15 were synthesized and their IR and Raman spectra recorded, both in solid phase and dissolved. The data obtained were used to assign the vibrational spectra of the two molecules on the basis of a D3 h symmetry. We also used the MINDO/3 and AM1 methods to calculate a semi-empirical force field for both compounds after optimizing their molecular geometry by each method.
Measurements of Fluorescence Heterogeneity in Human Teeth Using Polarization Microfluorometry
Authors: Araki Tsutomu , Miyazaki Eiichi , Kawata Terushige , Miyata Kazuyoshi
Published: June 2005

Human teeth fluoresce as a result of illumination by UV-light (λmax = 450 nm). The spectral, anisotropic, and temporal heterogeneities of a tooth's fluorescence have been investigated with respect to tooth structure. A polarization microfluorometer and a time-resolved fluorometer were employed. The fluorescence intensity of the dentin increases with tooth age. On the basis of the fluorometric investigations, it appears that a complex of cross-linked collagen with hydroxyapatite is a possible fluorescing compound within the tooth tissue. Observed fluorescence anisotropy in the tooth tissue suggests heterogeneous structure of the fluorescing compound. Anisotropy distribution shows characteristic profiles which are independent of age and sex, and of type of tooth. Analysis of fluorescence decay curves suggests that such profiles are due to the characteristic arrangement of the fluorophore electric dipole, which in turn relates to tissue construction.
Thermal Decomposition of Energetic Materials 37. SMATCH/FT-IR (

S

imultaneous

MA

ss and

T

emperature

CH

ange/FT-IR) Spectroscopy
Authors: Timken M. D. , Chen J. K. , Brill T. B.
Published: June 2005

A description is given of the design and operation of a new infrared spectroscopy sampling technique that permits real-time, Simultaneous MAss and Temperature CHange (SMATCH)/FT-IR measurements to be made on samples heated at high rates (up to 320°C/s) to about 600°C. The technique is illustrated with 13.4%N nitrocellulose.
Near-Infrared Spectroscopic Analyses of Poly(Ether Urethane Urea) Block Copolymers. Part I: Bulk Composition
Authors: Miller Charles E. , Edelman Peter G. , Ratner Buddy D.
Published: June 2005

The ability of near-infrared (NIR) diffuse reflectance spectroscopy to perform rapid bulk composition analyses of poly(ether urethane urea) (PEUU) block copolymers is demonstrated. Six polymer samples with known elemental compositions were used to construct calibration models using the method of classical least-squares (CLS). Results indicate that NIR diffuse reflectance spectroscopy can determine hard-segment and soft-segment contents of the bulk polymers within 2.6% mass over a range of 31% mass. Errors in the calibrations were caused by nonrepresentative NIR sampling of the polymers and by the presence of side products in the polymers. NIR spectra of model hard- and soft-segment materials are used to assign NIR bands to specific functional groups in the polymers.
Surface-Enhanced Raman Spectra of Eye Lens Pigments
Authors: Nie Shuming , Castillo Carolina G. , Bergbauer Katrina L. , Kuck John F. R. , Nabiev Igor R. , Yu Nai-Teng
Published: June 2005

Surface-enhanced Raman spectroscopy (SERS) has been applied to study lenticular pigments that are present in the eyes of certain diurnally active animals. Using Ag hydrosols pre-aggregated with NaClO4, we have obtained SERS spectra from dilute solutions of various model pigment compounds, including kynurenine, N-formylkynurenine, 3-hydroxykynurenine, β-carboline, bityrosine, anthranilic acid, 3-hydroxyanthranilic acid, and oxindole. The results obtained from these model compounds show that SERS is a particularly sensitive technique for the identification of lens pigments. We also report a procedure that enables high-quality SERS data to be obtained for the yellow pigments in the lens homogenates of grey squirrels, ground squirrels, and chipmunks. The surface Raman results confirm the identity of the low-molecular-weight, water-soluble pigment in the grey squirrel lens as a derivative of 3-hydroxykynurenine, but reveal that lens pigmentation in ground squirrels and chipmunks involves new chromophores. The significance of this finding in relation to the metabolic/photochemical generation of lens pigments is discussed.
Optogalvanic Detection of Laser-Desorbed Silver in a Low-Pressure Argon Atmosphere
Authors: Monts David L. , Su Meng-Chih
Published: June 2005

We report the first detailed investigation of laser-desorbed material probed by laser optogalvanic spectroscopy. When Ar transitions in the 555-575 nm region are excited, the laser-desorbed silver optogalvanic effect (OGE) temporal signal appears as a shoulder on the Ar OGE peak. Our studies show that the shoulder is due to Penning ionization of laser-desorbed Ag by Ar in highly excited states (15.12–15.51 eV). The temporal dependence of the laser desorption process was investigated. It was found that most of the sample was desorbed within, at most, 1200 laser pulses (2 min). A crude estimate of the absolute detection limit obtained here is tens to hundreds of nanograms; use of a dedicated, custom apparatus rather than the commercial, shielded hollow cathode lamp used in this study should permit confirmation of and improvement on this detection limit. The presence of a low-pressure argon atmosphere and the use of moderate laser power density may be crucial for successful application of this technique.
Sampling an RF-Powered Glow Discharge Source with a Double Quadrupole Mass Spectrometer
Authors: Duckworth Douglas C. , Marcus R. Kenneth
Published: June 2005

A double quadrupole mass spectrometer has been assembled to perform collision-induced dissociation (CID) of molecular ions sampled from a radio-frequency (rf) powered glow discharge atomization/ionization source. Low-energy ( Elab = 20 and 40 eV) collisions with argon target atoms efficiently dissociate species of the form M2+, MAr+, MO+, and Ar2+, and residual gas species. Exemplary CID mass spectra illustrate the enhanced reduction of potential molecular isobars relative to scattering losses of analyte (atomic) ions.
Spectral Modeling of Sulfonephthalein Indicators: Application to pH Measurements Using Multiple Indicators
Authors: King D. Whitney , Kester Dana R.
Published: June 2005

The visible spectra of five sulfonephthalein indicators (thymol blue, bromophenol blue, bromocresol green, bromocresol purple, and phenol red) were deconvoluted into four Gaussian components. The spectra of the basic form of the indicator were described by three components and the acidic form by one component. The combination of the spectral model, pH, and pK data allowed quantative prediction of indicator spectra as a function of pH. A general equation was derived for the calculation of pH from two absorbance measurements of a solution which contains one or more indicators. The application of multiple indicators significantly expands the pH range over which pH measurements can be made. With the use of the modeled spectra for several indicators, optimal indicator combinations and measurement wavelengths for specific pH ranges were determined. The combination of phenol red and bromocresol green allowed determination of seawater pH over the range 3.0 to 8.2, which is suitable for oceanic pH and alkalinity determinations.
Evidence for a common regulation in the activation of a polyphenol oxidase by trypsin and sodium dodecyl sulfate
Authors: Gandía-Herrero Fernando , Jiménez-Atiénzar Mercedes , Cabanes Juana , García-Carmona Francisco , Escribano Josefa
Published: June 2005

Polyphenol oxidase (PPO) was extracted from beet root, in both soluble and membrane fractions, and in both cases the enzyme was in a latent state. PPO from the membrane fraction showed no diphenolase activity unless it was activated by trypsin or sodium dodecyl sulfate (SDS). The kinetics of the activation process of latent PPO by trypsin was studied and the specific rate constant of active PPO formation,k3, showed a value of 0.03 s−1. The protease-activated form showed a pH optimum (6.5) and kinetic properties identical to those of the SDS-activated enzyme. Evidence is provided for the existence of a common peptide responsible for the regulation of the activity of the enzyme by both proteolysis and SDS detergent. Formation of the active proteolyzate was followed by spectroscopic measurements, Western blotting and partially denaturing SDS-PAGE.