bluuebunny/crossref_metadata_2025 huggingface dataset:
MAGIC-LC/FT-IR Spectrometry with Buffered Solvent Systems
Authors: Robertson R. M. , de Haseth J. A. , Browner R. F.
Published: June 2005

The first demonstration of identifiable infrared (IR) spectra obtained from buffered (volatile and nonvolatile buffers) mobile phases using the Monodisperse Aerosol Generator Interface for Combining Liquid Chromatography with Fourier Transform Infrared (MAGIC-LC/FT-IR) spectrometry is described. Ammonium acetate, a volatile buffer, was used to buffer an 80:20 acetonitrile: water mobile phase to pH 5.0. Caffeine was deposited from this buffered mobile phase, and the spectrum was used as a reference to compare with caffeine spectra obtained from nonvolatile buffered mobile phases. The two nonvolatile buffers used were potassium hydrogen phthalate (KHP) and potassium dihydrogen phosphate (KH2PO4). The KH2PO4 was used to buffer an acetonitrile:water mobile phase and a methanol:water mobile phase, whereas the KHP buffer was used only in a methanoh:water mobile phase. Samples of caffeine were deposited from each of the above buffer systems along with the nonvolatile buffer. Infrared spectra of caffeine were obtained by spectral subtraction of previously stored buffer spectra from the caffeine:buffer spectra. The resulting spectra were identical to a caffeine reference spectrum.
Absolute Quantum Yields for Exciplex Fluorescence
Authors: Hale S. J. , Melton L. A.
Published: June 2005

The absolute quantum yields for exciplex fluorescence in four solutions which have potential as exciplex-based vapor/liquid visualization systems have been measured. The room-temperature absolute quantum yields for 10% dibutyl-aniline/0.4%, 1-cyanonaphthalene, 12.5% 1-methyl-naphthalene/0.5% N,N,N′,N′-tetramethyl- p-phenylenediamine (TMPD), 10% trihexylamine/1.0% 1-cyanonaphthalene, and 10% naphthalene/1.0% TMPD in hexadecane or cyclohexane are 0.03 ± 0.005, 0.05 ± 0.002 (308 nm), 0.02 ± 0.001, and 0.16 ± 0.021, respectively. The temperature dependence of the absolute quantum yield for the 10% naphthalene/1% TMPD in the hexadecane system was measured over the range of 23 to 260°C and was found to decrease by 20–30% at 260°C.
Hexachlorodibenzo-p-Dioxin Isomer Differentiation by Capillary Gas Chromatography Fourier Transform Infrared Spectroscopy
Authors: Grainger James , Reddy V. Vikram , Patterson Donald G.
Published: June 2005

Vapor-phase infrared spectra of the 10 hexachlorodibenzo- p-dioxin isomers were recorded at low microgram concentrations. A unique infrared spectrum was observed for each chromatographically separated or spectrally subtracted mixture component. The structures for individual isomers in each isomer pair were assigned by qualitative valence bond evaluations and empirically derived quantitative estimations of ether linkage asymmetric stretching frequencies and by correlations with characteristic aromatic skeletal stretching vibration patterns.
Diffuse Reflectance Infrared Spectroscopic Characterization of Silica Dehydroxylation
Authors: White Robert L. , Nair Aurobindo
Published: June 2005

Diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) is employed to study the dehydroxylation of amorphous silica. Dehydroxylation results in the appearance of infrared absorption bands at 1022, 1107, and 1240 cm−1 assigned to asymmetric stretching vibrations for three different siloxane bridge types. The 1107-cm−1 absorbance band represents a siloxane bridge that is indistinguishable from bulk species. The 1022-cm−1 absorbance band represents a siloxane bridge with a bond angle that is smaller than the bulk, with little change in the stretching vibration force constant. The 1240-cm−1 absorbance band derives from a siloxane bridge characterized by a stretching force constant significantly larger than that of bulk siloxane bridges. This band may be indicative of a highly strained or broken siloxane bridge.
Vibrational Spectroscopy of Phthalimides Adsorbed on Alumina: Models for Polyimide Adhesion
Authors: Ramsier R. D. , Henriksen P. N.
Published: June 2005

Vibrational spectra of phthalimide and N-phenylphthalimide adsorbed on oxidized Al substrates have been studied with the use of inelastic electron tunneling spectroscopy. Ring mode bands indicate that the substituted benzene rings interact strongly with the surface, thus adsorbing in a flatwise configuration. There is spectral evidence of Al-N complexing, and results also support the formation of weak Al-O=C bonding via one carboxyl group per molecule on average. No C=O bond cleavage has been observed, and the effect of surface OH groups on phthalimide adsorption remains unclear.
Component Selection for Fiber-Optic Fluorometry
Authors: Thompson Richard B. , Levine Michael , Kondracki Lynne
Published: June 2005

A wide variety of fiber-optic sensors based on fluorescence have been developed for important applications in the last few years. Unfortunately, no systematic study describing an optimized design has appeared. A fiber-optic fluorescence sensor testbed was constructed, and different optical designs and components were compared for sensitivity in detecting fluorescence. Different beamsplitters, launching objectives, filters, detectors, and configurations were evaluated on the basis of their measured signal-to-noise ratio in detecting 100 picomolar fluorescein. Sources of noise and background were identified, and generally applicable means for minimizing them are described.
Crossed Interferometric Dispersive Spectroscopy
Authors: Sweedler Jonathan V. , Jalkian Rafi D. , Sims Gary R. , Denton M. Bonner
Published: June 2005

A novel design is described which combines dispersive and interferometric spectrometric instrumentation for ultraviolet visible spectroscopy, offering significant advantages in comparison to conventional spectroscopic configurations. The optical system incorporates the triangular common-path interferometer with an additional cross-dispersive element, allowing spectra to be obtained in a format compatible with rectangular CTD array detectors. The use of a cross-dispersive optical element reduces the distributive multiplex effects of interferometry in a rugged, compact, optically simple system.
Comparison of Aerosol Sample Introduction Systems for a DCP
Authors: Rayson Gary D. , Chrisman Vanessa M.
Published: June 2005

The results of a comparative study of the relative analytical performance of different nebulizer and spray-chamber designs with a direct-current plasma (DCP) are described. Concentric-glass, cross-flow, and Babington-type nebulizers were each evaluated with either a double-pass or an open spray-chamber geometry for the effect of each combination on the observed linear dynamic range and the magnitude of interferences arising from the presence of an easily ionizable element (sodium) and difficult-to-vaporize species (phosphate salts). The performance of each of these combinations was compared to that of the nebulizer/spray-chamber configuration provided by the manufacturer. For nearly all cases, the manufacturer's configuration provided, at worst, comparable signal intensities for all conditions investigated.
A Magnetron DC Arc Plasma for Aerosol Analysis
Authors: Slinkman David , Sacks Richard
Published: June 2005

A direct-current arc device using coaxial electrodes and an external magnetic field is combined with a glass-frit nebulizer for the analysis of metallic elements in aqueous samples. The magnetic field is applied parallel to the electrode axis to produce a magnetron-type rotation of the arc current channel. The resulting plasma is diffuse and is more easily penetrated by the aerosol particles. The plasma is viewed normal to its axis at one end of the cylindrical electrode assembly. The intense continuum background from the current channel is masked by withdrawing the center electrode into the outer cylindrical electrode. The effects of electrode configuration and plasma current on analysis line-to-background ratios are described. Preliminary analytical data are presented for Cu, Mn, Mg, and Ca.
Absorbance Linearity and Repeatability in Cylindrical Internal Reflectance FT-IR Spectroscopy of Liquids
Authors: Doyle Walter M.
Published: June 2005

This paper reports the results of a program aimed at eliminating the sources of performance variability and excessive nonlinearity that have limited the effectiveness of the cylindrical internal reflectance technique for use in quantitative FT-IR analysis. After discussing the various optical factors that can affect performance, it describes a new adjustment-free optical design which promises to eliminate those factors which lead to data unpredictability. Finally, it summarizes the results of a series of experiments carried out to test the effectiveness of the new design. These confirm the achievement of three significant improvements: an enhancement of band strengths by factors of typically 2.5 to 3, significantly improved absorbance linearity, and a high degree of data repeatability under varied experimental conditions.
Investigation of Micellar Effects in Thermal Lens Spectrophotometry
Authors: Georges Joseph , Mermet Jean-Michel
Published: June 2005

The effect of micellar solutions in thermal lens spectrophotometry was investigated. Several aspects of the thermal lens signal including the formation rate and the relaxation of the thermal lens were compared in various neat solvents and in aqueous micellar solutions. The experiments were performed with a double-beam thermal lens apparatus based upon a pulsed-dye laser as the excitation beam and a He-Ne laser as the probe beam. The results show that, if micellar solutions can be used to solubilize hydrophilic species in solvents having better thermo-optical properties than water, they do not provide sensitive modifications of the thermo-optical properties of water. The absence of micellar effect in thermal lensing, in comparison to the well-known micellar enhanced fluorescence, is discussed with respect to the size of micelles and micellar dynamics, the photophysical processes associated with thermal lensing, and the time dependence of the thermal lens signal.
Evaluation of Current Nebulizers and Nebulizer Characterization Techniques
Authors: Smith Thomas R. , Denton M. Bonner
Published: June 2005

The operating characteristics of a number of recent, commercially available inductively coupled plasma (ICP) nebulizer designs have been compared. The operating characteristics studied included bulk efficiency, primary and tertiary aerosol production, and analyte response by ICP-AES. Several concentric glass nebulizers along with a slurry and a dual-platinum-grid nebulizer were investigated. In all cases, tertiary aerosol production was found to be the best indicator of the analytical performance of the nebulizer. Of the nebulizers studied, the dual-platinum-grid nebulizer was found to generate the largest quantity of aerosol and to possess the most compatible droplet-size distribution for use with an ICP.
Studies of Aerosols Generated by Electrically Vaporized Thin Films for ICP-AES
Authors: Brewer Stephen W. , Trivedi Ketan , Braid Frederick I. , Sacks Richard D.
Published: June 2005

Aerosols generated by the electrical vaporization of samples placed on thin silver films for subsequent introduction into an inductively coupled plasma have been examined. Of the silver ablated during electrical discharges, less than 10% is trapped on 0.1-micrometer pore-size filters placed at the end of the transfer tube. Much larger masses of carbonaceous particulate material, up to 0.25 mg, are introduced into the ICP torch, possibly accounting for intense time-dependent band and continuum emission. Scanning electron microscopy of trapped particles of exploded film material shows evidence of melting. Particles of Mn and VC collected after film vaporization also show evidence of size reduction. The higher boiling point of VC may account for low emission intensities observed when larger particles of this material are taken as samples.
The Characterization of High-Critical-Temperature Ceramic Superconductors by Vibrational Spectroscopy
Authors: Ferraro John R. , Maroni Victor A.
Published: June 2005

The high-Tc superconducting ceramics have been extensively investigated by Raman and infrared spectroscopy. Some of the k = 0 phonons of the La2– x M xCuO4( M = Sr, Ba), MBa2Cu3O7–δ, (MBCO), Bi-(Ca,Sr)-Cu-O, Tl-(Ba,Sr)-Ca-Cu-O, Pb-Sr- Ln-Ca-Cu-O, and Ba1– xK xBiO3 (BKB) systems have been observed, and assignments made. The Raman measurements on single crystals have provided the more enlightening results, inasmuch as assignments are facilitated by the use of polarization techniques. Assignments have also been aided by oxygen stoichiometry experiments, substitution of rare earth cations for Y3+ in YBa2Cu3O7–δ, low-temperature measurements, and isotopic studies. Infrared studies and assignments for the Bi, Tl, Pb, and BKB superconductors are lacking. Many of the zone-center phonons for each of the high-Tc materials (particularly those for non-totally-symmetric modes) remain undetected. Additionally, some disagreement in assignments (Raman and IR) persists, even for the more extensively studied La2– x M xCuO4 and MBCO superconductors.
Chemistry and Structure of Coals: Hydrogen Bonding Structures Evaluated by Diffuse Reflectance Infrared Spectroscopy
Authors: Fuller E. L. , Smyrl N. R.
Published: June 2005

Coal formation is a dynamic process that transforms plant residues into a rigid matrix of carbonaceous materials over the eons at somewhat elevated temperatures and pressure. Diffuse reflectance infrared spectroscopy (DRIS) is very informative in monitoring the maturation process by studying representative samples of given geologic maturity. Qualitative examination of the spectra is a facile and reliable means of ranking the coal. Further analyses of the DRIS data reveal that hydrogen bonding is a major force binding coals together. Five distinct types of hydrogen bonding exist, corresponding to the number of electron donor oxygen (proton acceptor) atoms involved. Rigidification of the cellulosic structures develops stronger fields, giving rise to a generally stronger set of hydrogen bonds. The successively stronger hydrogen bonds are noted to give rise to lower frequencies of resonance and widths of bands, and the stronger dipoles have greater extinction coefficients. Infrared spectroscopy is the most informative means of exploring the intricacies of the hydrogen bonds in coals. This preliminary work shows the merits of the DRIS technique, in that the studies are performed with neat samples (free from chemical and physical artifacts associated with support media and dilution agents).
Analysis of Deoxyribonucleotides with Principal Component and Partial Least-Squares Regression of UV Spectra after Fourier Preprocessing
Authors: Donahue Steven M. , Brown Chris W. , Scott Matthew J.
Published: June 2005

Principal component (PCR) and partial least-squares (PLS) regression with Fourier preprocessing of ultraviolet spectra have been evaluated for the analysis of mixtures of the four major nucleotides of DNA. Results have been compared with those obtained without Fourier preprocessing and with those obtained with a straightforward P-matrix approach with optimum wavelength selection. Calibrations were developed and tested with the use of sixteen standard and fourteen unknown mixtures. The standards and nine of the unknowns followed the typical base equivalences found in DNA. For these nine unknowns, the best average percent error in the Fourier domain was 0.61%, as compared to 0.65% in the spectral domain. The remaining five unknowns, in which the nucleotide concentrations were independent of each other, provided a particularly difficult test of each method's ability to distinguish the components. For these unknowns, the best errors in the Fourier and spectral domains were 1.20 and 1.85%, respectively. For assessment of the effect of protein, the analysis was repeated with varying amounts of albumin up to 36% by weight added to the mixtures. All of the full spectral methods (PCR and PLS in the spectral and Fourier domains) were able to compensate for the spectral interference of the added protein and produced results as good as those without the protein. For nucleotide mixtures, ultraviolet spectroscopy represents a rapid, economical, sensitive, and nondestructive alternative to existing techniques.
Infrared Study of Maleic Anhydride in Solvent Systems
Authors: Nyquist Richard A.
Published: June 2005

The out-of-phase (C=O)2 stretching mode for maleic anhydrides, vout-of-phase (C=O)2, is in Fermi resonance with a B1 combination tone, and the extent of Fermi resonance interaction can be altered drastically depending upon the particular solvent system used in the study. The vout-of-phase (C=O)2 and vin-phase (C=O)2 modes can be differentiated by solvent system studies, since the out-of-phase mode shifts more in frequency than the in-phase mode. Both v(C=O)2 modes decrease in frequency as the polarity of the solvent system increases or the amount of intermolecular hydrogen bonding increases, such as in the case of an increasing mole % concentration of chloroform.
Multiple Reagent Aminopeptidase Profiling of Bacteria
Authors: Azimi N. T. , Lytle F. E. , Huber D. M. , Whitaker J. E. , Haughland R. P.
Published: June 2005

A two-component, fluorometric procedure has been developed for aminopeptidase profiling of plant pathogens. The method utilizes the simultaneous incubation of bacteria in a combination of substrates, one tagged with β-naphthylamine and the other with 6-aminoquinoline. After incubation, emission from the resultant mixture is examined with the use of both spectral and temporal resolution. A matrix least-squares method based on concatenated decay data at two different wavelengths is suitable for separation for responses with the individual substrates in the mixture. This approach decreases the large number of solutions required for aminopeptidase profiling by a factor of two, while simultaneously minimizing interferences from the biological matrix.
Phase Plane Method for Room-Temperature Phosphorescence Lifetime Determination of Single and Double Exponential Decays
Authors: Rupérez A. , Ayala L. , Laserna J. J.
Published: June 2005

The phase plane (PP) method for evaluation of decay parameters is applied to the determination of room-temperature phosphorescence lifetimes on filter-paper substrates. The commonly used semilogarithmic (SML) method and the phase plane method are compared experimentally. The prominent advantage of the PP method is precision, which in most of the cases evaluated is about one order of magnitude better than that of the semilogarithmic method. The PP method is able to detect double exponential decays where the SML provides a single decay component, and it is not susceptible to the computational failures of the SML method in situations where a high background phosphorescence contribution is found. The PP method is more elaborate than the SML method, but it is computationally simple and is easy to program.
Functional Group Identification by Two-Dimensional 29Si NMR Spectroscopy with Reversed Detection and Signal Winnowing
Authors: Pelnař Jan , Blechta Vratislav , Schraml Jan
Published: June 2005

Trimethylsilylation followed by recording of 29Si NMR spectra is a useful method for functional group analysis, especially as the 29Si lines can be assigned to a particular group by exact experimental techniques. The low sensitivity of these techniques can be overcome by application of reversed methods employing 1H-detection. Adaptation of heteronuclear multiple quantum coherence 2D NMR spectroscopy to the measurements of 29Si-1H correlations is described, and preparatory experiments for winnowing signals of protons coupled to a 29Si nucleus are presented. The winnowing experiments designed to optimize 2D experiments have a wider application in identifying the signals of protons that are geminal to the functional group.
The Determination of Arsenic in Environmental Samples by Inductively Coupled Plasma-Atomic Emission Spectrometry with an in situ Nebulizer/Hydride Generator
Authors: Hwang J. David , Huxley Howard P. , Diomiguardi John P. , Vaughn Wilma J.
Published: June 2005

A simple and very inexpensive in situ nebulizer/hydride generator was used with ICP-AES for the determination of arsenic in environmental samples. The applications of hydride generation ICP-AES eliminated the spectral interference and sensitivity problem of arsenic determination encountered when conventional pneumatic nebulization was used for sample introduction. The key features of our study which distinguish it from previous works in this field are: (1) it greatly reduces the amount of time needed for sample preparation; (2) only a minimal and inexpensive modification of existing standard equipment is required; and (3) only a low-/medium-power plasma is required, in contrast to the high-power plasma required with other methods. This method has a detection limit of 1 ng/mL of the As 193.759-nm line and 2 ng/mL of the As 228.812-nm line, respectively. The linear calibration range is over 3 orders of magnitude, starting from the detection limit.
Laser Raman Spectral Determination of Zinc Halide Complexes in Aqueous Solutions as a Function of Temperature and Pressure
Authors: Marley N. A. , Gaffney J. S.
Published: June 2005

Laser Raman spectroscopy has been used to determine directly the aqueous-phase zinc chloride and bromide species in solution as a function of temperature and pressure. With the use of the bromide system as a model, and by adjustment of the chemical and physical conditions to promote changes in the chemical equilibrium, identification of the mono-, di-, tri-, and tetra-halo zinc complexes has been performed. The spectral band positions, the Raman scattering coefficients, and the relative concentrations of the complexes are reported. The temperature and pressure dependence on the relative concentrations of the complexes have been examined. For the zinc/halide aqueous systems, temperature has a much more pronounced effect upon the species distributions than does pressure.
Direct Analysis of Solid Powder Samples with Electrically Vaporized Thin-Film Sampling and ICP Detection
Authors: Trivedi Ketan M. , Brewer Stephen W. , Sacks Richard D.
Published: June 2005

Solid powder samples deposited on Ag thin films are electrically vaporized by capacitive discharge. The aerosol produced by this method is introduced into the ICP. A low-volume vaporization chamber has been designed for these experiments. A magnetic field of a few kG normal to the electric field in the thin-film plasma is used to improve the plasma/sample interaction. A continuous flow of Ar or 60%/40% Ar/O2 through the chamber carries the aerosol from the capacitive discharge plasma into the ICP. Analytical data will be presented for a number of NIST reference materials emphasizing the determination of Mn, V, and Ni in biological and refractory inorganic matrices.
FT-IR Metal Overlayer ATR Spectroscopy Using a Coated Elastomer Backing Material
Authors: Khoo C. G. L. , Ishida H.
Published: June 2005

A metal overlayer FT-IR-ATR technique that is found to substantially enhance the signal-to-noise ratio of monolayer and submonolayer film spectra is described. Experimental evidence of the enhancement is given for, as examples, a deposited polyvinyl acetate) film of 0.5 or 5 nm and a thin film of adsorbed protein human serum albumin, estimated to be of the order of 5 nm. The evidence is supported by simulations showing the expected trends in Δ R as a function of thickness of the air gap between the film sample and the metal overlayer, the thickness of the film sample itself, and electric field diagrams illustrating that polarization dependence and enhancement effects can result from a correct choice of optical configuration. The metals investigated include gold and aluminum. The practical aspects and limitations of this technique are also discussed.
An Automated Direct Sample Insertion System for Inductively Coupled Plasma-Atomic Emission Spectrometry
Authors: Chan W. T. , Horlick G.
Published: June 2005

An automated direct sample insertion device for inductively coupled plasma-atomic emission spectrometry is described. Graphite cup sample probes can be mechanically inserted into the plasma, and the insertion sequence is completely under computer control via a stepper motor. Multichannel high-speed electronics have been developed for a direct-reading polychromator that allow the real-time digitization of the transient spectral signals from up to six channels simultaneously. A small robot arm is used to automate exchange of the graphite cup sample probes. Custom software has been developed for system control and signal processing. For volatile elements such as Zn and Cd, detection limits are in the pg range for a 10 μL solution sample.
Determination of Crystallinity and Morphology of Fibrous and Bulk Poly(ethylene terephthalate) by Near-Infrared Diffuse Reflectance Spectroscopy
Authors: Miller Charles E. , Eichinger B. E.
Published: June 2005

Diffuse reflectance spectroscopy in the near-infrared (NIR) region (1100-2400 nm) was used to characterize the morphology of fibrous and bulk Polyethylene terephthalate) (PET). The method of Partial Least-Squares (PLS) was used to correlate NIR spectra of PET yarns with percent crystallinity. Standard error of prediction values for percent crystallinity in PET yarns are in the range of 2–3.5% crystallinity, and depended on the specific NIR spectral region used for analysis. Principal Components Analysis (PCA) was used to study the differences in NIR spectra of bulk PET samples that were crystallized at different temperatures. It was observed that NIR spectroscopy can detect changes in both intermolecular and intramolecular interactions in PET. The observed effect of crystallization temperature on the morphology of bulk PET is very similar to effects observed in earlier IR and thermal analyses. In addition, detection of moisture in bulk PET is demonstrated.
Corrected Performance of SIT Vidicons Exposed to Transient Radiation
Authors: Uchida Teruo , Itoh Seiji , Coleman David M. , Minami Shigeo
Published: June 2005

The SIT vidicon detector has many features which would indicate utility as a detector for time-resolved spectroscopy. Unfortunately, the problem of capacitive lag, under pulsed detection modes, can lead to highly erroneous spectroscopic intensities and linewidths. We have theoretically modeled the capacitive lag characteristics of the SIT vidicon and have developed a mathematical “correction factor” which can result in greatly enhanced performance. Results will be described for pulsed-LED test sources. Application to a variety of transient discharges appears possible.
Infrared Studies of Ketones: Parameters Affecting the Induced Carbonyl Stretching Vibration by Solute/Solvent Interaction
Authors: Nyquist Richard A.
Published: June 2005

The carbonyl stretching frequency, vC=O, decreases as the polarity of the solvent increases. The vC=O frequencies for dialkyl ketones are affected by intermolecular hydrogen bonding of the solvent proton with the free pair of electrons on the carbonyl oxygen atom. The strength of the intermolecular hydrogen bond is determined by steric effects of both the solvent and solute, the acidity of the intermolecular hydrogen bond proton, and the basicity of the ketone carbonyl group.
Aggregation and Matrix Effects on the Infrared Spectrum of Microcrystalline Powders
Authors: Iglesias J. E. , Ocaña M. , Serna C. J.
Published: June 2005

Two pure phonon theories have been used for the interpretation of the infrared absorption spectra of powdered solids: the theory of absorption and scattering of light by small particles (TAS) and the theory of the average dielectric constant (TADC). The comparison between both theories shows that they are equivalent for particle sizes smaller than 2 μm and low particle concentration. However, when the particle concentration is significant, only TADC can be used to analyze the experimental spectra, thus obtaining a qualitative estimation of particle aggregation in a powder. Matrix effects were also observed in the experimental powder spectra, which can be accounted for by TADC.
Use of Absorption Spectra to Determine Crystal Structure in f-Transition Element Compounds
Authors: Peterson J. R. , Young J. P. , Wilmarth W. R. , Haire R. G.
Published: June 2005

It has been determined that various similarities of some f- f absorption peaks observed in the spectra of f-transition element compounds can be used to elucidate the crystal structure of a given compound. Examples of this interpretation of spectra are presented along with some limitations of the technique. One application of this process leads to further verification of the AlCl3-type monoclinic structure of EsBr3.
Doubled Multiplexing in Fourier Transform Raman Spectroscopy
Authors: Radziszewski Juliusz G. , Michl Josef
Published: June 2005

The use of a Chevron filter for the rejection of light at the 1064-nm excitation wavelength permits the simultaneous detection of Stokes and anti-Stokes Raman lines (doubled multiplexing). This enhances spectrometry and photometric accuracy and permits a measurement of the true vibrational temperature of the sample. Down to Raman shifts as low as 40 cm−1, near-IR Raman spectra recorded on an optimized Nicolet SXR 60 instrument are distinctly superior to previously reported spectra of similar samples recorded on FT or, more slowly, on dispersive instruments.
Temperature Measurement in a CO2 Laser Beam by Laser-Induced Fluorescence of O2
Authors: Lalo C. , Masanet J. , Deson J. , Ben-Aim R. , Rostas J.
Published: June 2005

A mixture of SF6-O2 is irradiated by an infrared (10.6 μm) cw CO2 laser. Absorption by SF6, and subsequent collisional energy transfer, heats the mixture. Vibrationally excited ground-state O2 is detected at levels v = 0, 1, and 2 by laser-induced fluorescence in the B3 Σu− X3Σ8− – Schumann-Runge system with an ArF laser (193.3 nm). Comparison of the observed LIF spectrum with spectra simulated at various temperatures shows that the molecular oxygen in the IR laser beam is thermalized at a temperature of about 700 K.
Quantitative Analysis of Cellulosic Fillers Using Infrared Reflectance Spectroscopy
Authors: Kalasinsky Kathryn S. , Lightsey George R. , Short Paul H. , Durig James R.
Published: June 2005

For production of a cellulosic filler that is compatible with thermoplastic polymers, a primarily nonpolar or lignin surface is needed. In order to allow quantitative measurement of the cellulose-to-lignin ratio on the surface of the fillers, infrared reflectance techniques and computer curve-fitting were employed. By the use of this method of analysis, relative quantitation was obtained, and it was possible to determine that careful control of certain parameters during the production of thermomechanical pulps produced a more nonpolar lignin-like surface that was compatible with the thermoplastic polymers.
Solvent-Induced Carbonyl Frequency Shifts: Cyclopentanone and Cyclohexanone
Authors: Nyquist Richard A.
Published: June 2005

The carbonyl stretching vibration, vC=O, for cyclopentanone is in Fermi resonance with a combination tone, and the amount of Fermi resonance interaction between these two modes is dependent upon the amount of solute/solvent interaction. Correction for Fermi resonance shows that vC=O for cyclopentanone decreases in frequency by approximately 17.1 cm−1, progressing in the series of solvents from hexane through methyl alcohol. In the same series of solvents the vC=O frequency for cyclohexanone decreases in frequency by approximately 22 cm−1, progressing through the series of solvents hexane through methyl alcohol. Moreover, the vC=O mode for cyclohexanone occurs at a lower frequency than the vC=O mode for cyclopentanone (after correction for Fermi resonance) by between 26.5 and 33.2 cm−1, depending upon which particular solvent was used to dissolve cyclopentanone and cyclohexanone. The larger decrease in frequency for vC=O of cyclohexanone compared to vC=O for cyclopentanone in the same series of solvents is attributed to the fact that the (CH2)5 group contributes more electrons to the C=O group than does the (CH2)4 group. Consequently, the carbonyl group for cyclohexanone is more basic than the carbonyl group for cyclopentanone. Thus, there is a larger solute/solvent interaction in the case of cyclohexanone than in the case of cyclopentanone. The solvent acceptor numbers do not correlate well with the vC=O frequencies for either cyclohexanone or cyclopentanone (ACFFR).
A Tungsten Filament Vaporizer for Sample Introduction into a Direct-Current Plasma
Authors: Buckley Brian T. , Boss Charles B.
Published: June 2005

The interface of a tungsten filament vaporization source with a direct-current plasma has produced significant improvement over other electrothermal vaporization plasma emission sources. A unique means of filament heating, using microprocessor control, is introduced. This allows temperature programming and the synchronization of the vaporization and data collection processes necessary to capture the transient analyte signals. The small dead volume, short interface distance, and rapid heating rates all contribute to the very narrow and rapidly appearing emission profiles. The mass detection limits are 80 fg Ca, 200 fg Cu, 90 fg Fe, and 200 fg Fe. These are among the lowest detection limits reported for thermal vaporization-plasma emission techniques. The copper concentration was determined in whole swine blood.
A Versatile Analytical Method of Identifying Adhesive on Stamps by Specular-Reflectance Fourier Transform Infrared Spectroscopy
Authors: Wang Jin Hai
Published: June 2005

A specular-reflectance FT-IR spectroscopic technique has been applied to analyze the adhesives on stamps. The results show that it is better than the reported diffuse-reflectance technique, particularly in the suitability of sample size. The spectra of some used and unused stamps from several different countries were obtained; some exhibited apparent differences and some looked basically identical. The spectra of glues on the edge papers of stamps show the promising potential applications of this technique for other adhesive analysis of documents and books.
Polycyclic Aromatic Hydrocarbon Solute Probes. Part VII: Evaluation of Additional Coronene Derivatives as Possible Solvent Polarity Probe Molecules
Authors: Acree William E. , Tucker Sheryl A. , Zvaigzne Anita I. , Street Kenneth W. , Fetzer John C. , Grutzmacher Hans-Fr.
Published: June 2005

Fluorescence emission spectra are reported for dinaphtho[8,1,2abc; 2′,1′,8′klm]coronene, naphtho[8,1,2abc]coronene, naphth[2′,1′,8′,7′: 4,10,5]anthra[1,9,8abcd]coronene, dibenzo[bc,ef]coronene, benzo[1,2,3bc;4,5,6b′c′]dicoronene, anthra[2,3a]coronene, dinaphtho-[8,1,2abc;2′,1′,8′jkl]Coronene, and tetrabenzo[de,hi,mn,qr]naphthacene dissolved in n-hexadecane, butyl acetate, dichloromethane, and acetonitrile. Results of these measurements are used to screen PAHs for potential solvent polarity probe behavior. Of the eight PAHs studied, only naphtho[8,1,2abc]coronene, dinaphtho[8,1,2abc;2′,1′,8′klm]-coronene, and anthra[2,3a]coronene were classified as probe molecules. The fluorescence spectra of the first two PAHs show selective enhancement of the I band emission intensity in polar solvents. For anthra-[2,3a]coronene, the measured ratio of emission intensities of bands I and II decreased systematically with increasing solvent polarity.
An Analysis of Modulation Experiments for Raman Optical Activity
Authors: Hecht L. , Barron L. D.
Published: June 2005

The dependence of Raman optical activity and the associated artifacts on the scattering angle is discussed in terms of the Stokes-Mueller calculus for the modulation between right and left circular polarization states in the incident laser radiation, in the Raman scattered light, and in both simultaneously. The incident beam modulation technique implemented in backward scattering is identified as the ultimate experimental strategy for measurements on chiral molecules randomly oriented in an optically isotropic phase. Both the incident and the scattered beam modulation techniques have been found to isolate the pure magnetic dipole contribution to the circular intensity differences in right-angle scattering for orientations of the analyzer in the scattered beam and of the azimuth of the linearly polarized incident radiation, respectively, at ∼ ± 35.26° from the vertical.
Instrumentation for Steady-State and Dynamic Fluorescence and Absorbance Studies in Supercritical Media
Authors: Betts Thomas A. , Bright Frank V.
Published: June 2005

We describe and characterize a new instrument for the measurement of: (1) steady-state excitation, emission, and absorbance spectra; (2) fluorescence lifetimes; and (3) phase-resolved fluorescence spectra in supercritical fluid media. Time resolution is on the order 10–20 ps, spectral resolution is 1 nm from 225–700 nm, and pressure and temperature can be controlled accurately and safely from 1 to 300 ± 0.7 atm and 273.2 to 373.2 ± 0.1 K, respectively. The instrument shows great promise for the elucidation of complex solvation processes occurring in supercritical fluid media.
Determination of Bromine Levels in Brominated Polystyrenes and Poly(2,6-Dimethyl-1,4-Phenylene Oxide)s
Authors: Williams E. A. , Frame E. M. Skelly , Donahue P. E. , Marotta N. A. , Kambour R. P.
Published: June 2005

Brominated copolymers of polystyrene and poly(2,6-dimethyl-1,4-phenylene oxide) are highly useful for polymer blend miscibility studies. Bromine levels in these copolymers have been measured with the use of 13C NMR and titration methods. The methods have been evaluated with respect to speed, accuracy, and precision, as well as structural information provided by the technique. Although better precision is obtained with the titration method, the NMR method produces adequate data for these studies. In addition, 13C NMR provides information about the sequencing in the polymer chain from which the randomness of the copolymer can be determined.
Determination of Beryllium by Infrared Spectrometry
Authors: Aller A. J.
Published: June 2005

A simple, rapid, and selective infrared spectrometric method for the determination of beryllium is demonstrated. In this scheme, beryllium is extracted as acetylacetonate into chloroform, and the organic phase is sprayed onto a sodium chloride disk. Then the disk is inserted into the sample compartment of an infrared spectrometer for measuring beryllium concentrations. By this method, spectra may be obtained at sensitivities in the nanogram range. The band at 1215 cm−1 assigned to the µBeO vibrations was used as the analytical line.
The Use of Diffuse Reflection FT-IR Spectroscopy for the Quantitative Analysis of a Number of Silanized Kaolin Clays
Authors: Porro T. J. , Pattacini S. C.
Published: June 2005

This paper deals with the use of FT-IR diffuse reflectance measurements for the monitoring of silane-treated naturally occurring kaolin clays. We show quantitative results for three of the most common silanized clays including precision and accuracy data obtained from neat, unprocessed samples. No Kubelka-Munk correction was required since the Δlog (1/ R) values measured were very low, as determined by comparison with Kubelka-Munk corrected data.
Pressure Sensitivity of Emission Intensities and Plasma Voltage for a Planar Magnetron Glow Discharge
Authors: McCaig Lori , Sesi Norman , Sacks Richard
Published: June 2005

A glow discharge device is described which uses a curved magnetic field passing through the surface of a planar cathode in order to trap electrons near the cathode surface and thus obtain stable operation at unusually low pressures. The magnetic field is obtained from a ring-shaped ceramic magnet and a coaxial Co-Sm rare-earth magnet located directly behind the cathode. In Ar, the device operates over the pressure range 6 × 10−4 Torr to over 2.5 Torr with plasma voltage under 420 V. Plasma voltage vs. pressure data for Cu and Al cathodes suggest that several modes of operation occur over this pressure range. Emission intensity vs. pressure data are presented for Ar, Ar+, Cu, Al, continuum background, and some residual-gas band systems.
Investigation of Background Signals from Na as a Source of Interference in Laser-Enhanced Ionization Spectrometry in Flames
Authors: Axner O. , Norberg M. , Rubinsztein-Dunlop H.
Published: June 2005

Laser-Enhanced Ionization (LEI) signals from Na have been investigated by the one-step excitation scheme in flames in the UV region (220–410 nm). This knowledge is of importance for the applicability of the LEI technique since Na often exists as a matrix in a number of samples and gives rise to background signals. In the wavelength region between 220 and 240 nm, photoionization of ground-state atoms is responsible for the LEI signal. Between 240 and approximately 300 nm, the LEI signal originates mainly from wing-excitations of the ordinary 3 s-np ( n ≤ 5) transitions. Finally, in the wavelength region above the 3 s-4 p transition (i.e., approximately 360–410 nm), the LEI signal consists mainly of photoionization of the thermally excited 3 p state. A theoretical treatment of the various contributions shows good agreement with experiments. It is furthermore found that the LEI sensitivity at 408 nm (the threshold wavelength for photoionization of atoms in the first excited state, the 3 p state) is 50 times smaller than the LEI sensitivity at 240 nm (the threshold wavelength for photoionization of ground-state atoms). The selectivity between analyte atoms (Bi and Pb in the present study) and Na is also studied. It is shown that the analyte-versus-Na selectivity decreases considerably as a function of increased laser intensity. It is concluded that there exists an optimum laser intensity for the most efficient detection of a particular element in a certain Na matrix. This optimum intensity, however, is determined by factors which are specific to each experimental setup.
Quantum-Statistical Modeling of Mixed Inert Gas ICPs
Authors: Fannin H. B.
Published: June 2005

Relative populations of excited neutral and ionic states in reduced-pressure ICPs supported by a binary mixture of helium and an additional inert gas have been shown to obey Fermi-Dirac statistical counting. A single thermodynamic temperature of 2000 K is sufficient to define the distribution of both neutral and ionic state populations. High-energy states of ionic species exhibit a “blending” between Fermi-Dirac and Boltzmann behavior. Agreement between measured relative populations and the Fermi-Dirac distribution is ∼1% overall.
Complications to the Use of Theta-Pinch Discharges for Quantitative Analysis
Authors: Scheeline Alexander , Lee Gae Ho , White Jeffrey S.
Published: June 2005

Initial analytical results are reported for the direct elemental analysis of ceramics using a theta-pinch discharge. Sampling of refractory substances, including detection of minor and trace impurities, is demonstrated. Effects of sample aging and specimen shape are shown. Changes in emission time behavior are attributed to the effects of particle size and apparent nonrepresentative sampling, and to line reversal.
Reduction of Spectral Interferences from Na in Laser-Enhanced Ionization Spectrometry by Laser Pre-Ionization
Authors: Axner O. , Norberg M. , Persson M. , Rubinsztein-Dunlop H.
Published: June 2005

Pre-ionization of Na atoms prior to the analysis of other analyte atoms using the Laser-Enhanced Ionization (LEI) technique in flames has been investigated in order to reduce the influence of spectral interferences (in this case of Na) to the measured LEI signal. A large fraction of the Na atoms present in the flame was ionized with the use of one laser system. A short time later (400 µs) another laser system was aimed at a position 4 mm above the first laser in the flame, thus probing the part of the flame in which the concentration of (neutral) Na atoms had been significantly reduced. Different excitation schemes were used for the preionization process. It was found that the degree of depletion of Na was 13% when the atoms were first excited to the 3 p state by 589-nm light and then photoionized by focused pump laser light (308 nm). When the atoms were excited in two resonant steps (3 s-3 p-7 d), 80% of all the Na atoms could be depleted. With all three lasers illuminating the atoms, finally, 83% of the Na atoms were depleted. (If laser-enhanced chemical processes can be neglected within the duration of the laser pulse, which is most probable in the case of ns pulse duration, the degree of depletion is equivalent to the degree of ionization.) The second laser system was then used for studies of the LEI signal from other elements in the same manner as above. It was then found that this Na pre-ionization did not interfere in any way with the detection of other elements which were detected 400 μs later (4 mm higher in the flame). This was illustrated by a measurement of Mg in a Na matrix in which the Mg signal recovery was 100% while the Na signal was decreased by a factor of 5 (resulting in a corresponding increase in selectivity).
Fourier Transform Raman Spectroscopy of Photoactive Proteins with Near-Infrared Excitation
Authors: Johnson Carey K. , Rubinovitz Ronald
Published: June 2005

The Fourier transform (FT) Raman spectroscopic treatment of the photoactive proteins bacteriorhodopsin and the photosynthetic reaction center is reported, with excitation at 1.06 µm. Excitation at this wavelength circumvents the limitations on resonance Raman spectroscopy of these proteins imposed by their photolability and by the fluorescence of free pigments or impurities. The spectra are dominated by nonresonant Raman scattering by the protein-bound pigments retinal (in bacteriorhodopsin) and bacteriopheophytin, bacteriochlorophyll, and carotenoids (in reaction centers). The relative intensities of retinylidene modes in the spectrum for nonresonant FT Raman spectroscopy of bacteriorhodopsin are nearly identical to those observed in the resonance Raman spectrum of bacteriorhodopsin.
Absorption Spectroscopy in Laser-Generated Plumes by Surface Reflection
Authors: Pang Ho-Ming , Yeung Edward S.
Published: June 2005

Absorption measurements can be used to study the laser-generated plume even at the very initial moments of plume formation. This new optical scheme is based on reflecting a probe beam off the surface. A high degree of penetration of the plume is possible at high probe powers. Saturation of the absorption is found to occur at higher powers than normal. Relatively broad spectral features due to pressure broadening have been obtained.
An Optimized Single-Channel System for Quantitative Raman Spectroscopy of N2 and O2
Authors: Pipino Andrew C. R.
Published: June 2005

A Raman spectrometer has been constructed and optimized for quantitative measurement of N2 and O2 partial pressures. Detection limits of 54 and 62 mTorr are found for oxygen and nitrogen, respectively. The single-channel, single-dispersive-element system incorporates a high-power argon-ion laser and an optical configuration designed for maximum throughput. No D/A-A/D conversions are used. The design and performance of the instrument are discussed. Application of the system to nondestructive monitoring of air contamination in argon-filled insulating glass windows is briefly discussed. Interferometric effects from glass are considered.
Raman Spectroscopic Identification of Uric-Acid-Type Kidney Stone
Authors: Kodati Venkata Ramana , Tu Anthony T. , Turumin Jacob L.
Published: June 2005

Kidney stones of the uric acid type were examined by Raman spectroscopy. The fingerprint pattern of the Raman spectra of these stones matched those of uric acid better than those of sodium urate. Although the Raman spectra of most stones were masked by the high fluorescence of the stones, with the use of a computer to correct the baseline, the Raman scattering bands became distinct. Uric acid has distinct Raman bands at 472, 562, 627, 784, 885, 999, 1039, 1122, 1234, 1288, 1046, 1499, 1595, and 1652 cm−1. The kidney stones examined also showed these bands, indicating that the stones were the uric acid type. Raman spectroscopy is a useful analytical tool for identifying the composition of kidney stones without much sample preparation.