bluuebunny/crossref_metadata_2025 huggingface dataset:
Polarization-Modulation FT-IR Reflection Spectroscopy Using a Polarizing Michelson Interferometer
Authors: Ishida Hatsuo , Ishino Yuichi , Buijs Henry , Tripp Carl , Dignam Michael J.
Published: July 2005

We report the first results obtained on a mid-IR FT spectrometer equipped with a polarizing Michelson interferometer (PMI), and the application examples of polarization spectroscopy are illustrated. A relatively simple method for conversion of a conventional instrument to PMI operation is designed. Specular reflection spectra of poly(vinyl acetate) film on copper and ATR spectra of a Langmuir-Blodgett film on silicon prism are presented.
Sheath Flow Focusing in Supersonic Jet Spectroscopy
Authors: Stiller Steven W. , Johnston Murray V.
Published: July 2005

The mechanism of cooling in sheath-flow-focused supersonic jet expansions is examined. Cooling is found to be strongly influenced by the sheath gas flow properties but independent of the carrier gas in the sample stream. These results indicate that considerable turbulence and mixing between the sheath and sample gases occur downstream from the orifice. However, mixing cannot be complete, since, relative to results with a conventional jet expansion, a substantial enhancement of analyte is obtained along the centerline of a sheath-flow-focused jet expansion. Spectral broadening at “high” analyte mass flow rates within the sample stream is found to arise from inefficient cooling. There are limits to both how large and how small the nozzle orifice can be. Small orifices result in spectral broadening, even at very low analyte mass flow rates. Large orifices may have Reynolds numbers sufficient to cause turbulent flow, which degrades the focusing effect. The optimum nozzle geometry and gas flow conditions for sheath-flow-focused jet expansions are discussed.
Excited-State Triplet-Triplet Absorption in αNPO
Authors: Dharamsi A. N. , Hassam A. B.
Published: July 2005

Time-resolved excited-state triplet-triplet absorption measurements in αNPO solutions were performed. A concentration quenching effect on the excited absorption and fluorescence spectra, due to excimer formation, was seen. A numerical analysis of the results yielded the rate constants for intersystem crossing, triplet quenching by O2, triplet self-quenching, and excimer formation.
Suppression of Luminescence Background in Raman Spectroscopy by Means of Transient Optical Depletion of Causal Impurity Molecules
Authors: Hamaguchi H. , Tahara T. , Tasumi M.
Published: July 2005

A simple but highly efficient method of luminescence quenching in Raman spectroscopy is proposed—made on the basis of a newly recognized phenomenon which is ascribable to the optical depletion of luminescent impurity molecules by pulsed-laser excitation. The method has been applied to two typical biological samples: a DNA tetramer (AATT; adenine-adenine-thymine-thymine) and a protein (calmodulin). Suppression of luminescence background by factors of 10–100 was achieved by changing the mode of excitation from cw to pulsed. A model calculation based on semiquantitative estimation of photoexcitation rates successfully accounts for the observed quenching efficiency.
Energy Calculation with Guaranteed Error Bounds for the States of Para-Helium Singlets from Spectral Measurements
Authors: Greenspan Donald
Published: July 2005

A simple but modern numerical approach to error analysis is applied to spectral measurements for para-helium singlets to yield energy states. The methodology yields approximations with guaranteed error bounds and can be extended in a natural way to other atomic species.
Examinations of the Matrix Isolation Fourier Transform Infrared Spectra of Organic Compounds. Part V
Authors: Coleman W. M. , Gordon Bert M.
Published: July 2005

MI/FT-IR spectral data have been collected on selected types of organic compounds containing the carbonyl group. By the varying of the ratio of the matrix gas to the compound ( M/E) as well as the matrix gas (Ar vs. Xe), the observed splitting of the carbonyl absorption band was attributed to both conformer isolation and aggregation in the matrix. The splitting of the carbonyl group of methyl acetate was attributed to aggregation, while conformer isolation was found to exist for phenyl acetate and trimethylacetaldehyde. The magnitude of the splittings found in this study, 3–30 cm−1, is within the range of values found for other organic compounds. Band splitting was shown by (1) compounds that are linear and contain ≤5 carbons or (2) compounds that are branched and contain <5 carbons. Compounds having >5 carbons displayed only band broadening. Varying M/E ratios has been found to be a reasonable method by which to distinguish between conformer and aggregation. These data confirm the influence of sample phase and indicate that extreme care must be taken in the use of MI/FT-IR spectra as physical probes for structure determination.
Emission Spectroscopy Utilizing an Air-Cooled Argon Laser and an Optrode-Based UV-Vis Spectrophotometer: A Scaled-Down Laser Spectroscopy Configuration for Solution-Phase Fiber Optic Sensing
Authors: Reichert W. M. , Ives J. T. , Suci P. A.
Published: July 2005

The sensitivity of a scaled-down emission spectroscopy configuration was tested with the use of (1) the fluorescence from Rhodamine 6G in ethanol and (2) the Raman emission from acetone, toluene, methanol, and water. The fluorescence results showed a linear intensity response down to a concentration of 3.17 × 10−7 mg/mL, which corresponded to sensitivity of four parts per ten billion by weight. Nonlinear signal levels extended the sensitivity almost two more orders of magnitude lower in concentration. The observation of Raman emission indicated that this system was sensitive enough to detect very weak intensities but was two to three orders of magnitude too insensitive to produce a practical Raman sensor.
Fundamental Characteristics of Thermospray Aerosols and Sample Introduction for Atomic Spectrometry
Authors: Koropchak John A. , Winn D. H.
Published: July 2005

Sample introduction to inductively coupled plasma atomic emission using thermospray nebulization is studied at a fundamental level. Optimum signals and signal-to-noise ratios result from thermospray operation at temperatures which coincide with highest analyte transport (>20%). High transport levels are maintained at sample flow rates of up to 3 mL/min. On the basis of comparison with analyte transport measurements for a pneumatic nebulizer (1.5%), signal increases are less than anticipated. Measurement of primary thermospray aerosols, using Fraunhofer diffraction, indicates that the enhanced transport results from decreased particle sizes for thermospray aerosols compared with pneumatic aerosols. Solvent is more rapidly vaporized from hot thermospray aerosols, further increasing the disparity in particle sizes. On the basis of aerosol particle size data, a conceptual model for aerosol generation, which is similar to pneumatic processes, is developed for thermospray. Trends for further improvements in thermospray aerosol production are predicted.
Direct Supersonic Expansions of Supercritical Fluids for Analysis of Polycyclic Aromatic Hydrocarbons
Authors: Goates S. R. , Barker A. J. , Zakharia H. S. , Khoobehi B. , Sheen C. W.
Published: July 2005

Significant line-narrowing has been observed in the laser-induced fluorescence spectra of naphthalene and perylene in direct supersonic expansions of simple supercritical carriers such as CO2, N2O, and even SF6, under conditions which minimize aerosol and cluster formation. Clusters form readily in expansions of CO2 and N2O unless nozzle temperatures exceed about 200°C. Results with more complex carriers, such as n-pentane, are much poorer. Selective detection of perylene at a limit of 2 ng (S/N = 3) in a mixture of ten polycyclic aromatic hydrocarbons and in a coal tar extract has been achieved with a capillary introduction system. Challenges with coupling supersonic jet detection to capillary supercritical fluid chromatography lie with the nozzle.
Hadamard Transform Visible Raman Spectrometry
Authors: Tilotta David C. , Freeman Robert D. , Fateley William G.
Published: July 2005

The successful application of LC-SLM Hadamard transform spectrometry as a simultaneous multiwavelength detection system to Raman spectroscopy is presented. Multiplexed Raman data are obtained with the use of an Ar+ laser lasing at 514.5 nm and a room-temperature silicon photodiode. A conventional 90° scattering geometry is employed for measurements. It is demonstrated that the LC-SLM Hadamard transform Raman spectrometer possesses the capability of performing spectral subtraction and the ability to obtain depolarization ratios of Raman bands, and can function as a selectively tunable optical filter for both Rayleigh line rejection and optical band notching. It is also demonstrated that, for the Hadamard transform Raman experiment, the silicon photodiode used as the detector produces spectra with slightly better signal-to-noise ratios than those obtained with the photomultiplier tube (PMT) used as the detector, although the PMT shows an increase in sensitivity.
Identification of Polychlorinated Pyrenes and Pyrene-Addition Products Using Proton Nuclear Magnetic Resonance Techniques
Authors: Ashley David L. , Barnhart Elizabeth R. , Patterson Donald G. , Hill Robert H.
Published: July 2005

Nuclear magnetic resonance (NMR) techniques are used to determine the chlorination pattern on a number of chlorinated pyrenes and pyrene-addition products. Determining chemical shifts, couplings, and longitudinal relaxation rates makes the unequivocal assignment of these molecules possible. Chlorination under the conditions described here were found to follow the normal orientation rules for pyrene. Spectral parameters obtained from these molecules are consistent enough to allow further application to unknown compounds. This should simplify assigning NMR spectra to other chlorinated pyrene standards.
Spectrochemical Measurements with Multichannel Integrating Detectors
Authors: Bilhorn R. B. , Epperson P. M. , Sweedler J. V. , Denton M. B.
Published: July 2005

This is the second article in a two-part series describing the operation, performance characteristics, and spectroscopic application of charge transfer devices (CTDs) in analytical chemistry. The first article in the series describes the new generation of integrating multichannel detectors, the charge injection device (CID), and the charge-coupled device (CCD). The first article also discusses the spectroscopically pertinent characteristics of these detectors and presents performance data for representative devices. This article covers three major topics related to the optimum use of integrating detectors in analytical spectroscopy. The advantages of employing integrating multichannel detectors in analytical spectroscopy, rather than a single detector in a wavelength scanning system or an interferometer, are discussed. Included are detector read noise considerations which have not been considered in previous performance comparisons. When one is employing an integrating detector in luminescence, absorption, and emission applications, achievable sensitivity is dependent on differing detector parameters. In the first case, quantum efficiency and read noise are of the greatest importance, whereas in the later two cases, dynamic range is most significant. The calculation of minimum detectable analyte signal for these three techniques illustrates the differences between integrating detectors and detectors which produce a photocurrent. This discussion also illustrates the great sensitivity that can be achieved with a modern CTD detector. Factors pertaining to the optical design of spectrometers which efficiently use CTDs are presented, along with examples of linear and two-dimensional dispersive polychromators employing CTDs. Low-light-level imaging and a nonconventional method of using a CCD for rapid scanning spectrophotometry are also discussed.
Spectral Searching by Fourier-Phase Correlation
Authors: Kawata S. , Noda T. , Minami S.
Published: July 2005

A new idea of spectral library searching is proposed, in which only the phase components of Fourier transforms of both the sample and the reference spectra are used for spectral identification. Compared with the conventional methods, this method has essentially a very high discrimination ability for distinguishing between similar spectra and is very resistant to the peak-height variation and the peak-position shift due to the experimental conditions. The principle and the algorithm of this library search method are described, along with the experimental results for infrared absorption spectra. The results demonstrate that the proposed method gives much lower scores for wrong reference spectra than does the ordinary correlation method, and gives high scores for the sample spectra measured by the various slit widths of the spectrophotometer.
Raman Spectroscopy Using dc Signal Detection and a Microcomputer: An Alternative Approach
Authors: Lewis E. Neil , Levin Ira W.
Published: July 2005

Raman spectroscopic data have been obtained with the use of direct current (dc) signal detection, an IBM PC/AT microcomputer, and commercially available software. Since photomultiplier currents of the order of nanoamps to microamps are readily attained for Raman emission under conditions of moderate laser excitation power levels (150–200 mW) and medium resolution spectral slits (1–4 cm−1), signal levels well within the domain measurable by dc signal detection techniques are achieved for a wide range of chemical and biochemical samples. Further, the digitization and signal averaging capabilities of generic data acquisition boards and microcomputers allow dc detection to yield signal-to-noise ratios competitive with those derived from complementary pulse-counting techniques.
Diffuse Reflectance and Photoacoustic Fourier Transform Infrared Spectra of Silica Surfaces under Polarizable Gases
Authors: Story W. Charles , Masujima Tsutomu , Liang Jim , Liu Guangyue , Eyring Edward M. , Harris Joel M. , Anderson Larry L.
Published: July 2005

It has been reported that the use of an infrared transparent polarizable gas such as xenon enhances the FT-IR photoacoustic signal of some species adsorbed on a sample surface. Diffuse reflectance and photoacoustic FT-IR methods were used to obtain spectra of silica surfaces under helium, nitrogen, and xenon. Absence of the reported effect with both techniques is shown, and a tentative explanation for these results is given.
Fluorescence Lifetime Study of Cyclodextrin Complexes of Substituted Naphthalenes
Authors: Nelson Gregory , Patonay Gabor , Warner Isiah M.
Published: July 2005

The interactions of α, β, and -γ-cyclodextrins and selected naphthalene derivatives as observed through fluorescence lifetime measurements are discussed in detail. These systems can be quickly characterized with the use of the parameters obtained from experimental fluorescence decay curves. The formation of inclusion complexes can be followed with the appearance of a long-lived fluorophore which contributes to the total fluorescence according to the cyclodextrin concentration. This fluorophore is determined to be an inclusion complex between a naphthalene and cyclodextrin.
Thermal Decomposition of Energetic Materials 26. Simultaneous Temperature Measurements of the Condensed Phase and Rapid-Scan FT-IR Spectroscopy of the Gas Phase at High Heating Rates
Authors: Cronin J. T. , Brill T. B.
Published: July 2005

Rapid-scan infrared spectroscopy (RSFT-IR) with better than 100-ms temporal resolution has been used to quantify the gas decomposition products of energetic materials in real time at various heating rates up to 800°C/s and under buffer gas pressures of 1 to 1000 psi. A new method is described that permits simultaneous real-time recording of the temperature of the condensed phase and of the IR spectra of the gaseous products under the above conditions. Endothermic and exothermic events in the condensed phase can now be correlated with the evolved gases under conditions approaching those of combustion. The design and procedure for using the cell are given and are applied to the thermolysis of 1,7-diazido-2,4,6-trinitro-2,4,6-triazaheptane (DATH) and pentaery-thrityltetrammonium nitrate (PTTN).
Surface Enhanced Raman Spectrometry on Silver Hydrosols Studied by Flow Injection Analysis
Authors: Berthod Alain , Laserna Jose J. , Winefordner James D.
Published: July 2005

Surface enhanced Raman scattering (SERS) corresponds to the increase of the Raman scattering cross section of organic molecules (five to six orders of magnitude) when molecules are adsorbed onto metal surfaces. The use of silver hydrosols, obtained by chemical reduction of silver nitrate solutions, is convenient. An important drawback is irreproducibility of hydrosol preparation procedures and the nonlinearity between the SERS response and the analyte concentration. In order that these problems could be overcome, flow injection analysis (FIA) has been used. With FIA, constant, reproducible silver hydrosol formation results. SERS signals of para-aminobenzoic acid (PABA) were measured over four orders of magnitude of concentration range and over three pH units. The precision of FIA-SERS signals for PABA was 5%, and the limit of detection of PABA was in the ppb range with the use of the Raman band at 1605 cm−1 with an Ar+ laser at 514.5 nm.
Charge Transfer Device Detectors for Analytical Optical Spectroscopy—Operation and Characteristics
Authors: Bilhorn R. B. , Sweedler J. V. , Epperson P. M. , Denton M. B.
Published: July 2005

This article is the first in a two-part series describing the operation, characteristics, and application of a new class of solid-state multichannel UV-visible detectors. In this paper, charge transfer devices (CTDs) are described. Detector characteristics pertinent to spectroscopic application—including quantum efficiency, read noise, dark count rate, and available formats—are emphasized. Unique capabilities, such as the ability to nondestructively read out the detector array and the ability to alter the effective detector element size by a process called binning, are described. CTDs with peak quantum efficiencies over 80% and significant responsivity over the wavelength range of 0.1 nm to 1100 nm are discussed. Exceptionally low dark count rates, which allow integration times of up to many hours and read noises more than two orders of magnitude lower than those read by commercially available PDA detectors, contribute to the outstanding performance offered by these detectors.
Single-Laser, Single-Beam Pump/Probe Thermal Lens Spectroscopy
Authors: Erskine Steven R. , Foley C. Michael , Bobbitt Donald R.
Published: July 2005

A unique design for a thermal lens photometer based on a single-laser/single-beam configuration is presented. The system is compatible with lock-in detection and uses a pair of acoustooptic modulators to temporally separate the pump and probe events. A minimum measurable absorbance of 6 × 10−6 cm−1 is reported. Limitations to the use of acoustooptic modulation at high absorbances are discussed.
Investigation of Experimental Parameters for Surface-Enhanced Raman Scattering (SERS) Using Silver-Coated Microsphere Substrates
Authors: Moody R. L. , Vo-Dinh T. , Fletcher W. H.
Published: July 2005

The effects of experimental parameters on surface-enhanced Raman scattering (SERS) for silver-coated microsphere substrates were investigated. The parameters included sphere size, silver thickness, and excitation wavelength. The SERS signal intensity varied as each of these parameters was changed. The potential for increasing SERS sensitivity was illustrated by the detection of benzo(a)pyrene, a molecule of environmental and toxicological interest, at a concentration well below that possible for normal Raman scattering. This work describes some optimization procedures and demonstrates the possibility for further improving SERS enhancement of these silver-coated microsphere substrates by optimizing experimental parameters.
Channel and Analyte Dynamics in the High-Voltage Spark Discharge Using Raman, Fluorescence, and Emission Spectroscopies
Authors: Zoellner Michael J. , Scheeline Alexander
Published: July 2005

An investigation was made of the use of laser light scattering and laser-induced resonance fluorescence, employed in combination with spontaneous emission, as diagnostic probes of the atmospheric-pressure high-voltage spark discharge, to elucidate information on various species. Raman scattering allowed the space- and time-resolved investigation of N2 behavior in the spark channel. Emission profiles of Al(I) and AlO were obtained to establish the temporal regions that were nonemitting for each species. Resonance fluorescence permitted observation of aluminum species in the nonemitting post-discharge torus both spatially and temporally resolved. The channel dynamics studies revealed the interaction of atmospheric nitrogen with the spark channel. Fluorescence studies on aluminum as the analyte species revealed the presence of Al(I) and AlO in the post-discharge torus region, after the discharge current has ceased, and after the Al(I) and AlO emission has ceased. This establishes that analyte material exists in more than one chemical form in the nonemitting regions of the spark discharge, and that excitation decays before all free atoms recombine into small molecules.
Near-Infrared Reflectance Analysis of Iron Ores
Authors: Fredericks Peter M. , Tattersall Alan , Donaldson Ralph
Published: July 2005

Near-infrared reflectance analysis (NIRA) has been applied to the rapid characterization of mineral samples. A suite of 82 West Australian iron ores was used to carry out the work. Approximately half the samples, chosen randomly, were used as a calibration set, while the remaining samples formed a prediction test set. Correlations were sought for eight of the significant practical properties of the samples. These properties were major element analysis, combined water, relative density, and goethite concentration. Reasonably close correlations were obtained for most of the properties, except silicon, although the estimated prediction errors were worse than those obtained with conventional methods. Nevertheless, the speed and simplicity of the NIRA method should make it of use in many quality-control applications. The relatively poor result for silicon is probably due to the transparency of quartz in the near-infrared region.
Continuous-Wave CO2 Laser-Excited Infrared Emission Spectroscopy
Authors: Belz H. H. , Gutberlet H. , Schallert B. , Schrader B.
Published: July 2005

Radiation of a cw CO2 laser can be used to excite infrared emission spectra of nearly all molecular gases by adding small amounts of SF6 as a sensitizer. These emission spectra show a thermal equilibrium between vibrational, rotational, and translational states with temperatures up to 1200 K. Temperature profiles of these gases about a focused cw CO2 laser beam are analyzed by Raman spectroscopy. The detection of small amounts of sample and investigations of cw laser-induced chemical reactions are interesting potential applications.
High-Voltage Spark Spectra: Utility as a Function of Temporal and Spatial Resolution
Authors: Cousins Jennifer Cappel , Scheeline Alexander , Coleman David M.
Published: July 2005

The utility of the high-voltage spark discharge as an analytical emission source is considered. Temporal and spatial windowing was used to reiterate well-documented characteristics of heterogeneities of the spark plasma in both time and space. Cathodes of pure magnesium and aluminum 2024 alloy were used as samples. It was shown that by using a unidirectional current waveform, and by selecting a spatial position off of the interelectrode axis, at times late in the plasma lifetime, one can obtain relatively clean emission spectra (high signal-to-background ratio). This is in contrast to recent literature reports which suggest that the high-voltage spark exclusively produces spectra which are complex and which demonstrate poor background characteristics. The dynamic range of the spark is also demonstrated to be somewhat larger than the cited work suggests. The implications of various methods of presenting experimental results for such data are discussed.
Spectroscopic Studies of Interactions between Styrene/Acrylic Acid Copolymer and Sodium Dodecyl Sulfate
Authors: Urban Marek W. , Koenig Jack L.
Published: July 2005

The results obtained from Fourier transform infrared study of sodium dodecyl sulfate (SDS) in water and in the presence of styrene/acrylic acid (S/AA) copolymer are presented. The C-H stretching band of the SDS hydrocarbon tail at 2929 cm−1 and the O-H stretching of H2O are sensitive to changes in the SDS concentrations. With the increasing concentration both bands are shifted to lower frequency. A mutual presence of S/AA copolymer and surfactant in the aqueous solution leads to a splitting of the bands due to COO− groups. It is proposed that the splitting is due to interactions between COO− segments of the copolymer and the “surfaces” of micelles through the Na+ or Li+ ions.
Matrix Isolation FT-IR Studies of Nitro Polycyclic Aromatic Hydrocarbons
Authors: Stout Philip J. , Mamantov Gleb
Published: July 2005

Nitro polycyclic aromatic hydrocarbons (nitro-PAH), a class of compounds which has a number of anthropogenic sources, are potent mutagens. The application of matrix isolation Fourier transform infrared spectroscopy (MI/FT-IR) to the analysis of nitro-PAH was demonstrated. Samples were vaporized in a Knudsen cell and co-deposited with nitrogen on a CsI window cooled to 15 K. Spectra of twelve compounds were obtained for the purpose of forming a partial library of matrix-isolated nitro-PAH. Qualitative studies demonstrated the resolution and identification of components of complex and isomeric mixtures. The feasibility of quantitative analysis of nitro-PAH was demonstrated with the construction of a Beer's law plot of 1-nitropyrene. The plot was linear over two decades.
Quantitation of Metals in Liquid Samples by Computer Intelligent Flow Injection Inductively Coupled Plasma Emission Spectrometry
Authors: Martin John M. , Ihrig Philip J.
Published: July 2005

With the advent of commercial flow injection equipment, the means became available for the automated computer intelligent sample handling for ICP analysis. This paper will describe our system, which consists of a 36-channel ARL 34000 ICP spectrometer and a FIAtron SHS-300 flow injection instrument. The functions that the system will perform include (1) automatic analysis of undiluted samples with sample introduction by flow injection, (2) automatic operator-selectable fixed dilution and analysis of samples, (3) automatic analysis of samples using computer-guided sequential dilutions to place all elements within the optimum calibration curve range, (4) the use of merging streams to achieve sample dilutions of ∼200-fold, and (5) the automatic addition of standards to a sample and then sample analysis for a standard addition study. By use of the automatic sample changer, up to 76 samples of widely varying concentrations may be analyzed completely without operator intervention. Furthermore, all analyses will be made within the optimum calibration curve range for each element. Additional benefits of the flow injection system include improved plasma stability, improved system precision and accuracy, and lower detection limits for many elements. The means by which these operations can be performed will be described, and data will be presented from the development and use of the system.
Selective Observation of Species in High-Voltage Spark Discharges Based on Transient Magnetic Field Perturbation
Authors: Majidi Vahid , Coleman David M.
Published: July 2005

The behavior of an analytical spark discharge in a pulsed external magnetic field is described. Time-resolved spectroscopic data indicate the spatial isolation of ionic species. Time-integrated, spatially resolved data further demonstrate that the region of maximum emission intensity (for ionic species) is shifted 1100 μm, with respect to the interelectrode axis, when the magnetic field is energized. Emissions from neutral species are influenced to a lesser extent.
Evaluation of Infrared Vapor-Phase Libraries for Matrix Isolation Spectral Searching
Authors: Rogers Michael L. , White Robert L.
Published: July 2005

By broadening matrix isolation absorbance bands to match vapor-phase bandwidths, it is possible to employ vapor-phase libraries to provide structural information from matrix isolation infrared spectra. However, matrix effects cause frequency shifting and peak multiplicity in matrix isolation spectra which decrease correlation between matrix isolation and vapor-phase spectra. The effect of matrix effects on library search results is investigated. Of 40 matrix isolation spectra tested, 28 were identified by library search with the use of a band-broadening factor of 1.8.
Quantitative Estimation of α-Helix Coil Content in Bovine Serum Albumin by Fourier Transform-Infrared Spectroscopy
Authors: Kato Kenji , Matsui Tomoko , Tanaka Sigeyuki
Published: July 2005

Heat denaturation of albumin aqueous solution enables us to control the α-helix content to a reasonable level, and denatured albumin, whose conformation is different, can be obtained. Fourier transform-infrared absorption spectra in the amide I, II, and III band regions of these albumins have been measured and compared with each other. As a result, the characteristic frequencies associated with each conformation of α-helix, β-sheet, and random structure have been observed; moreover it has been newly proved that the intensity ratio of the amide II band to the amide I band depends on the α-helix content in albumin. In this paper, we demonstrate that this intensity ratio is very useful for quantitative estimation of α-helix content in albumin and apply this method to analysis of ATR spectra of albumin adsorbed on polyethylene surface.
Antibody-Based Fiberoptics Biosensor for the Carcinogen Benzo(a)pyrene
Authors: Vo-Dinh T. , Tromberg B. J. , Griffin G. D. , Ambrose K. R. , Sepaniak M. J. , Gardenhire E. M.
Published: July 2005

A new antibody-based fiberoptics biosensor was used to detect the important carcinogen benzo(a)pyrene (BaP). The fiberoptics sensor utilizes anti-BaP antibodies covalently bound to its tip. A helium cadmium laser was used as the excitation source to induce fluorescence from BaP conjugated to the bound anti-BaP antibodies. The fiberoptics device can detect 1 femtomole of BaP in a 5-μL sample drop.
Infrared Study of Styrene-Acrylonitrile Copolymer at Variable Temperature
Authors: Nyquist R. A.
Published: July 2005

IR spectral data for a copolymer of acrylonitrile-styrene at temperatures ranging from 30 to 277°C are reported.
Resonance Raman Analysis of Fluorescent Compounds Using Micellar Solutions and Ultraviolet Laser Excitation
Authors: Spino Larry A. , Armstrong Daniel W. , Alak Ala M. , Vo-Dinh Tuan
Published: July 2005

Micelles composed of specifically functionalized surfactants can be used to great advantage in resonance Raman spectroscopy. In addition to circumventing the problem of luminescence background, micelles allow the use of aqueous solvents which stabilize labile species and improve the signal-to-noise ratio. The first examples of micelle-mediated resonance Raman analysis of fluorescent compounds using ultraviolet excitation are given.
The Effect of Metal Substrate (Al, Cu, Ag, and Au) on the Photodegradation of Polymers: Polyacrylonitrile
Authors: Welch W. F. , Graham S. M. , Chughtai A. R. , Smith D. M. , Schissel P.
Published: July 2005

Al-backed PVF film shows more photodegradation than does the non-metalized PVF film. The effect of several metal substrates (Al, Cu, Ag, and Au) on the photodegradation of polyacrylonitrile (PAN) has been examined. Under oxidative conditions, the order of PAN photodegradation in M/PAN films is shown to be Cu/PAN » PAN » Al/PAN > Au/PAN > Ag/PAN. Formation of carbonyl group during the photodegradation is predominant in the cases of Al and Au. Under nonoxidative conditions there is no evidence of carbonyl group formation, but the photodegradation of Cu/PAN is still substantial. Under oxidative conditions the Cu/PAN film begins to char after approximately one hour, compared with four and a half hours under nonoxidative conditions. The photodegradation mechanism in the range of 250 ≤ λ ≤ 400 nm suggests the formation of M(CN) x species, but no such species are detected spectroscopically at the energy employed. A catalytic effect of metal films on the photodegradation of PAN is obvious.
Angular Dependence of Diffuse Reflectance Infrared Spectra. Part II: Effect of Polarization
Authors: Brimmer Paul J. , Griffiths Peter R.
Published: July 2005

The magnitude of specular and diffuse Fresnel reflectance from powdered samples was investigated with the use of an FT-IR spectrogoniophotometer with wire-grid polarizers mounted in front of and behind the sample. Specular Fresnel reflectance maintains the polarization of the incoming infrared beam and can therefore be eliminated by crossing the orientation of the second polarizer relative to the first. For neat samples, diffuse Fresnel reflectance was found to be only slightly affected by the presence of the two polarizers. While specular Fresnel reflectance is affected by the optical geometry used in making the reflectance measurement, diffuse Fresnel reflectance is unaffected by optical geometry and can only be eliminated by dilution of the neat sample. For dilute samples, the optical geometry and the orientation of the two polarizers slightly affect the absolute intensity of absorption bands, but do not change relative band intensities or band positions.
The Study of Ternary Metal-Protein-Ligand Complexes Using Bromine-81 Magnetic Resonance
Authors: Pesek Joseph J. , Ronen Sabrina M. , Alcaraz Armando
Published: July 2005

Bromine-81 magnetic resonance is used to detect the formation of ternary metal-protein-ligand complexes. Mercury is the metal; EDTA and lysine are the ligands; and acid phosphatase, α-chymotrypsinogen, and peroxidase are the proteins which are studied. The halide-ion probe method permits the determinations of the local correlation time and the bromide-ion exchange rate at the metal binding site. The local correlation time becomes longer as additional mass in the form of the ligand is added to the protein segment containing the metal binding site. The bromide-ion exchange rate increases upon formation of the ternary complex, which is consistent with the pattern of hetero-substitution in bromomercury (II) species. The major factors controlling the bromide-ion exchange rate appear to be steric.
Comparison of Laser (LMS), Californium-252 Plasma Desorption (252Cf-PDMS), Fast Atom Bombardment (FAB), Secondary Ion (SIMS), and Field Desorption (FD) Mass Spectra of a Series of Internal Salts
Authors: Balasanmugam Kesagapillai , Viswanadham Somayajula Kasi , Hercules David M. , Cotter Robert J. , Heller David , Benninghoven A. , Sichtermann W. , Anders V. , Keough T. , Macfarlane Ronald D. , McNeal Catherine J.
Published: July 2005

Comparison of the mass spectral techniques of Laser (LMS), Californium-252 Plasma Desorption (252Cf-PDMS), Secondary Ion (SIMS), Fast Atom Bombardment (FAB), and Field Desorption (FD) Mass Spectrometry is presented for the positive- and negative-ion spectra of a series of internal salts (zwitterions) known as the sultaines. The spectral characteristics compared are: quasimolecular ions, fragment ions and their implication for structure determination, and cluster-ion formation. Quasimolecular ions corresponding to (M + H)+ (all techniques); (M+CH3)+ (LMS, PDMS, SIMS); (M+R)+ (R = long alkyl chain up to C12, LMS); (M+Na)+ (SIMS, 252Cf–PD); (M+Ag)+ (SIMS), (M–H)− (FAB); (M–CH3)−; and (M–R) were observed (negative-ion FD mass spectra were not obtained). Extensive fragmentation is observed for PDMS and LMS, providing the highest level of structural information. Also, the possibilities for structure elucidation by SIMS are very good. Minimal fragmentation is observed for FAB; however, complete structure elucidation is possible by using both the positive- and negative-ion FAB spectra. FD is a less favored technique for the structural analysis of the sultaines. The negative-ion spectra of sultaines obtained by LMS, PDMS, SIMS, and FAB showed identical peaks in the lower mass ranges ( m/z < (M–CH3)−), although of varying intensities. Cluster ions and solvated (glycerol) cluster ions are observed in negative FAB in the higher mass ranges ( m/z > (M–CH3)−). FAB is unique with respect to cluster-ion formation; cluster ions of high order [( nM + H)+, n = 2–14; ( nM?CH3)−, ( nM–R)−, n = 2–9; ( lM+ mG–H)−, l = 1–4, m = 1–3] are observed. Other techniques show cluster ions such as ( nM+H)+, n = 2–3 (SIMS, PDMS, FD); ( nM+Na)+, n = 2 (SIMS and PDMS); and (2M+Ag)+ (SIMS). No cluster ions were observed in LMS.
Laser-Induced Photoconductivity in Thin Organic Films
Authors: Tierney Michael , Lubman David
Published: July 2005

Photoconductivity in polynuclear aromatic hydrocarbons has been shown to be wavelength dependent and related to the electronic absorption spectrum. Photoconductivity is studied in several PNAHs with the use of light from a pulsed dye laser. The voltage dependence, light intensity dependence, and temperature dependence and the effect of ambient gases on the photocurrent are investigated in thin-film samples on a surface-type cell. The majority charge carriers are holes which flow across the surface of the sample. Photocurrents on the order of microamperes are observed. A preliminary investigation of the effect of temperature on the spectral dependence of the photocurrent shows that the peaks narrow when the sample is cooled to 80 K. This technique may prove useful as a method of obtaining sharp spectra of some organic thin films.
A Visible Near-Infrared Hadamard Transform Spectrometer Based on a Liquid Crystal Spatial Light Modulator Array: A New Approach in Spectrometry
Authors: Tilotta D. C. , Hammaker R. M. , Fateley W. G.
Published: July 2005

A stationary Hadamard encodement mask has been designed from a liquid crystal display. This mask, when properly installed and positioned in a dispersive instrument, allows the selected Hadamard encoded spectral elements to be focused on a single detector. Discussion of the advantages derived by this technique is presented. Several emission spectra in the visible and near-infrared region demonstrate the usefulness of the Hadamard transform technique. This novel spectrometer can provide a no-moving-parts spectroscopy for future spectral applications.
Structural and Quantitative Analysis of Surface Modified Poly(vinylidene Fluoride) Films Using ATR FT-IR Spectroscopy
Authors: Kuhn K. J. , Hahn B. , Percec V. , Urban M. W.
Published: July 2005

The reaction of PVF2 films in aqueous NaOH with the use of tetrabutylammonium hydrogen sulfate as phase transfer catalyst results in surface dehydrofluorination. Subsequent examination of the PVF2 surface using ATR FT-IR affords evidence as to the structure of dehydrofluorinated PVF2. It is found that the infrared bands at 1402, 1225, 1194, and 882 cm−1 are sensitive to the surface treatment. The origin and behavior of these bands are discussed. It is observed that upon dehydrofluorination the FT-IR spectra of the PVF2 surface exhibit two infrared bands at 1613 cm−1 and 1717 cm−1 which arise from the formation of carbon-carbon double bonds. The band at 1613 cm−1 is due to conjugated -(-CH=CF-)- units, whereas the 1717 cm−1 band is assigned to the -(-CF=CF-)- units which arise from resonance at structural head-to-head and tail-to-tail defects.
Odd Moments of the Cross-Correlation Function for Library Searching of Infrared Spectra
Authors: Yu Jung-Pin , Friedrich H. Bruce
Published: July 2005

The odd moments of the autocorrelation function are zero, and the moments of the cross-correlation function for an unknown spectrum with a library entry have been used here to select the best fits. The use of the first moment or average wavenumber in six separate spectral ranges requires only 12 values per library entry, and 24 values are required per library entry if twelve separate ranges are used. The odd moment methods were found to yield results for searches with both library and experimental spectra that were comparable to correlation coefficients in selection of the proper chemical class for the unknown spectra and in making of the proper identification.
Calibration in the Fiber Optic Region of the Near-Infrared
Authors: Tenge Brad , Buchanan B. R. , Honigs D. E.
Published: July 2005

Chemical sensing in remote, hostile environments is possible with optical fiber technology. Telecommunications optical fiber transmits light in the near-infrared region. The least amount of attenuation of transmitted power is between 1050 nm and 1600 nm. It is a natural step to apply near-infrared analysis techniques to data remotely collected over optical fibers. A feasibility study is conducted to see how well calibration techniques, Multiple Linear Regression with either Step-up search or All Possible Combinations search, perform in the fiber optic region of the near-infrared. Calibration in the 1131–1531 nm region is compared to calibration in the 1131–2531 nm region. The latter region is considered more information-rich than the former. In spite of this, examination of the predictive power of calibration models formed strictly from fiberoptic-region absorbance data indicates that this region contains useful analytical informaton.
A Generalized Approach to Derivative Spectroscopy
Authors: Cameron David G. , Moffatt Douglas J.
Published: July 2005

A general approach to obtaining smoothed even-order derivative spectra using Fourier transforms is developed. The method is easier to use and yields higher signal-to-noise ratios than do techniques which involve the use of convolution functions.
Photodiode Array Detection in Analytical High-Resolution Molecular Luminescence Spectroscopy
Authors: Hofstraat J. W. , Engelsma M. , De Roo J. H. , Gooijer C. , Velthorst N. H.
Published: July 2005

It is shown that photodiode arrays can be successfully applied for the detection of highly resolved molecular luminescence spectra for analytical purposes. Instrumental resolution of 0.2 nm, sufficient for the discrimination of structural isomers like monomethylated polynuclear aromatic hydrocarbons, is readily achieved when a suitable monochromator is used. In the experimental setup employed in this study, only a limited spectral region (i.e., about 10 nm) can be observed at a time, but this is no problem when structurally related compounds are studied. These results imply that the detection of highly resolved emission spectra “on-the-fly,” as is required for on-line detection of chromatographically separated compounds in supersonic jets, will be possible. Furthermore, photodiode array detection enables the elimination of time-dependent effects [such as hole burning effects in Fluorescence Line-Narrowing (FLN)] in the spectra. In order that sensitivities similar to those of photomultipliers can be achieved, intensified photodiode arrays are needed.
Infrared Spectroscopy of Surface Films and Powders Using a Metal Light Pipe (Experimental)
Authors: Hansen Wilford N. , Andrew James F. , Hansen Galen J.
Published: July 2005

Light pipe infrared spectra of adsorbed layers and powders are shown. They are compared with specular external reflection, ATR, KBr pellet transmission, and diffuse reflection spectra. The resultant light pipe spectra are found to obey the predictions of the theory presented in the previous companion paper [Appl. Spectrosc. 41, 46–62 (1987)], including the high sensitivity and S/N predicted to be attainable. They are easy to obtain and to interpret. Only fractions of a milligram of sample are required in favorable cases. The light pipe is convenient as a reaction cell, allowing changing spectra to be followed in real time. In the previous paper were presented equations for absorption spectra of thin layers of material on the inner surface of a light pipe, in the infrared. In the present paper the equations are tested against experimental reality. These tests are a crucial verification of the theory.
ICP Rotational Spectroscopic Temperature Determination Using N2 and N2+
Authors: Seliskar C. J. , Miller D. C. , Fleitz P. A.
Published: July 2005

The rotational structure in the origin bands of the Second Positive System of N2 and the First Negative System of N2+ have been used to demonstrate that these bands can be employed to determine a consistent spectroscopic temperature in an ICP. The experimental spectra have been modeled by the use of a computer program which calculates these bands for both species.
Excitation Temperatures in the Microwave-Induced Active-Nitrogen Afterglow
Authors: Hood W. H. , Niemczyk T. M.
Published: July 2005

A systematic study of the excitation temperature obtained from microwave-produced active nitrogen is reported. Iron atoms are used as the thermometric species, and the excitation temperatures are calculated with the use of the two-line ratio method. The excitation temperatures determined cover the range of approximately 3000 K to 4000 K, depending on the region of the plasma viewed. The large difference between the excitation temperature and the thermal temperature, as well as the fact that the excitation temperature is relatively insensitive to operating conditions, gives credence to the excitation mechanism proposed for active nitrogen systems.
Raman Spectroscopic Study of Cataract Formation: Emory Mouse Cataract
Authors: Ozaki Yukihiro , Mizuno Aritake , Itoh Koichi , Matsushima Shingo , Iriyama Keiji
Published: July 2005

Raman spectra of Emory mouse lenses at various stages of cataract formation have been measured and compared with those of normal lenses from ICR-strain mice. The relative intensity of an OH stretching mode of lens water was considerably stronger for the Emory mouse lenses, even in a precataractous stage, suggesting that lens hydration is deeply implicated in the initiation of Emory mouse cataract. The rate of 2SH → S-S conversion, estimated from the intensity decrease of a SH stretching mode, was similar between the Emory and ICR-strain mouse lenses. Accordingly, it seems unlikely that the conversion is a predominant factor for forming large protein aggregates which lead to lens opacification. A significant change was observed for the intensity ratio of a tyrosine doublet near 840 cm−1 during the cataract development, suggesting that the strength of the hydrogen bonding of some tyrosine residues alters upon the formation of the large protein aggregates. Comparison of the Raman spectral changes observed for Emory mouse cataract with those for normal lens aging and other cataract formation leads us to the conclusion that the microenvironmental change of tyrosine residues is only one common specific feature for lens opacification.
Doppler-Free Spectroscopy Based on Phase Conjugation by Degenerate Four-Wave Mixing in Hollow Cathode Discharge
Authors: Tong William G. , Chen Dennis A.
Published: July 2005

Optical phase conjugation in the hollow cathode lamp by degnerate four-wave mixing is a novel analytical laser spectroscopic method in which a laser beam is generated as the signal beam. With the use of a demountable hollow cathode discharge cell and a continuous-wave dye laser, the signal beam is clearly visible to the naked eye when 1 µg of sodium is placed inside the cathode cavity. Since the signal beam is a time-reversed replica of the probe laser beam, highly efficient optical signal detection can be performed with minimum optical background noise. Since the signal is Doppler-free with negligible Lorentzian broadening (30 Torr discharge pressure), it provides excellent spectral resolution. Sodium D2 hyperfine lines of 3s 2S1/2 ( F' = 2) → 3p 2P3/2 ( F = 3) and 3s 2S1/2 ( F' = 1) → 3p 2P3/2 ( F = 0) were resolved. In addition to excellent spectral resolution and ease of signal detection, the technique also offers unique properties of optical phase conjugation.