bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Transient Molecular Absorption in a Graphite Furnace by Laser-Induced Plasmas
Authors: Majidi Vahid , Ratliff Judy , Owens Mitchell
Published: July 2005

The transient molecular species that are produced in electrothermal atomizers are probed by backlighting the furnace with continuum emission from laser-induced plasmas. Laser plasmas provide a stable and strong continuum spectrum in the UV region for molecular absorption studies. These plasma sources exhibit a substantial improvement in UV absorption measurement over the more conventional sources, permitting good time resolution. The molecular absorption spectrum from 190 to 320 nm for NaI, NaCl, and KH2PO4 are illustrated. The temporal and spectral resolution of this instrument are 100 ms and 0.2 nm, respectively.
Multivariate Calibration of a Photodiode Array Spectrometer for Atomic Emission Spectroscopy
Authors: Glick Mark , Brushwyler Kevin R. , Hieftje Gary M.
Published: July 2005

Multiple linear regression with stepwise selection of variables is used to calibrate a photodiode array spectrometer for inductively coupled plasma-atomic emission spectrometry. The spectrometer uses a preliminary wavelength selector and an echelle grating (without an order-sorting prism) to provide high-resolution information over a wide wavelength range. Chemical systems exhibiting various obstacles to quantitation, including spectral-line overlap, interference due to broadened spectral lines, and stray light from a line of high intensity, are calibrated successfully with a multivariate technique. Sample sets used for calibration are constructed with the use of simplex lattice designs, and the method of cross-validation is used to assess the predictive performance of the calibration models. Conventional univariate calibration using spectral peak areas is performed for comparison.
Identification of Several Wavelengths Useful for ICP That are Incorrectly Listed in the Literature
Authors: Grosser Zoe A. , Collins John B.
Published: July 2005

A previously characterized sequential scanning ICP spectrometer with nominal resolution of 0.009 nm, FWHM, for a 3600-line/mm grating and 0.018 nm for a 1800-line/mm grating is used to examine wavelength positions. Five atomic lines believed to have been reported in error in the literature are identified. Alternative values for each wavelength are suggested.
A Calcium-Selective Optrode Based on the Fluorescence of Dansylated Troponin
Authors: Eckert-Tilotta S. E. , Scouten W. H. , Hines John
Published: July 2005

Troponin C (TnC) is covalently labeled with a fluorescent probe molecule dansylaziridine and immobilized on polyethyleneimine-impregnated cellulose. An optrode is constructed by attaching the treated cellulose membrane to the distal end of a bifurcated fiber-optic cable. Because fluorescence is enhanced as Ca+2 binds with the immobilized dansylated troponin (TnCDANZ), this system can be used as a calcium sensor for monitoring plasma Ca+2 levels.
Photoacoustic FT-IR Study on Keratin Chemically Bound on the Surface of Silica Gel Particles
Authors: Nishio Etsuo , Abe Ikuo , Ikuta Nobuo , Koga Joichi , Okabayashi Hirofumi , Nishikida Koichi
Published: July 2005

The conformation of keratin chemically bound to the surface of silica gel particles has been investigated by means of photoacoustic Fourier transform infrared (PA/FT-IR) spectroscopy. On the basis of the peak positions of the amide I and amide II bands, it is concluded that the keratin thin layer assumes the native α-helix form. It is also noted that the PA/FT-IR method is the only feasible method for observing the IR spectra of the very thin layer of keratin coating on the silica gel particles. The diffuse reflectance technique failed to provide any information on keratin, because of the strong spectral artifact due to the specular reflection at the surface of the silica gel.
New Organic Scintillators with Large Stokes Shifts
Authors: D'Ambrosio C. , Leutz H. , Taufer M. , GÜsten H.
Published: July 2005

Four new scintillators were synthesized on the basis of l-phenyl-3-mesityl-2-pyrazoline in order to obtain a series of dopants with large Stokes shifts for application in ionizing particle counting. Absorption and emission spectra, light yield, quantum efficiency, decadic extinction coefficients, and absorption lengths of their toluene solutions were measured and compared to results for p-terphenyl (+ POPOP) and 3-HF, which have already been applied for particle detection.
Spatial and Temporal Distributions of Large Molecules in Plumes Generated by Laser Desorption
Authors: Kimbrell Sandra M. , Yeung Edward S.
Published: July 2005

To understand the laser desorption process for large molecules, one needs information about the neutral species that are formed. For absorbing dye molecules, this can be accomplished by imaging the plume over its lifetime of a few milliseconds with a probe laser. Using this novel technique, we have investigated the dependence of the formation of neutral gas-phase dye molecules on vaporization laser power. It is clear that destruction of the chromophore (fragmentation) occurs even at low vaporization powers.
Measurement of Trace Silanol in Siloxanes by IR Spectroscopy
Authors: Lipp Elmer D.
Published: July 2005

Two novel approaches for the measurement of trace SiOH moieties in siloxane polymers by IR spectroscopy are described. Both methods are based on the idea of selective spectral modification of SiOH absorbance bands so that the silanol absorbance bands can be isolated in the presence of much larger, overlapping background absorbances. Modification of the SiOH groups is made to occur either through H-bonding using mixed solvent systems or through deuteration resulting from isotope exchange in the presence of excess D2O. Both techniques have high specificity for SiOH groups over other portions of the molecules and produce only minimal changes in the IR absorbances due to non-silanol moieties. Subtraction of a modified sample spectrum from an unmodified spectrum then allows the SiOH absorbances to be isolated and quantitatively measured to low concentrations. These techniques allow one to circumvent a major limitation of IR spectroscopy for trace analysis, namely, the need to rely on a separate reference material for the removal of interfering background absorbances. Of the two methods described in this paper, the deuteration approach is superior in terms of ease and sensitivity. Measurements can be made down to 10 ppm (wt OH/wt sample), which is close to the noise level of the spectral measurement.
A Surface Spectroscopic and Wettability Study of a Segmented Block Copolymer Poly(Etherurethane)
Authors: Vargo Terrence G. , Hook Daniel J. , Gardella Joseph A. , Eberhardt Mary A. , Meyer Anne E. , Baier Robert E.
Published: July 2005

In this study, a multitechnique surface analytical approach is used to provide comprehensive surface molecular, structural, and thermodynamic information of a segmented Poly(etherurethane) (PEU) block copolymer (Texin-985). Through sample preparation methods described in this paper, a clean stable PEU material is provided. Subsequent analysis employing Electron Spectroscopy for Chemical Analysis (ESCA), Attenuated Total Reflectance Fourier Transform Infrared (ATR/FT-IR), and Comprehensive Wettability Profiling provides a comprehensive molecular structure of the topmost interfacial region, ranging through a bulk analysis probing depths in the micron range. Also featured in this paper are results obtained through the implementation of a higher-energy x-radiation source for ESCA analysis. Through the use of angle-dependent ESCA utilizing Mg K α x-radiation, used in conjunction with a Ti K α x-radiation source, a hard- and soft-component depth profile expanded from a conventional profile of ∼20 Å to 100 Å (using a Mg anode source) to ∼20 Å to 200 Å is obtained. Due to the greater depth of analysis, we also obtain atomic ratios (using calculated sensitivity factors) which are closer to true bulk atomic percentages of Texin-985 (PEU).
Characterization of a Laser Plasma in a Pulsed Magnetic Field. Part I: Spatially Resolved Emission Studies
Authors: Mason Kelly J. , Goldberg Joel M.
Published: July 2005

The effect of a pulsed magnetic field on spatially resolved emission from a laser plasma at atmospheric pressure was investigated. The pulsed magnetic field, produced by capacitive electrical discharge through a specially designed solenoid, was oriented normal to the laser axis. Temporally integrated emission enhancements due to the magnetic field were found to be most significant when the plasma was formed about 1 mm below the magnetic field axis. The degree of confinement of the plasma increased with magnetic field strength—these studies utilized the maximum magnetic field attainable with this system that did not jeopardize the structural integrity of the solenoid (∼85 kG). Laterally resolved emission characteristics (observed both along and normal to the magnetic field axis) demonstrated significant radial compression and axial expansion of the laser plasma. These effects are explainable by JxB or fluid magnetic pressure interactions. Further deconvolution of dynamic magnetic field effects on plasma atomization/excitation/ionization characteristics require spatially and temporally resolved emission and absorption studies.
Thermo-Optical Absorption Detection in 25-μm-i.d. Capillaries: Capillary Electrophoresis of Dansyl-Amino Acids Mixtures
Authors: Bruno Alfredo E. , Paulus Aran , Bornhop Darryl J.
Published: July 2005

An intensity-modulated 257-nm pump laser beam is used to induce refractive index changes inside of a capillary tube employed as an on-line detection system for capillary electrophoresis. These refractive index changes inside the capillary are monitored by demodulating the periodic lateral shifts of the interference fringes, generated by a probe laser beam oscillating at 633 nm, with a phase-sensitive amplifier. The use of capillaries with an internal diameter of 25 μm results in a twofold benefit in electrophoretic separations in conjunction with thermo-optical detection. The pumped heat is efficiently quenched at the capillary wall, and high electrical fields can be applied along the separation tube. The combination of both effects leads to highly efficient separations and fast modulations of the pump source. This is demonstrated by the separation of a test mixture of three dansylated amino acids in less than two minutes. Only 350-pg amounts of total sample are injected onto the column, and the detection volume is less than 10 pL.
Concomitant Effects in a Magnetron Rotating Direct-Current Arc Plasma with Graphite-Furnace Sample Introduction
Authors: Slinkman David , Sacks Richard
Published: July 2005

The effects of the concomitant species Li, K, and Zn on analyte emission line intensities from a magnetron rotating direct-current arc plasma are described. The arc plasma has the form of a radial current sheet which completely covers the end of the graphite anode. The sample vapor from a graphite furnace is forced to pass through the current sheet. The presence of an easily ionized element (EIE) does not significantly alter the sample/plasma interaction. Large increases in emission intensities from both neutral-atom and ion lines of the analyte are observed in the presence of K or Li. This is probably the result of increased electron density in the plasma tail flame. Concomitant species which are not easily ionized have a smaller effect on analyte emission intensities, and either intensity enhancement or suppression effects are observed. Significantly lower detection limits are obtained in the presence of an EIE.
Gated Peak Integration versus Peak Detection in White Noise
Authors: Voigtman Edward
Published: July 2005

The optimum gated integration windows for a variety of common peak shapes in stationary, white noise are derived by means of simple linear systems theory. Optimum windows are found to provide signal-to-noise ratios less than 10% lower than the matched filter results. The confusion between peak detection and narrow gate window integration is discussed, and it is demonstrated that both are inferior to optimum gated integration. It is also shown that the matched filter result is the appropriate benchmark against which proposed new detection techniques should be compared.
Comparison of Photoacoustic, Attenuated Total Reflection, and Transmission Infrared Spectra of Crystalline Organoiron(II) Carbonyl Complexes
Authors: Butler Ian S. , Li Hongqi , Gao Jian Ping
Published: July 2005

Photoacoustic (PA), attenuated total reflection (ATR), and transmission IR spectra of the solid organoiron(II) complexes, CpFe(CO)2I and [ CpFe(CO)2 R]BF4 ( Cp = η5-C5H5; R = C2H4, CH2CMe2, 3-Me-thiophene), have been recorded at room temperature in the near-, mid-, and far-IR regions. Vibrational assignments are proposed for most of the observed bands including those in the binary overtone and combination regions. The relative intensities of the peaks in the different spectral regions indicate that PAS is the most sensitive in the near-IR region, affording good information on binary vCO and vCH overtones and combinations, while ATR spectroscopy leads to the most intense peaks in the far-IR region.
Optical Radiation Efficiency of Surface-Wave-Produced Plasmas as Compared to DC Positive Columns
Authors: Margot J. , Moisan M. , Ricard A.
Published: July 2005

The influence of the high-frequency (HF) field (200-900 MHz), gas pressure (0.05–1.0 Torr) and plasma density on the radial density distribution of excited atoms in a cylindrical HF sustained discharge of the surface-wave type is experimentally examined through optical emission spectroscopy, with the use of a tomography technique. These results illustrate the role of the radial inhomogeneity of the wave electric field intensity (the so-called skin effect) on the radial density distributions of excited atoms. This set of data, completed by similar measurements for the positive column of a dc discharge, is further used to investigate the optical radiation efficiency as a function of the field frequency. It shows that there exist discharge conditions for which the surface-wave plasma is more efficient, the optimum frequency then being around 200 MHz. The explanation for such a behavior calls on the frequency dependence of both the radial density distribution of the excited atoms and the electron energy distribution function (EEDF), the latter determining how the power absorbed from the HF electric field is shared between ionization and excitation processes. These various results are compared with the self-consistent model developed for surface-wave discharges in argon by Ferreira and co-workers.
Indirect Determination of Phosphate, Silicate, and Arsenate by HPLC-AES
Authors: Pomeroy Robert S. , Baker Mark E. , Kolczynski Jeffrey D. , Denton M. Bonner
Published: July 2005

The indirect determination of phosphate, silicate, and arsenate is performed by separation of their heteropoly acids by using ion-pair reverse-phase HPLC (IP-RPHPLC) and monitoring the molybdenum emission from a DCP with an echelle spectrometer and a charge-injection device (CID) detector. Limits of detection found for phosphate, silicate, and arsenate are 26, 31, and 52 ng/mL, respectively. The detection limit for arsenate is slightly degraded due to its proximity to the excess molybdate peak. These results represent an improvement in the determination for these nonmetals over results for direct aspiration into an emission source and show excellent linearity over three orders of magnitude.
Polycyclic Aromatic Hydrocarbon Solute Probes. Part VIII: Evaluation of Additional Naphthacene and Perylene Derivatives as Possible Solvent Polarity Probe Molecules
Authors: Tucker Sheryl A. , Teng I.-Lih , Acree William E. , Fetzer John C.
Published: July 2005

Fluorescence emission spectra are reported for phenanthro[5,4,3,2efghi]perylene, dibenzo[cd,k]naphtho[8,1,2fghi]perylene, benzo[b]peryiene, dibenzo[e,ghi]perylene, and benzo[a]naphtho[8,1,2cde]-naphthacene dissolved in various organic solvents. Results of these measurements are used to screen PAHs for potential solvent polarity behavior. Of the five PAHs studied, only phenanthro[5,4,3,2efghi]perylene exhibited probe behavior, as evidenced by selective emission intensity enhancement of band I with increasing solvent polarity.
The Investigation of a 13-mm Torch for Use in Inductively Coupled Plasma-Mass Spectrometry
Authors: Ross Barbara S. , Yang Pengyuan , Hieftje Gary M.
Published: July 2005

A 13-mm torch is evaluated for use in inductively coupled plasma-mass spectrometry (ICP-MS). With this system, an analytically useful plasma can be supported at 1.35 kW applied rf power and 9.35 L/min total argon flow. The effect of operating parameters (nebulizer flow rate, rf power, sampling depth, and ion-lens voltages) on analyte ion signals was examined, also. The optimal nebulizer-gas flow rate, sampling depth, and power for the 13-mm torch were found to be comparable to those used for the standard (18-mm) torch. Similar trends were seen between the two systems when these parameters were varied. Under optimal operating conditions, the 13-mm torch was found to produce comparable sensitivities, oxide-ion ratios, and doubly charged ion ratios. The most significant difference exhibited between the two torches was the independence of the doubly charged ion ratio on plasma parameter settings for the 13-mm torch.
Eigenvector-Based Spectral Enhancement of Nuclear Magnetic Resonance Profiles of Small Volumes from Human Brain Tissue
Authors: Abousleman G. P. , Jordan R. , Griffey R. H.
Published: July 2005

Nuclear Magnetic Resonance (NMR) spectroscopy is a low-energy technique which suffers from poor inherent signal-to-noise ratio (SNR). In a clinical setting, it is often desirable to study small regions of tissue in patients to aid in the detection and diagnosis of disease states. Analysis of the smaller regions, however, degrades the SNR further and renders conventional spectral estimation techniques such as the discrete Fourier transform useless. We demonstrate the utility of two complex eigenvector-based algorithms, Multiple Signal Classification (MUSIC) and Minimum Norm, in the detection of resonances within small sample volumes. The results indicate that these methods are clearly superior to Fourier transform-based techniques currently available on clinical NMR scanners.
A Miniature Electrical Furnace as an Excitation Source for Low-Temperature, Gas-Phase, Infrared Emission Spectroscopy
Authors: Tilotta David C. , Busch Marianna A. , Busch Kenneth W.
Published: July 2005

The analytical utility of low-temperature, gas-phase infrared emission spectroscopy is studied with the use of a specially designed miniature electrical furnace. This furnace, designed to minimize blackbody radiation from the source itself, was capable of operating between 100 and 1000°C and producing infrared emission from parent analyte molecules, as opposed to their terminal combustion products, such as CO2 and H2O. The low-temperature, infrared emission spectra of nitrous oxide (225°C) and methyl benzoate (250 and 700°C) are reported, and the feasibility of determining ethanol in gasohol is evaluated with the use of the alcohol C-O stretching vibration (observed at 1070 cm−1 in emission). The detection limit for ethanol in gasohol at 202°C was found to be 0.124% v/v, and the relative standard deviation of eight single-scan determinations of ethanol in a 10% v/v gasohol blend was found to be 4.01%. Some of the advantages and limitations associated with analytical, low-temperature, gas-phase, infrared emission spectroscopy are discussed and compared with results obtained with a hydrogen/air flame as the excitation source.
Static Secondary Ion Mass Spectrometry and X-Ray Photoelectron Spectroscopy of Deuterium- and Methyl-Substituted Polystyrene
Authors: Chilkoti Ashutosh , Castner David G. , Ratner Buddy D.
Published: July 2005

Denteration in polystyrene (PS) and the differences between PS, poly(4-methyl styrene) (P4MS), and poly( α-methyl styrene) (PAMS) were examined with static secondary ion mass spectrometry (SIMS) and x-ray photoelectron spectroscopy (XPS). Only the effects of methyl substitution could be distinguished by XPS on the basis of the valence band spectra. However, it was demonstrated that both deuterium and methyl substitution effects could be clearly distinguished by static SIMS. Additionally, the effect of these substitutions could be explained in a manner analogous to that used for electron impact (EI) mass spectrometry. By the use of deuterium-labeled polymers, H scrambling was observed during secondary ion formation from PS. The validity of previously postulated secondary ion structures was confirmed on the basis of the fragmentation patterns of both the deuterium and methyl-substituted PS.
A Compact, Versatile, Integrated Nebulizer-Hydride Generator System for Simultaneous Determination of Volatile Elemental Hydrides and other Elements by ICP-AES
Authors: Fengzhou Qin , Guoying Gu , Chun Xie
Published: July 2005

An integrated nebulizer-hydride generator system has been developed in which an upright spray chamber for pneumatic nebulization is modified for use in hydride generation. The modifications were made to allow the upright spray chamber to function as a phase separator for hydride generation, as well as to permit the nebulized aerosol to pass smaller-diameter droplets. This system allows analyses of both volatile hydrides and conventional pneumatically nebulized solutions to be performed individually or simultaneously without the need to change or disassemble the sample introduction system. The line intensities of As, Sb, Bi, and Hg are essentially not affected by changing the hydride-forming reaction tube length, while decreasing the tube length has the advantage of reducing the interference effect of the transition elements. Detection limits for the elements forming volatile hydrides are improved by one to two orders of magnitude, while the detection limits for other elements remain essentially unchanged or are slightly degraded.
Quantitative Analysis of Additives in Low-Density Polyethylene Using Infrared Spectroscopy and Multivariate Calibration
Authors: Vigerust B. , Kolset K. , Nordenson S. , Henriksen A. , Kleveland K.
Published: July 2005

Multivariate calibration methods have been used to establish a new method for measurements of three selected additives in low-density polyethylene. The determination of the concentration of silica, erucamide, and butylhydroxytoluene (BHT) is based on infrared (IR) spectroscopy and a calibration model. The concentrations are between 20 and 1100 wt/ppm. Compared to traditional chemical analyses, the new method is both time and cost effective and is more precise. The method has potential for quality control of polyethylene.
A Method for the Determination of the Zero-Path-Difference Position in a Fourier Transform Infrared Spectrometer: Application to Magnetic Vibrational Circular Dichroism
Authors: Yoo Ryong K. , Croatto Paul V. , Wang Baoliang , Keiderling Timothy A.
Published: July 2005

Some modern FT-IR spectrometers, without a white light source, use a pre-scan of the signal to determine the zero path difference for purposes of scan initialization. The interferograms in vibrational circular dichroism (VCD) and other low signal-to-noise ratio experiments have little or no centerburst, which can cause problems. This can lead to wasted data collections and to instabilities between successively collected blocks of scans. In this modification, a PbSe detector is used to detect frequencies above 2200 cm−1 extracted from a small fraction of the beam. This near-IR signal is then added to the demodulated differential signal to enable the instrument to initialize scans. Since, in this example, the VCD spectra are typically obtained below 2000 cm−1, there is no spectral interference between the two detector signals. However, use of two signals from different detectors can lead to phase problems, which have been solved with the use of polarization calibration methods. As an example, construction of such a modified spectrometer for magnetic VCD measurement is described in detail. At 0.5 cm−1 resolution, these modulated spectra evidence resolution of the rotational structure in the bands. Such data were unobservable with the unmodified instrument.
Performance of a Laminar Flow Torch/Microwave Plasma Detector for Gas Chromatography
Authors: Jiang M. R. , Fielden P. R. , Snook R. D.
Published: July 2005

The performance of a laminar flow plasma torch as a part of an emission detector for gas chromatography (GC) is evaluated. The effect of plasma gas flow rate on peak height and chromatographic resolution is discussed. Operation stabilities, both short-term and long-term, are presented together with calibration plots for the test elements, carbon and chlorine, as components of separated solvents.
FT-Raman Spectroscopy with Fiber-Optic Probes and a Diode-Bar-Pumped Nd:YAG Laser
Authors: Zimba C. G. , Rabolt J. F.
Published: July 2005

FT-Raman spectroscopy has been demonstrated to be a useful technique for measuring spectra in the absence of interfering fluorescence. Previous measurements have used conventional 90° or 180° sampling geometries, with the use of lenses or mirrors. In this paper, spectra have been measured with the use of a bifurcated fiber-optic bundle, which both delivers the laser excitation to the sample and collects the scattered light, delivering it to the spectrometer. The sampling is easy and routine, requiring almost no sample alignment, and provides a quick and convenient method of remote sampling. Additionally, a prototype diode-bar-pumped Nd: YAG laser was used as the excitation source. This compact laser provides more than adequate power to allow the acquisition of high-quality Raman data. A comparison between this laser and a more conventional flash-lamp-pumped Nd:YAG laser is made.
Infrared Study of Methyl and Ethyl Alkanoates in Carbon Tetrachloride and Chloroform Solutions
Authors: Nyquist Richard A.
Published: July 2005

The reaction field, steric and inductive effects, and intermolecular hydrogen bonding appear to be involved in explaining the frequency behavior of methyl and ethyl alkanoates when in CHCl3 and/or CCl41% solutions.
A New Scattered Circular Polarization Raman Optical Activity Instrument Equipped with a Charge-Coupled-Device Detector
Authors: Hecht Lutz , Che Diping , Nafie Laurence A.
Published: July 2005

A simple and fully computer-controlled scattered circular polarization Raman optical activity (SCP-ROA) instrument is described which consists of a fast single monochromator and a thermoelectrically cooled charge-coupled-device (CCD) detector as the key spectral elements. A conventional circular analyzer, formed by a quartz zero-order quarter-wave plate attached to a motorized 360° rotator and a fixed linear dichroic sheet polarizer, is employed for the modulation between orthogonal circular polarization states in the scattered radiation within a right-angle scattering geometry. Well-resolved depolarized SCP-ROA spectra of (1S)-(–)- α-pinene and (R)-(+)-pulegone are presented within the wave-number region of ∼550 to 1200 cm−1 as typical examples of the excellent performance of this novel multichannel ROA instrument.
On the Effect of Calibration and the Accuracy of NIR Spectroscopy with High Levels of Noise in the Reference Values
Authors: Aastveit Are Halvor , Marum Petter
Published: July 2005

In modern forage breeding the use of near-infrared reflectance spectroscopy is becoming more and more common for estimating quality parameters such as In Vitro Dry Matter Digestibility (IVDMD) and protein. In this paper a systematic study of the method is made and compared with the conventional method described by Tilley and Terry (1963). The results show that there is good agreement between the method based on the NIRS technique and the conventional method. However, compared with the conventional method, the NIRS method gives much more stable and repeatable results (STD = 1.24 for the conventional method, but STD = 0.30 for the NIRS-based method). A new calibration was done after some small modifications on the equipment were carried out. The result of the IVDMD calculated by use of the NIRS method after the new calibration gave some bias and a larger standard deviation (STD = 0.40), as compared to results for the original analysis. The results are, however, still much more stable than those for the conventional method.
Conversion of Methanol to Dimethylether over ZSM-5 by DRIFT Spectroscopy
Authors: Martin K. A. , Zabransky R. F.
Published: July 2005

A diffuse reflectance infrared study of the dehydration of methanol to dimethylether over ZSM-5 catalyst is presented. Between 125° and 200°C, dimethylether is formed and a possible stable intermediate in the nucleophilic attack on surface methoxide groups by methanol is observed on the acid form of the zeolite. This species occupies two OH sites in close proximity. In contrast to the deactivated zeolite, the acid form of ZSM-5 shows an increase in the concentration of terminal silanol groups as the temperature is increased above 100°C and a concurrent increase in reflectivity in the region of the lattice overtone and combination modes.
High-Molecular-Weight Polymer Analysis by Laser Microprobe Fourier Transform Ion Cyclotron Resonance Mass Spectrometry
Authors: Brenna J. T. , Creasy W. R.
Published: July 2005

The frequency-quadrupled output of a Nd:YAG laser (266 nm) is focused to a spot of about 10 micrometers diameter and used to ablate eight industrially important polymers of known composition within a Fourier transform ion cyclotron resonance mass spectrometer (FTICR). The spectra usually show distinct and dramatic differences compared with those obtained with conventional laser microprobes based on a time-of-flight approach. Although rearrangement products are more prevalent than structural ions, the spectra are directly distinguishable by qualitative inspection. Spectra are consistent with two simple mechanisms for formation of rearrangement products: carbon clustering and condensation of stable subunits. High-mass C clusters resembling the “fullerenes,” including a particularly prominent C60 peak, are observed for poly(phenylene sulfide). Other polymers show low- and intermediate-mass C cluster distributions in positive-ion spectra. Odd-mass ion series which are consistent with the formula HA mB n+, where A and B are molecular fragments or atoms, are observed. Negative-ion spectra generally show more structural information than corresponding positive-ion spectra.
A Correction Method for Fluorescence Reduction Using Time-Resolved Fluorometry and Spectrophotometry
Authors: Matsui Tetsuya , Suzuki Kazumichi , Sakagami Masaharu , Kitamori Takehiko
Published: July 2005

A method to correct fluorescence reduction due to foreign materials and temperature using time-resolved fluorometry and spectrophotometry has been developed. The factors taken into consideration were dynamic quenching and inner filter effects on the excitation beam and the fluorescence, and the fluorescence intensity with respect to these factors was theoretically analyzed. A theoretical approach for correcting the fluorescence intensity was obtained, with the use of the fluorescence lifetime, the absorbance at the excitation wavelength, and the absorbance at the fluorescence wavelength. Since these parameters are observable, a novel method can be applied to samples in cases where foreign materials and temperature are unknown. The proposed correction method is also suitable for noncontact and remote measurements. From experiments using a UO22+ ion, the proposed method was verified.
Comparison of Photoacoustic and Diffuse Reflectance Infrared Spectroscopy as Near-Surface Analysis Techniques
Authors: Yang Charles Q.
Published: July 2005

Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) has been applied as a near-surface analysis technique for various types of samples. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) also was reported for characterizing surface species of fibrous materials. In this research, chemically modified textile fabrics, fibers, and films were studied by both FT-IR/PAS and DRIFT. The capability of near-surface analysis for both techniques was evaluated and compared. Even though diffuse reflectance infrared spectra show an enhancement in the band intensity of near-surface species, FT-IR/PAS appears to have a much smaller sampling depth than DRIFTS. All the data demonstrate that FT-IR/PAS is a useful near-surface analysis technique for polymeric fibers and films.
Hadamard Multiplex Multichannel Spectroscopy to Achieve a Spectroscopic Power Distribution Advantage
Authors: Vickers Thomas J. , Mann Charles K. , Zhu Jianxiong
Published: July 2005

A Hadamard approach employing an encoding mask at the entrance to a spectrograph and a multichannel detector is described. This approach provides an energy throughput advantage which should prove important for a variety of emission-mode measurements requiring collection of radiation from an extended source. The performance of the system is demonstrated for mercury lamp atomic emission and rhodamine B fluorescence measurements. Simulations are used to investigate mechanical requirements in the construction of the system.
Phase-Resolved Fluorescence Spectral Fingerprinting of Petrolatums
Authors: Hertz Patricia M. Ritenour , McGown Linda B.
Published: July 2005

The first application of multifrequency phase-resolved fluorescence spectroscopy (PRFS) to the characterization of a complex, multicomponent system is described. The incorporation of lifetime selectivity significantly enhances the ability to discriminate between different petrolatum samples, relative to conventional, steady-state fluorescence techniques. Chemometric data analysis strategies are used to reduce noise contributions and to compare the dynamic spectral features of the petrolatums.
The Effect of Pyrolysis and Instrument Parameters on the Results of Various Supervised Learning Techniques
Authors: Voorhees Kent J. , Sarver Emory W. , Harrington Peter B. , Deluca Stephan J.
Published: July 2005

Four supervised pattern-recognition procedures—linear discriminant analysis, soft-independent models of class analogy, a univariate expert system, and a multivariate expert system—were applied to pyrolysis-mass spectrometry data from five bacterial species. A test set was generated by individually modifying the tuning parameters of the mass spectrometer followed by collection of one spectrum for each bacteria. Five replicate pyrolysis-mass spectra of each bacteria were used as a training set for the classification of the test set. The multivariate expert system consistently scored over 92% correctly identified, while the other procedures resulted in less than 80% correctly identified. Under these harsh conditions, the multivariate expert system was not affected seriously by the mass spectrometer tuning changes.
JCAMP-CS: A Standard Exchange Format for Chemical Structure Information in Computer-Readable Form
Authors: Gasteiger J. , Hendriks B. M. P. , Hoever P. , Jochum C. , Somberg H.
Published: July 2005

The JCAMP-DX format provides a Standard for the exchange of data on IR spectra. Extensions of this format to other spectral data are being developed. Spectral data should always be accompanied by information on the chemical structure of the investigated compounds. The JCAMP-CS format provides definitions for exchanging information on the composition and the stereochemistry, as well as on the 2D and 3D atomic coordinates, of chemical structures. Where possible, the standard was designed to adhere to the conventions of JCAMP-DX. In addition, care was taken to make as simple as possible the conversion to other formats in use for representing chemical structures.
Polycyclic Aromatic Nitrogen Heterocycles. Part II: Effect of Solvent Polarity on the Fluorescence Emission Fine Structure of Three Azapyrene Compounds
Authors: Tucker Sheryl A. , Acree William E. , Tanga Mary J.
Published: July 2005

Fluorescence emission spectra are reported for 1-azapyrene, 2-azapyrene, and 4-azapyrene dissolved in several nonelectrolyte solvents of varying polarity. Results of these measurements show that all three solutes are unsuitable for solvent polarity probes, as the calculated emission intensity ratios remain nearly constant, irrespective of solvent polarity. Abnormal fluorescence behavior was also noted for 1-azapyrene and 2-azapyrene dissolved in several chlorinated solvents. Time-dependent fluorescence spectra for 1-azapyrene in dichloromethane suggest a possible photochemical reaction between the PANH solute and chlorinated solvent molecule.
Collinear Photothermal Deflection Spectroscopy of Liquid Samples at Varying Temperature
Authors: Spear Jonathan D. , Silva Robert J. , Klunder Gregory L. , Russo Richard E.
Published: July 2005

The method of photothermal beam deflection was demonstrated for measuring the absorption spectrum of an aqueous Nd3+ solution at temperatures between 25°C and 90°C. Changes in the magnitude of the observed deflection can be correlated with the temperature dependence of both the absorptivity of the Nd3+ ions and the physical properties of the solvent, most notably the thermo-optic coefficient d n/d T.
Universal Approach for Determination of Physical and Chemical Properties of Water by Near-IR Spectroscopy
Authors: Lin Jie , Brown Chris W.
Published: July 2005

Near-IR spectroscopy has been investigated as a universal approach for determination of physical and chemical properties of water and their functions of temperature. Principal component regression and multilinear regression models were used to correlate the spectra with the properties of water at temperatures between 5 and 65°C. Fifteen properties of water were investigated including density, refractive index, dielectric constant, relative viscosity, surface tension, vapor pressure, sound velocity, isothermal compressibility, thermal expansivity, thermal capacity, thermal conductivity, enthalpy, free energy, entropy, and ionization constant. Very good correlations were found between the near-IR predicted values of all the properties and those obtained by the traditional methods. This investigation demonstrates that these fifteen properties of water can be simultaneously determined simply by measuring a set of near-IR spectra of water, and, thus, near-IR spectroscopy can be used as a universal method for the determinations of physical and chemical properties of water. Remote sensing of the properties can be performed with the use of a fiber-optic sensor.
Ice/Solid Adhesion Analysis Using Low-Temperature Raman Microprobe Shear Apparatus
Authors: Sonwalkar Nishikant , Sunder S. Shyam , Sharma S. K.
Published: July 2005

In order to understand the molecular mechanics involved in the adhesion of a bimaterial interface bond, a Raman microprobe shear apparatus has been designed and fabricated. The apparatus is fabricated to perform a pure shear experiment on a bimaterial interface produced by the vapor deposition of a thin film of ice on a cold metallic substrate under a controlled temperature, humidity, and vapor-flow rate environment. The textures of four metal surfaces (titanium, copper, aluminum, stainless steel) and one polymer surface have been investigated with the use of the scanning electron micrograph. The shear experiment is optically coupled to a Raman microprobe at the 180° and 135° scattering geometry. The Raman spectra provide in situ information regarding the molecular structure and vibrational modes at the bimaterial interface before and after the shearing event. The results indicate that the adhesive bonds are formed primarily by the interaction of oxygen atoms in the ice lattice with the atoms of the solid surface. A solid, which displays good lattice matching with ice, shows good adhesive strength. The adhesive strength is found to be proportional to the extent of mechanical interlocking and inversely proportional to the contact angle of the water droplet. An activation energy analysis of the adhesive strength shows that the failure of the ice/metal bond is rate sensitive while the ice/polymer bond is relatively insensitive to the strain rate. The failure of the ice/metal bond is cohesive while the failure of the ice/polymer bond is interfacial. The structure of the ice layers on metals is polycrystalline, which is marginally influenced by the crystalline structure of the substrate and shows increased ordering in vibrational modes. The sheared ice has a larger number of defects as reflected by the increase in the half-power bandwidth of the Raman peaks.
Vibrational Spectra of Cyclic Polysilanes: Dodecamethylcyclohexasilane, All-trans-Hexabenzylcyclohexasilane, All-trans-Hexaphenylcyclohexasilane, and Dodecaphenylcyclohexasilane
Authors: Li Hongqi , Butler Ian S. , Harrod John F.
Published: July 2005

Infrared and Raman spectra have been recorded at room temperature for the following four cyclohexasilanes: dodecamethylcyclohexasilane, (SiMe2)6 (I); all- trans-hexabenzylcyclohexasilane, [Si(H)CH2Ph]6 (II); all- trans-hexaphenylcyclohexasilane, [Si(H)Ph]6(III); and dodecaphenylcyclohexasilane, (SiPh2)6 (IV). Vibrational assignments have been proposed on the basis of the local symmetries of the silicon ring skeletons ( D3 d) and the substituent groups (Me, C3 v; Ph and CH2Ph, C2 v). The four polysilane oligomers can be readily distinguished from one another by their vibrational spectra. For example, characteristic νSiH and δSiH Raman bands of II and III were observed in the 2150–2075 and 790–600 cm−1 regions, respectively, where the vibrations of III were higher in energy than were those of II. All four oligomers exhibited distinct differences in the νSiC, νSiS, and δSiC regions located below 800 cm−1. Finally, from the observed vibrational band shifts, it appears that the σ-φ hyperconjugation between the Ph groups and Si atoms in the > SiR1R2 fragments decreases in the order: IV (R1 = R2 = Ph) > III (R1 = H, R2 = Ph) > II (R1 = H, R2 = CH2Ph).
Background-Free Species Detection in Sooty Flames Using Degenerate Four-Wave Mixing
Authors: Kröll S. , Löfström C. , Aldén M.
Published: July 2005

The background radiation disturbance in luminous environments has been compared for degenerate four-wave mixing (DFWM) and laser-induced fluorescence (LIF) for OH radical detection in a sooty propane/oxygen flame. The LIF signal generally was considerably stronger than the DFWM signal, but in strongly sooty environments the LIF signal was accompanied by a significant background signal, while the DFWM signal was background-free under all soot loads tested.
Gas-Sampling Glow Discharge for Optical Emission Spectrometry. Part I: Design and Operating Characteristics
Authors: Starn Timothy K. , Pereiro Rosario , Hieftje Gary M.
Published: July 2005

A spectrochemical source for optical emission spectrometry, based on an atmospheric-sampling glow discharge, is described. Operating parameters that affect the performance of the glow discharge are investigated; the most important is the source pressure. Helium and argon are studied as plasma support gases. Simple to build and operate, the glow discharge is fairly robust to introduced organic vapors and produces equivalent signals from carbon-containing species regardless of the original molecular form of the carbon.
Formation and Detection of Fullerene Metal Complexes Using Time-Of-Flight Secondary Ion Mass Spectrometry
Authors: Zimmerman Paul A. , Hercules David M.
Published: July 2005

We have found that metal/fullerene adduct ions of the C60 and C70 fullerenes can be formed with silver, gold, rhodium, and palladium by argon-ion bombardment of fullerenes deposited on a metal substrate, with the use of a Time-of-Flight Secondary Ion Mass Spectrometer (TOF-SIMS). The bis and tris metal/fullerene adducts formed include: Ag(C60)2+, AgC60C70+, Ag(C70)2+, Ag(C60)3+, Ag(C60)2C70+, AgC60(C70)2+, and Rh(C60)2+. In addition, the monomeric adducts AgC60+, AgC70+, AuC60+, AuC70+, RhC60+, RhC70+, and PdC60+ also have been detected. Samples prepared with a raw soot extract gave higher yields of metal/fullerene adducts in TOF-SIMS than those prepared with purified fullerenes. This result may indicate the presence of a matrix component in the raw soot which enhances the formation of fullerene metal adducts. Spectra obtained from the raw soot show peaks at every 24 daltons corresponding to even-numbered carbon clusters. These peaks occur as low as 600 daltons (C50) and as high as 3000 (C250).
Surface-Enhanced Raman Vapor Dosimeter
Authors: Vo-Dinh T. , Stokes D. L.
Published: July 2005

This paper describes a new direct-reading personal dosimeter designed to detect vapors of organic chemicals. The device employs the surface-enhanced Raman scattering (SERS) technique for direct measurement of the amount of analyte collected on the dosimeter, requiring no sample desorption or wet-chemical extraction procedure. The time-weighted average exposure to the chemical vapors can be determined on the dosimeter substrate. The results with benzoic acid used as the model compound illustrate the usefulness of this SERS-based dosimeter.
Rapid Assay for Polystyrene Surface Oxidation
Authors: Bryhan M. , Onyiriuka E. C. , Hersh L. S. , Hertl W.
Published: July 2005

Polystyrene surfaces are often corona-discharge or plasma treated to oxidize the surface, which enhances the wettability. X-ray photoelectron spectroscopy (XPS), which requires time and an ultra-high vacuum, is generally used to measure this surface oxidation. A rapid, simple method for measuring polystyrene surface oxidation is described. The surface is soaked in a solution of Azure A dye, which adsorbs only to oxidized sites on the polystyrene. The excess dye is flushed away and the bound dye is desorbed with a detergent; an absorbance measurement at 635 nm is used to determine the quantity of desorbed dye. This value correlates with the polystyrene surface oxygen concentration and gives r2 = 0.93.
Infrared Study of n-Alkanes in CCl4, CDCl3/CCl4, and CDCl3 0.5% Solutions
Authors: Nyquist R. A. , Fiedler S. L.
Published: July 2005

Three factors appear to affect n-alkane molecular vibrations in CHCl3/CCl4 solutions. These are: (1) Physical restriction of the vCH3 and vCH2 vibrations by solvent molecules. (2) Inter molecular hydrogen bonding between n-alkane protons and the free pair of electrons on Cl atoms of either CCl4 or CDCl3. The positively charged alkane protons arise during the dipole moment changes, δP/δQ, occurring during a full cycle of the vCH3 and vCH2 modes. (3) The physical restriction of solvent molecules, which is greater in the case of CDCl3 than in the case of CCl4 due to a high degree of CDCl3 orientation about n-alkane molecules due to repulsion of the C-D of CDCl3 by the n-alkane vCH3 and vCH2 protons, which allows stronger C-D:Cl bonds to be formed between solute and solvent.
Raman and Near-Infrared Studies of an Epoxy Resin
Authors: Chike K. E. , Myrick M. L. , Lyon R. E. , Angel S. M.
Published: July 2005

A quantitative comparison of Raman and Fourier transform near-infrared (FT-NIR) spectroscopic techniques for the analysis of epoxy curing is performed. It is shown that the Raman technique yields a linear calibration curve much like FT-NIR. Band assignments in the Raman spectrum of diglycidyl ether of bisphenol-A (DGEBA) were performed by studying Raman spectra of smaller model compounds.