bluuebunny/crossref_metadata_2025 huggingface dataset:
Pulsed-Laser Excited Differential Photothermal Deflection Spectroscopy
Authors: Bialkowski Stephen E. , Gu Xiaoyun , Poston Pete E. , Powers Linda S.
Published: June 2005

This paper describes a differential photothermal optical absorbance apparatus that uses two excitation beams at different wavelengths. A single probe beam monitors the difference in heats generated by the two wavelengths. The theory is developed for the operational principles of the apparatus, and theoretical signals are compared with those obtained with a conventional absorption spectrophotometer. The differential photothermal apparatus has a theoretical advantage over conventional spectrophotometry for samples with less than unit absorbance. Experiments are described which verify the operating principles and demonstrate the flexibility of the apparatus.
Use of an Adjustable Impact Bead in the Analysis of Solutions in Organic Solvents by Flame Atomic Absorption
Authors: Willis John B. , Sturman Barry T.
Published: June 2005

Throughput of organic solvent aerosol to the flame of an atomic absorption spectrometer may be controlled by varying the position of the impact bead relative to the nebulizer, instead of varying the solution uptake rate of the nebulizer. The usefulness of this simple technique has been demonstrated for a range of elements in three organic solvents (4-methylpentan-2-one, xylene, and a high-boiling-point iso-paraffin solvent), with air/C2H2 and N2O/C2H2 flames. It is shown that the adjustment of the impact bead alone allows the determination of high concentrations of copper and iron in lubricating oils without undue dilution of the sample and can result in significant improvements in the speed of analysis.
Infrared Study of 4- and 3-Substituted Anilines in Hexane, Carbon Tetrachloride, or Chloroform (0.5% or Less) Solutions
Authors: Nyquist R. A. , Luoma D. A. , Puehl C. W.
Published: June 2005

As the NH2 bond angle increases, both vasym NH2 and vsym. NH2 increase in frequency, and the frequency separation between vasym. NH2 and vsym. NH2 increases as the Hammett σp and σm values increase (increasing electron withdrawing power). The NH2 bond angles change with solute/solvent interaction. In CHCl3 solution IR bands are observed for two sets of vasym. NH2 and vsym. NH2 frequencies. It is suggested that this is the result of intermolecular hydrogen bonding between H2N and HCCl3 and between NH2 and Cl(HCl2)2. In CCl4 solution the intermolecular hydrogen bonding between the NH2 protons and the Cl atoms of CCl4 is stronger than between the Cl atoms of CHCl3.
Spectroscopic Investigation of Fluorescence Quenching Agents. Part II: Effect of Nitromethane on the Fluorescence Emission Behavior of Thirty-Six Alternant Benzenoid Polycyclic Aromatic Hydrocarbons
Authors: Tucker Sheryl A. , Darmodjo Hardjanti , Acree William E. , Fetzer John C. , Zander Maximilian
Published: June 2005

Nitromethane is examined as a selective quenching agent for discriminating between “alternant” versus “nonalternant” polycyclic aromatic hydrocarbons in unknown mixtures. Of the 36 benzenoid solutes studied, only dibenzo[hi,wx]heptaphene failed to obey the selective quenching rule. Also reported are new experimental fluorescence probe studies for dibenzo[de,st]pentacene, dibenzo[fg,qr]pentacene, naphtho[8,1,2hij)-hexaphene, benzo[vwx]hexaphene, benzo[1,2,3cd;4,5,6c'd‘]diperylene, dibenzo[hi,wx]heptacene, benzo[b]triphenylene, chrysense, and anthracene dissolved in nonelectrolyte solvents of varying polarity. Benzo-[vwx]hexaphene was found to exhibit probe character, as evidenced by a systematic variation in emission intensity ratio with solvent polarity.
Oxygen Permeability of Sol-Gel Coatings
Authors: Liu Hsue-Yang , Switalski Steven C. , Coltrain Bradley K. , Merkel Paul B.
Published: June 2005

Sol-gel processes are applied to prepare organic-inorganic composite coatings. The purpose of this report is to evaluate the possibility of tuning the oxygen permeability of the resulting coatings. It is proposed that if the oxygen permeability is largely controlled by the hydrophobic character and the pore sizes of membranes, then the permeability of the solgel coatings could be tuned by adjusting the composition of the organosilane precursor. The oxygen permeability is measured by the selective oxygen quenching of phosphorescent probes, such as platinum octaethylporphine (PtOEP). The application of such sol-gel coatings for optical fiber oxygen sensors will also be discussed.
Laser-Induced Fluorescence of Atoms in a Power-Modulated Inductively Coupled Plasma for Trace Detection and Diagnostic Study
Authors: Turk Gregory C.
Published: June 2005

Laser-induced fluorescence of iron atoms during the plasma-off cycle of a power-modulated inductively coupled plasma has been performed. The low plasma background emission, and absence of radio-frequency interference, 1.4 ms after complete interruption of power to the ICP, results in an excellent environment for fluorescence detection. With the use of a simple nondispersive detection system, a limit of detection of 5 µg Fe/L was achieved. The iron atom population was found to remain constant for 1.2 ms after power interruption, indicating that the chemical environment during this period is inert. A spatial profile and ICP power study were conducted as diagnostic aids for optimization of the power-modulated ICP for both fluorescence and ionization detection.
Laser-Induced Ionization of Atoms in a Power-Modulated Inductively Coupled Plasma
Authors: Turk Gregory C. , Yu Lijian , Waiters Robert L. , Travis John C.
Published: June 2005

Laser-induced ionization of atoms has been detected in a power-modulated inductively coupled plasma. The measurement is made 1.4 ms after complete interruption of the 40-MHz power to a 400-W plasma. Electrical conductivity measurements between probe electrodes in the plasma during the power-off cycle have been made, demonstrating the decay in plasma background ion/electron concentrations which makes detection of laser-induced ionization possible. Radio-frequency interference from the ICP on the ionization detection electronics is also avoided by this approach. The primary mode of laser-induced ionization was photoionization of the laser-excited atoms, i.e., resonance ionization spectroscopy (RIS). Detection limits of 80 µg Fe/L and 20 µg Ga/L were achieved.
Improved Methods for Screening of Polychlorinated Biphenyls (PCBs) Using Room-Temperature Phosphorescence
Authors: Watts W. , Pal A. , Ford L. , Miller G. H. , Vo-Dinh T. , Eastwood D. , Lidberg R.
Published: June 2005

Several methods for the improvement of room-temperature phosphorescence (RTP) analysis of polychlorinated biphenyls (PCBs) have been investigated. Two approaches that were investigated in order to detect improvements over existing methods were the second-derivative technique and synchronous scanning techniques. The effects of several phosphorescence enhancing agents were studied in order to improve the sensitivity of the RTP method. The results indicated that the RTP technique is simple and efficient for the screening of PCBs in soil samples.
Proton NMR Analysis of Octane Number for Motor Gasoline: Part IV
Authors: Ichikawa M. , Nonaka N. , Amano H. , Takada I. , Ishimori S. , Andoh H. , Kumamoto K.
Published: June 2005

Software (a program) for predicting the octane number of motor gasoline by proton magnetic resonance (PMR) spectrometry has been formulated. At the same time, a method has been studied to predict the composition of gasoline (in terms of the contents of paraffin, olefin, and aromatic compounds). The formulated program was evaluated by using it to predict the octane numbers of 31 samples of marketed summer gasoline (including 16 regular and 15 premium products), whose octane numbers and compositions were identified according to the ASTM standards. Also, the relationship between the PMR spectrum and gasoline composition was subjected to linear regression analysis by using the 31 samples whose octane numbers were calculated, and the appropriateness of the resultant regression equations was assessed. This report concerns the results of the study in which the octane numbers of the 31 samples were satisfactorily predicted by the formulated program and useful linear regression equations were obtained for the prediction of the composition of gasoline.
Novel Lightpipes for Infrared Spectroscopy
Authors: Saggese S. J. , Harrington J. A. , Sigel G. H. , Altkorn R. , Haidle R.
Published: June 2005

The fabrication and temperature-dependent mid-infrared transmission characteristics of gold-on-nickel, silver-on-nickel, silica, and sapphire hollow lightpipes are discussed. The metal tubes offer improved low-temperature transmission and more versatile fabrication methods than do conventional FT-IR lightpipes. The dielectric tubes offer extremely low loss in certain spectral regions, outstanding high-temperature performance, and, in some cases, sufficiently low cost to be considered disposable.
Coherent Anti-Stokes Raman Spectroscopy of the Stretching Vibrations of the Water Isotopomers
Authors: David D. , Strugano A. , Bar I. , Rosenwaks S.
Published: June 2005

Coherent anti-Stokes Raman spectroscopy (CARS) has been employed to study the v1 band of H2O, v1 band of DzO, and v1 and v3 bands of HOD in the gas phase at room temperature and at moderate resolution. These molecules are characterized by a complicated spectrum which is not completely rotationally resolved. A method for the deconvolution of incompletely resolved CARS spectra has been utilized, in which a Boltzmann population distribution is assumed. The calculated spectrum nearly exactly reproduces the observed spectrum and allows assignment of the rotational transitions which are observed in the spectra. All the transitions that appear in these spectra belong to the isotropic Q branches. The CARS spectra of D2O and HOD are studied here for the first time.
Electronic Tuning, Amplitude Modulation of Lasers by a Computer-Controlled Acousto-Optic Tunable Filter
Authors: Tran Chieu D. , Furlan Ricardo J.
Published: June 2005

A novel, compact, all-solid-state, computer-controlled acousto-optic tunable filter (AOTF) which has no moving parts has been developed. The filter can be successfully used not only for the rapid tuning and amplitude-modulation of the multiwavelength laser beam but also for the stabilization of the power of the diffracted beam regardless of whether it is a continuous single wavelength or a modulated multiwavelength beam. The potential applications of this filter to the spectrochemical methods of analyses are discussed.
A New Method for Feedback Stabilization of a Microwave Power Supply
Authors: Borer Matthew W. , Ensman Robert E. , Madrid Yolanda , Hieftje Gary M.
Published: June 2005

A new method has been developed for the feedback stabilization of a microwave power supply, with the intent to reduce emission noise in microwave-induced plasma atomic emission spectrometry (MIP-AES). The control method would be applicable to any microwave generator whose output power is affected by the input ac line voltage. In the feedback process, the effective line voltage is adjusted by means of a controllable inductance placed in series with a variable transformer at the input of the generator. In turn, this inductance is controlled by selecting the dc current in the primary winding of an auxiliary transformer, so the inductance in its secondary winding is altered. The long-term stability of the feedback-controlled system is verified and the range of stabilization is examined. Noise in the power output of the microwave generator is shown to be reduced at frequencies below 1.5 Hz. Although stable microwave power generation does not necessarily result in stable emission from a microwave-induced plasma source, an emission-based feedback signal is shown to improve the stability.
Historical Note on the Origins of Several Useful Infrared Techniques
Authors: Miller Foil A.
Published: June 2005

A brief discussion is presented which identifies the origins and developers of several widely used techniques in infrared spectroscopy.
A Study of Sample Surfaces and Associated Radiation until Quasi-Stationary Conditions Set in When Ferrous Samples are Arced using a High-Repetition Condensed Arc
Authors: Strasheim A. , Böhmer R. G.
Published: June 2005

Changes that occur on ferrous sample surfaces from the initiation of an arc until quasi-stationary conditions set in are addressed. For the recording of the radiation of the high-repetition condensed arc source, a sequential spectrometer is used. Enlarged burn patterns (optical and scanning electron micrographs) are depicted. The corresponding intensity ratios of the analysis line of manganese and the internal control lines of iron vs. time are also presented. Two environmental gases are used, viz., pure argon and argon plus 2% hydrogen. The appearance and growth of the hillocks are described, and a suggestion with regard to their formation is made. Evidence is presented that the main source of the radiation used for analysis comes from the central area of the eroded sample by an operative arc.
Remote-Raman Spectroscopy at Intermediate Ranges Using Low-Power cw Lasers
Authors: Angel S. M. , Kulp Thomas J. , Vess Thomas M.
Published: June 2005

A portable Raman system is described that has been developed for line-of-site spectral measurements of remotely located samples at intermediate ranges. Raman spectra were measured at distances up to 20 m with the use of a 40-mm-diameter collection optic ( f/500) and at 16.7 m with a 22-mm-diameter collection optic ( f/750). In all cases, low-power cw lasers were used with powers ranging from 23 to 100 mW. The system consists of a small f/4 image-corrected spectrograph with a liquid-nitrogen-cooled CCD detector and has been demonstrated with both an argon-ion laser, emitting at 488 nm, and an 809-nm diode laser. Applications of the system include monitoring of organic and inorganic compounds at toxic waste sites during remediation, process monitoring, and remote detection of highly toxic materials.
UV-Excited Raman and Resonance Raman Spectra of Synthetic Polymers
Authors: Chadha S. , Ghiamati E. , Manoharan R. , Nelson W. H.
Published: June 2005

High-quality, UV-excited (218–242 nm), fluorescence-free conventional Raman spectra have been generated from UV-transparent polymers such as polytetra-fluoroethylene (Teflon®), polyethylene, polypropylene, and polyoxymethylene (Delrin®). Spectra can be generated with the use of low exciting power (<1 mW), but even at low power, precautions have to be taken to prevent photo-oxidation and thermal degradation of samples. Polyvinylchloride polymers especially have been found to be prone to degradation. Weakly absorbing polymers such as nylon and polybutadiene show special promise for Raman analysis, because they exhibit significant preresonance enhancement of structurally significant modes, and because they still retain information derived from conventional Raman spectra. Strongly preresonance-enhanced ethylenic modes of polybutadiene isomers can be resolved, allowing the easy identification of cis and trans isomers. In contrast, strongly absorbing polymers such as polystyrene, polycarbonate, and polyphenolics show only intense, resonance-enhanced Raman spectra. Unfortunately, Raman spectra of these materials are limited to phenyl ring modes, and all valuable conventional Raman spectra are totally lost due to internal absorption.
Evaluation of a Frequency-Selectable Solid-State Generator for Inductively Coupled Plasma Atomic Emission Spectrometry
Authors: Brushwyler Kevin R. , Hieftje Gary M.
Published: June 2005

A solid-state rf generator was evaluated as a source for inductively coupled plasma atomic emission spectrometry (ICP-AES). The generator is controlled by a dedicated computer and is capable of sustaining analytical plasmas at either 27.12 or 40.68 MHz at powers up to 2 kW. The analytical performance of this generator was evaluated with particular emphasis on noise and stability. A quartz chimney was used to reduce audio-frequency noise in the ICP emission. Detection limits for 11 different elements and 22 different emision lines were measured when the ICP was sustained alternatively at each generator frequency.
Investigation of UO2+2 Binding Sites on Datura Innoxia Using UO2+2 Luminescence
Authors: Ke Huei-Yang David , Rayson Gary D.
Published: June 2005

A pulsed tunable dye laser has been used to obtain the emission spectra and fluorescence decay curves of solid UO2+2- Datura innoxia and a series of UO2+2-containing complexes at liquid nitrogen temperature. The decay curves of UO2+2- Datura exhibited a bi-exponential decay, suggesting that at least two different binding sites are present on the walls of nonliving D. innoxia cells. The model solutions containing carboxyl, amine, hydroxyl, phosphoryl, sulfate, and sulfonate functionalities have been utilized to identify the functionalities involving in the binding of UO2+2 to nonliving D. innoxia cell walls. Phosphoryl and dicarboxyl groups have been demonstrated to be the dominant functional groups responsible for the binding of uranyl ions on D. innoxia cell walls.
ATR/IR Spectroscopic Method for following Photo-Polymer Curing
Authors: Snyder Randy W. , Fuerniss Stephen J.
Published: June 2005

A method for examining the photo-induced polymerization of photoresists and solder masks, at the substrate/photopolymer interface, using attenuated total reflectance (ATR) and infrared spectroscopy is discussed. The method is especially useful for dry film photoresists and gives information concerning cure levels affected by exposure dose and photoresist thickness. The photoprocessing of Vacrel® 8100 series solder mask and Riston® 3100 series photoresists from Dupont are used as examples.
The Effect of Nebulizer Structure on Flame Emission
Authors: Meinhard Beth A. , Brown D. Kenneth , Meinhard James E.
Published: June 2005

The emission-producing capabilities of twelve different models of the MEINHARD™ concentric glass nebulizer were evaluated in a flame photometer in an effort to correlate nozzle geometry with emission performance. Signal intensity, stability, and internal consistency within a model were compared. Sensitivity, defined as signal intensity per mL/min sample flow, was also computed and compared. It was expected that relative performances in the flame would provide an index to relative performances in plasma or other emission excitation sources, and results would thus serve as an aid to nebulizer selection for other atomic analytical techniques including ICP. A new nebulizer, the TR-50-K2, generated signals up to 64% higher than those of the TR-30-A3 and up to 25% higher than those of the TR-30-A2 (and TR-50-C1), which produced the highest signals of currently available models.
A New Spectroscopic Technique for in situ Chemical Reaction Monitoring Using Mid-Range Infrared Optical Fibers
Authors: Moser William R. , Berard Joseph R. , Melling Peter J. , Burger Robert J.
Published: June 2005

A new versatile spectroscopic technique for chemical reaction monitoring using mid-range infrared optical fibers has recently been developed. Chalcogenide glass optical fibers were used to direct infrared radiation from an FT-IR spectrometer through ZnSe Cylindrical Internal Reflectance (CIR) crystals embedded within laboratory scale reactors. The utility of this technique for studying chemical systems was demonstrated by monitoring various stoichiometric reactions at ambient conditions. A laboratory-scale glass reactor fabricated with the capability to mount a CIR crystal was used as the reaction vessel. The ability of this system to monitor high-pressure and/or high-temperature chemical reactions was also demonstrated by studying the cobalt catalyzed hydroformylation of olefins. A stainless steel CIR reactor, slightly modified to allow for connections with optical fibers, was used for experiments ranging from 50 to 90°C and under 750 to 800 psi synthesis gas (H2/CO mixture). In all cases sufficient signal strength at the detector and adequate penetration into the bulk reaction medium was achieved, resulting in infrared spectra of high quality and resolution. Spectral scans of the reaction in progress allowed the accurate determination of the concentration of reactants and products as a function of time.
Spectroscopic Investigation of Fluorescence Quenching Agents: Effect of Nitromethane on the Fluorescence Emission Behavior of Select Cyclopenta-PAH, Aceanthrylene, and Fluorene Derivatives
Authors: Amszi Vicki L. , Cordero Yvonne , Smith Bradley , Tucker Sheryl A. , Acree William E. , Yang Chengxi , Abu-Shaqara Elias , Harvey Ronald G.
Published: June 2005

Nitromethane is examined as a selective fluorescence quenching agent for “alternant” alkyl-substituted polycyclic aromatic hydrocarbons (PAHs). Fluorescence emission behavior is reported for 11 H-benz[bc]aceanthrylene, 4 H-cyclopenta[def]phenanthrene, 4 H-cyclopenta[def]chrysene, 13 H-dibenzo[a,g]fluorene, 13 H-dibenzo[a,i]fluorene, 4 H-benzo[b]cyclopenta[mno]chrysene, 4 H-cyclopenta[pqr]picene, 7 H-dibenzo[c,g]fluorene, 9 H-benz(6,7)indeno[1,21]phenanthrene, 4 H-benzo[b]cyclopenta[jkl]triphenylene, 13 H-dibenz[bc,k]aceanthrylene, 13 H-dibenz[bc,l]aceanthrylene, and 4 H-benzo[def]cyclopenta[mno]chrysene dissolved in organic solvents of varying polarity and in acetonitrile or aqueous-acetonitrile solvent mixtures at various nitromethane concentrations. Results of these measurements show that nitromethane quenches fluorescence emission of the thirteen solutes studied, which is in complete agreement with what would be expected on the basis of the fact that all solutes are “alternant” polycyclic aromatic hydrocarbons.
Experimental Application of the Fourier Transform of the Time-Interval Probability Technique to Lifetime Measurement
Authors: Jarabo S. , Rebolledo M. A. , Calleja J.F.
Published: June 2005

In this paper the Fourier transform of the time-interval probability (FT-TIP) technique is applied to a fluorescence decay spectroscopy experiment in which a very small signal is detected. The lifetime of the 4 F9/2, level of Er3+ ions in an Er-doped glass is measured by the FT-TIP technique. It is concluded that this technique can be applied to lifetime measurement with small errors, in those experiments where standard techniques do not work well because of the small detected signal.
The Effect of Length and Diameter on the Signal-to-Noise Ratio of Evanescent Field Absorption Fiber-Optic Sensors
Authors: Colin T. B. , Yang K.-H. , Arnold M. A. , Small Gary W. , Stwalley W. C.
Published: June 2005

This paper discusses the theoretical and experimental implications of changing the length and diameter of the evanescent field sensing region of an evanescent field sensor. Particular emphasis is placed on optimizing the intensity of the evanescent field for near-infrared sensor applications. Both theoretical and experimental results show that an optimal length and diameter must be determined experimentally for each analyte system.
Polarization Measurements on Raman Scattering from Spherical Droplets
Authors: Fung K. H. , Tang I. N.
Published: June 2005

The polarization of Raman scattering from a single spherical droplet has been measured for the first time. Experiments are performed in a quadrupole cell, in which a charged liquid droplet is trapped by electro-dynamic forces. Raman scattering intensities at the 90° angle are measured for polarizations both parallel and perpendicular to that of the incident beam. The depolarization ratios thus obtained for the droplets are shown to be identical to those measured in the bulk samples. The present results indicate unequivocally that the depolarization ratio of Raman scattering is a molecular property and, as such, is not affected by the boundary conditions of the spherical droplets. Subsequently, the technique is applied to the chemical characterization of solution droplets. The presence of ion pairs in supersaturated strontium nitrate and bisulfate solutions is dramatically verified by distinct changes in the depolarization ratios.
Characterization of Solid Propellant and its Connection to Aging Phenomena
Authors: Pesce-Rodriguez R. A. , Miser C. S. , McNesby K. L. , Fifer R. A. , Kessel S. , Strauss B. D.
Published: June 2005

Solid propellant characterization has been performed with the use of three Fourier transform infrared (FT-IR) techniques: FT-IR-microscopy (FT-IR-mic), attenuated total reflectance/FT-IR (ATR/FT-IR) spectroscopy, and desorption/gas chromatography/FT-IR (D/GC/FT-IR) spectroscopy as well as thermogravimetric analysis (TGA). Emphasis was placed on examination of the content and behavior of plasticizer (bis-2,2-dinitropropyl acetal/formal, BDNPA/F) in propellant samples characterized over a 300-day period. Levels of residual solvent and other desorbable materials were examined as well. The following conclusions were made: there are significantly higher levels of both plasticizer and polymeric binder at extruded surfaces than in the interior of propellant grains; the rate of plasticizer migration in binder alone depends on the CAB:NC (cellulose acetate butyrate: nitrocellulose) ratio; and plasticizer evaporation and diffusional migration are negligible for all but one of the samples analyzed, suggesting that plasticizer is probably not responsible for observed aging phenomena. Levels of residual solvent and other minor components were observed to decrease with time under both ambient and accelerated aging conditions and may be related to aging phenomena.
T-Jump/FT-IR Spectroscopy: A New Entry into the Rapid, Isothermal Pyrolysis Chemistry of Solids and Liquids
Authors: Brill T. B. , Brush P. J. , James K. J. , Shepherd J. E. , Pfeiffer K. J.
Published: June 2005

The interface of a Pt filament pyrolysis control unit and a rapid-scan FT-IR spectrometer is described that enables the thermal decomposition of a thin film of material to be studied isothermally after heating at 2000°C/s. A model of the heat transfer of the Pt filament as a function of gas atmosphere and pressure is developed to help understand the instrument response. The control voltage of the Pt filament is highly sensitive to the thermochemistry of the thin film of sample. By simultaneously recording the control voltage and the rapid-scan IR spectra of the near-surface gas products, one learns considerable detail about chemical mechanisms relevant to combustion of a bulk material. The application of T-jump/FT-IR spectroscopy is illustrated with rapid thermolysis data for the energetic organoazide polymers azidomethyl-methyloxetane (AMMO), bis(azidomethyl)oxetane (BAMO), and glycidylazide polymer (GAP); the cyclic nitramine, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetraazacine (HMX); and the nitroaromatic 1,3,5-triamino-2,4,6-trinitrobenzene (TATB).
Optical Properties of Strongly Absorbing Media Determined by External Reflection Spectroscopy
Authors: Mielczarski J. A. , Milosevic M. , Berets S. L.
Published: June 2005

Reflection spectra of opaque samples recorded at different angles of incidence and for both polarizations were used to evaluate the optical constants. A subsequent classical oscillator fitting analysis of these spectra provided the dispersion of the refractive index and the absorption index for cuprous ethyl and butyl xanthate complexes across the mid-infrared region. The advantages of recording spectra under certain conditions are discussed.
Estimation of the Octane Number of Automobile Gasoline by Fourier Transform Infrared Absorption Spectrometry
Authors: Ichikawa M. , Nonaka N. , Takada I. , Ishimori S.
Published: June 2005

A method to estimate the octane number of automobile gasoline by Fourier transform infrared absorption spectrometry has been studied. Thirty-six kinds of regular gasoline and 38 of unleaded premium gasoline, collected from the market from winter to summer, were used as samples, and the absorptions of the C-H stretching vibration in the 3150-2800 cm−1 range of their IR spectra were used to plot each sample in a two-dimensional space, followed by an attempt to graphically classify the two broad types. On the other hand, the IR spectra of other samples with known octane numbers (88.0 to 100.8 in octane number) and, on that basis, samples with known octane numbers, were mapped into the space in which the regular gasolines and the premium gasolines were classified to determine their dispersion in this space. A further attempt was made to formulate a linear regression equation for use in octane number estimation. As a result, it was found that regular and premium gasolines could be definitely distinguished from each other according to the C-H stretching vibration in the 3150-2800 cm−1 near-infrared range, and that the octane number could be visually estimated. The formulation of a satisfactory regression equation was also made possible. These results are reported.
Near-Infrared Raman Spectroscopy Using CCD Detection and a Semiconductor Bandgap Filter for Rayleigh Line Rejection
Authors: Schulte Alfons
Published: June 2005

A novel application of a tuneable Ti: sapphire laser and a CdTe Rayleigh line rejection filter for near-infrared Raman spectroscopy employing a single grating spectrograph and multichannel detection is demonstrated. Raman spectra of liquid, solid, and photobiological samples have been measured within 75 cm−1 of the exciting laser line. At excitation wavelengths between 790 and 850 nm, a significant improvement in sensitivity over that for present Fourier transform Raman techniques has been obtained.
Comparison of the Vibrational Spectra and Assignments for α-Syndiotactic, β-Syndiotactic, Isotactic, and Atactic Polystyrene and Toluene
Authors: Nyquist R. A. , Putzig C. L. , Leugers M. A. , McLachlan R. D. , Thill B.
Published: June 2005

Vibrational assignments for α-syndiotactic polystyrene are made with the use of parallel and perpendicular polarization of uniaxially oriented film, and by comparison of vibrational data and assignments for toluene and atactic and isotactic polystyrene. Vibrational assignments are given for a cast film of β-syndiotactic polystyrene. These assignments are made by comparison with assignments for toluene and isotactic and atactic polystyrene and partial assignments for α- and β-syndiotactic polystyrene. Some of our assignments suggest that the crystal structure of α-SPS may not be isomorphous with C2 r symmetry.
Determination of the Effective Depth for Double-Fiber Fluorometric Sensors
Authors: Zhu Zhong Yuan , Yappert M. Cecilia
Published: June 2005

The relationship between the relative fluorescence signal excited and collected with a double-fiber optic sensor and the sample depth has been investigated. The complexity of the analytical expressions for the relative fluorescence signal and the effective depth was reduced by deriving a set of semi-empirical equations which can be evaluated in a simple fashion. These expressions take into account the configuration of the sensor, i.e., fiber diameter, acceptance angle, and separation between fibers. The expressions were tested with the use of double-fiber sensors with different diameters and separations between fibers. The reduction of the effective depth in solutions with significant absorbance was evaluated.
Changes in the Photophysical Properties with Heavy Atoms and the Effects of Modulus for 4-Phenylphenol in Solid-Matrix Luminescence
Authors: Purdy Barbara B. , Hurtubise Robert J.
Published: June 2005

Fluorescence and phosphorescence quantum yields and fluorescence and phosphorescence lifetimes were obtained for 4-phenylphenol adsorbed on filter paper with either NaCl, NaBr, or Nal at 296 and 93 K. From these data several photophysical parameters were calculated and compared. In general, the photophysical data showed that the heavy-atom effect was operative, with NaI showing the greatest effect. However, NaBr at 93 K showed both the heavy-atom effect and another effect which was particular to NaBr. For 4-phenylphenol with NaI, very little increase occurred for the phosphorescence quantum yield from 296 to 93 K, which indicated that almost maximum phosphorescence quantum yield was achieved at room temperature for 4-phenylphenol with NaI present. The increase in phosphorescence lifetime for 4-phenylphenol from room temperature to low temperature was shown to be related to the increase in the Young's modulus of filter paper as the temperature was lowered. Calculated phosphorescence lifetimes at room temperature and at low temperature with equations that included Young's modulus values agreed very well with experimental lifetime values.
Formulas for the Analysis of the Surface SFG Spectrum and Transformation Coefficients of Cartesian SFG Tensor Components
Authors: Hirose Chiaki , Akamatsu Naotoshi , Domen Kazunari
Published: June 2005

Comprehensive expressions have been presented to facilitate the analysis of the surface sum-frequency generation (SFG) spectrum. The electric field components of the SFG beam for a given experimental setup have been related via appropriately defined Fresnel coefficients to the nonlinear source polarization, which in turn has been related to the electric fields of exciting visible and infrared beams through the macroscopic SFG susceptibility tensor. The coefficients of transformation have been given to relate the laboratory-fixed Cartesian components of the SFG tensor to the components described in a surface-fixed axis system. The tensor components have been further related to the components of the microscopic hyperpolarizability tensor of surface species, and the explicit expressions (in terms of the Euler angles defining molecular orientation) of the transformation coefficients are presented to describe the Cartesian tensor components described in a surface-fixed axis system by the molecule-fixed components.
Vibrational Study of Alkyl Isocyanates in Solution
Authors: Nyquist Richard A. , Luoma Davin A. , Putzig Curt L.
Published: June 2005

The vasym. NCO frequencies for alkyl isocyanates occur at higher frequency in CHCl3 solution than in CCl4 solution. With the exception of tert-butyl isocyanate, the vasym. NCO mode increases in frequency as the mole % CHCl3/CCl4 increases. The vasym. NCO mode for tert-butyl analog increases in frequency up to a certain mole % CHCl3/CCl4 and then vasym. NCO decreases in frequency. The vasym. NCO mode for n-butyl isocyanate occurs at an exceptionally high frequency for the alkyl isocyanate studied, and this result is explained in terms of the formation of a pseudo six-membered intermolecular hydrogen-bonded ring. Inductive and steric factors also influence the type and form of solvent/solute complexes formed vs. mole % CHCl3/CCl4 as determined by study of the vasym. NCC frequencies. In general, the vasym. NCO and the vsym. NCO modes for alky isocyanates decrease in frequency as the number of hydrogen atoms on the α-carbon atom of the alkyl group decreases from 3, to 2, to 1, to 0. Some of the alkyl isocyanates exhibit two significant IR bands in the region expected for vasym. NCO, and the methyl analog exhibits three significant bands in this region of the spectrum. These IR bands are the result of vasym. NCO in Fermi resonance with combination tones, and the unperturbed frequencies have been calculated with the use of the recorded data.
Enzyme-Linked Immunoassays Using Nanosecond Fluorometric Detection
Authors: Azimi Nooshin T. , Wen Fujiang , Lister Richard M. , Chen Dennis A. , Lytle Fred E.
Published: June 2005

Nanosecond temporal resolution is combined with an enzyme-linked immunosorbent assay (ELISA) to improve the lower limit of detection for a plant virus, brome mosaic virus. The method uses alkaline phosphatase as the enzyme link and β-naphthyl phosphate as the substrate. Enzymatic activity produces the highly fluorescent tag β-naphthol. The 8.9-ns lifetime of the tag allows temporal discrimination against the assay blank, providing a 64× improvement in the detection limit as compared to a steady-state measurement, and a ∼4100× improvement over a standard ELISA method incorporating the chromogenic substrate p-nitrophenyl phosphate.
Determination of Effective Depth and Equivalent Pathlength for a Single-Fiber Fluorometric Sensor
Authors: Zhu Zhong Yuan , Yappert M. Cecilia
Published: June 2005

The relationship between sample depth and the corresponding fluorescence signal excited and collected with a single-fiber fluorometric optical sensor has been theoretically derived. The effective depth, zeff, is defined as the sample depth from which 90% of the total fluorescence signal originates. This parameter can be theoretically predicted as a function of the fiber radius, r0, the acceptance angle, α, and the sample absorbance. For solutions of negligible absorbance, the effective depth is zeff = 9 r0 tan−1α. The theoretical expressions have been experimentally tested with the use of 100- and 200-μm-core fibers and Rhodamine 6G solutions of different absorbances.
Evaluation of an Improved Burner Design for a Flame Infrared Emission (FIRE) Gas Chromatography Detector
Authors: Zhang Yunke , Busch Kenneth W. , Busch Marianna A.
Published: June 2005

Flame infrared emission (FIRE) measurements made at 4.4 μm have shown that changes in burner design have improved the sensitivity of the FIRE radiometer by approximately 1-1.5 orders of magnitude. The new burner consists of two concentric, stainless steel tubes. Air is introduced through the outer tube, while a mixture of GC effluent and hydrogen gas is introduced through an inner capillary tube. When the burner is used as a detector for gas chromatography (GC), optimization parameters were found to be the same for a variety of compounds, GC columns (packed and capillary), and injection volumes (0.1–2.0 μL). Since less hydrogen was required to produce a stable flame, flame background emission was greatly reduced, background subtraction was no longer required, and instrumental complexity was considerably reduced. The new FIRE-GC detector could be used in conjunction with capillary columns, thus permitting improved separation of more complex mixtures. A conservative estimate of detection limits (2 σ), obtained with a mixture of benzene, butanone, 1-chloro-3-methylbutane, and methyl acetate, indicated that the new FIRE-GC detector had an average detection limit of 4.5 ± 1.3 ng s−1 in terms of carbon. Response ( μmoles of carbon) was linear over the entire range of concentrations tested, giving an estimated linear dynamic range of at least 3.4 orders of magnitude. The utility of the new FIRE-GC detector was demonstrated by an application involving the separation of a synthetic mixture of 16 compounds on a 15-m silica capillary column under programmed temperature conditions. The new burner responded well to halogenated, nonhalogenated, and aromatic compounds with boiling points in a range from 36 to 152°C.
Spark Ablation of Solid Samples for Analysis by Inductively Coupled Plasma-Mass Spectrometry
Authors: Ivanovic Kristine A. , Coleman David M. , Kunz Frank W. , Schuetzle Dennis
Published: June 2005

High-voltage spark ablation is used for the direct analysis of solid samples using ICP-MS detection. Separation of sample vaporization, excitation, and detection phenomena allows each event to be optimized independently, thereby facilitating (among other things) enhanced sampling efficiency. Qualitative evaluation of elemental constituents is demonstrated. A direct linear relationship between electron multiplier counts and concentration was observed for trace elements (ranging from 0.75 to 125 ppm) in a series of “pure” copper standards. It is significant that neither concentration normalization nor internal standardization procedures were required. Sample uptake and clean-out times are minimal. This technique can be applied for the direct determination of conductive samples (or materials that can be converted into conductive form) with little or no sample preparation. For such samples, spark ablation could serve as an alternative to laser sampling in cases where larger sampling sites (∼1–2 mm) can be tolerated. In contrast, this technique uses inexpensive instrumentation, is simple to operate, and shows good accuracy and precision, even in prototype form.
Analysis of Nontransparent Polymers: Mixture Design, Second-Derivative Attenuated Total Internal Reflectance FT-IR, and Multivariate Calibration
Authors: Toft Jostein , Kvalheim Olav M. , Karstang Terje V. , Christy Alfred A. , Kleveland Karstein , Henriksen Arne
Published: June 2005

The composition of nontransparent polymers has been predicted from the fingerprint region in the mid-IR. The polymers were analyzed by the Horizontal Attenuated Total internal Reflection (HATR) FT-IR technique. The polymers were blends of three different master batches: (1) a polymer of ethylene with carbon black, (2) a co-polymer of ethylene and propylene monomers, and (3) an ethylene-propylene-diene elastomer. A calibration set was defined by use of mixture design. Partial least-squares (PIS) regression was used to calculate models for prediction of the relative concentrations of each master batch (one at a time). Second-derivated IR profiles normalized to 100% were used as predictive variables. Two alternative criteria were compared for optimizing the predictive ability of the calibration models: (1) squared prediction error of all the calibration samples, and (2) prediction error of replicated calibration samples of the centerpoint in the design only. The latter criterion turned out to be the more useful for the purpose of this study. This is because the centerpoint represents the target sample of the blending process. The one-component PLS models, suggested by the latter optimization criterion, gave predictions within 1% of the stated relative concentrations and with standard deviations from 0.5 to 1.3% for all three master batches.
Kramers-Kronig Calculation of the Grazing Angle Reflection Spectrum of Barrier Oxide Layer on Aluminum
Authors: Nishikida Koichi , Hannah R. W.
Published: June 2005

The nature of the grazing angle reflection spectrum of the thin oxide layer formed on the surface of aluminum was examined by Kramers-Kronig calculations. It was confirmed that the 960-cm−1 peak seen in the grazing angle reflection spectrum corresponds to the absorption band at 738 cm−1 of a low-temperature transition alumina such as γ-Al2O3. The large frequency shift toward higher frequencies is explained in terms of the product between the real and imaginary parts of the refractive index of the oxide. Simulation using the Kramers-Kronig calculation showed, in addition, a very weak structure at about 700 cm−1 in the grazing angle reflection spectrum, which was attributed to a peak shifted from the 590-cm−1 absorption peak of γ-Al2O3.
Surface-Enhanced Raman Study of Benzylpenicillin
Authors: Reipa V. , Horvath J. J.
Published: June 2005

The surface-enhanced Raman spectra (SERS) of benzylpenicillin on electrochemically roughened Ag electrodes were investigated. Spectral assignments were carried out. Comparison with powder Raman spectra demonstrated that the benzene ring is in a vertical position relative to the surface. The molecule is bonded to the silver surface through the carboxylate group and the tertiary nitrogen of the beta-lactam ring, resulting in formation of a bidentate surface complex. Evidence of partial benzylpenicillin hydrolysis into 6-aminopenicillanic acid and phenylacetic acid on the surface of the electrode is presented. No indication of electrochemical reactions was observed in the potential range from −1.2 to +0.3 V.
Collective Spontaneous Emission in CS2
Authors: Liou H. T. , Fain B. , Lin S. H.
Published: June 2005

The collective emission of the CS2 vapor at 400 mTorr in a 115-cm cell was observed, when the system was irradiated with a 1 mj pulsed laser of 20 ns duration at 343.57 nm. Dicke's theory of superradiance was applied to interpret the experimental data.
Anomalous Pressure Dependence of Infrared Spectra Due to the Combination of Collisional Broadening and Instrument Resolution
Authors: Maricq M. Matti , Szente Joseph J.
Published: June 2005

The combination of collisional line broadening and limited instrumental resolution can have peculiar and unexpected effects on the intensities of infrared spectra. An illustrative example is provided by the series of Q branches in the v7 band of ethane. Conventional FT-IR spectra, with a resolution of ∼0.25 cm−1, show a dramatic increase in the absorbance of these branches as a function of increasing N2 partial pressure, an effect which could be construed as collisional narrowing. In contrast, high-resolution diode laser spectroscopy reveals a monotonie increase in branch width (0.14 cm−1/atm), and a concomitant decrease in intensity, as the N2 pressure is raised. The present work shows that absorption measurement of the inherently very narrow ethane Q branches with limited instrumental resolution and collisional line broadening conspire to give the appearance that the absorbance increases with N2 pressure. This effect in general, as well as its implications for the use of FT-IR spectroscopy to measure molecular concentrations in gaseous mixtures, is discussed.
On-Line Detection in Slab Gel Electrophoresis Using Thermal Lens Spectrophotometry
Authors: Thompson Michelle A. , Ford John C. , Long George R.
Published: June 2005

Thermal lens spectrophotometry was used to detect hemoglobin and cytochrome c within an acrylamide gel matrix both during electrophoresis and in static experiments in which each protein was incorporated in the matrix during polymerization. For cytochrome c, the detection limit was 0.02 mg/mL for static experiments (approximately 0.5 ng in the laser beam volume), while a detection limit of 180 ng (5 ng in the beam volume) was found for electrophoresis runs.
Effect of Sample Injection Modes on Residue Deposits in Graphite Furnace Atomic Absorption
Authors: Howell A. G. , Koirtyohann S. R.
Published: June 2005

Two modes of liquid sample deposition into the graphite furnace were studied: injection of a single droplet by micropipet and injection of an aerosol spray. The deposition modes were compared with respect to structure of the deposit, corrosive effects on the graphite, and analytical data for Se with Ni matrix modification. Examination of the deposits by scanning electron microscopy revealed that, contrary to previous assumptions, deposition of an aerosol resulted in solids with larger crystals than that produced by micropipet injection (under the conditions used in the study). Corrosion of the surface of the graphite tube was more severe in general with aerosol injection. Analytical data demonstrated that deposits with larger crystals resulting from aerosol injection produced increased sensitivity for Se under the conditions of the study.
Estimating Detection Limits in Ultratrace Analysis. Part III: Monitoring Atoms and Molecules with Laser-Induced Fluorescence
Authors: Stevenson Stopher L. , Winefordner James D.
Published: June 2005

Laser spectroscopic methods which are sensitive enough to detect single atoms or molecules are termed single-atom detection (SAD) techniques. The detection theory of SAD methods, presented in the second paper in this series and summarized here, allows for the evaluation and comparison of these techniques. In this paper, SAD theory is applied to one task in particular: monitoring analyte atoms or molecules as they flow through a continuous-wave laser beam using fluorescence detection (CW-LIF). Several possible signal-processing methods are described and evaluated through the use of SAD theory and Monte Carlo simulations. The relative merits of these methods for SAD by CW-LIF are illustrated.
A Raman Study of the Isomers and Dimer of Hydrogen Sulfite Ion
Authors: Littlejohn David , Walton Susan A. , Chang Shih-Ger
Published: June 2005

Raman spectra of aqueous solutions of hydrogen sulfite ion (SHO3−) were collected over temperatures of 275 to 340 K. The change in peak intensities with temperature was used to assign peaks to the hydrogen sulfite isomers. The HOSO2− isomer has a peak at 1023 cm−1 and the HSO3− isomer has a peak at 1052 cm−1. The relative strengths of the peaks were determined and used to measure the equilibrium quotients for hydrogen sulfite ion.

Q1 = [HOSO2−]/[HSO3−]

Q2 = [S2O52-]/[SHO3−]2

No evidence was found for a hydrogen sulfite dimer other than disulfite ion, S2O52-.