bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical Measurement of Toxic Gases Produced during Firefighting Using Halons
Authors: McNesby Kevin L. , Daniel Robert G. , Miziolek Andrzej W. , Modiano Steven H.
Published: October 2003

Several optical techniques (FT-IR emission and absorption spectroscopy, mid- and near-infrared tunable diode laser absorption spectroscopy) have been used to measure toxic gases produced during inhibition of flames by halogenated hydrocarbons (Halons). Fire types studied include low-pressure premixed flames, counterflow diffusion atmospheric-pressure flames, open-air JP-8 (turbine fuel) fires, and confined JP-8 fires. Spectra are presented and analyzed for these fires inhibited by CF3Br (Halon 1301) and C3F7H (FM-200). For low-pressure premixed flames, spectra are presented which show production of the CF3 radical in methane/oxygen/Ar flames inhibited by CF3Br. For large-scale fire testing, it is shown that the type and amount of toxic gases produced during fire inhibition are highly dependent on fire conditions and temperatures and that some species not considered important (CF2O) are often produced in significant amounts. Finally, it is shown that HF production, during inhibition of vehicle fires using FM-200, is highly dependent on time to suppression.
Principal Component Analysis of Near-Infrared Spectra of Alteration Products in Calcareous Samples
Authors: Bacci M. , Porcinai S. , Radicati B.
Published: October 2003

Principal component analysis (PCA) of diffuse reflectance near-infrared (NIR) spectra has been used as a suitable methodology for discriminating areas involved in the sulfation process of calcareous stones. NIR spectra of standard mixtures containing CaSO4 · 2H2O, CaSO3 · 1/2H2O, and CaCO3 were recorded. For all data sets submitted to PCA, a good discrimination between the two reaction products, i.e., CaSO3 · 1/2H2O and CaSO4 · 2H2O, in the alteration process was obtained. The actual availability of fiber-optic spectrum analyzers working in the NIR region suggests that the proposed procedure can be used as a safe and nondestructive method for monitoring alteration processes in calcareous works of art.
Analysis of the Antisapstain Chemical Didecyldimethylammonium Chloride (DDAC) on Wood Surfaces by Diffuse Reflectance Fourier Transform Infrared Spectroscopy
Authors: Manville J. F. , Nault J. R.
Published: October 2003

Reflectance FT-IR has been shown to be a promising technique for rapid (≤2 seconds) quantitative determinations of the antisapstain chemical didecyldimethylammonium chloride (DDAC) on wood surfaces treated at 0 to 88 μg/cm2. Partial least-squares analysis allowed selection of a region of the infrared spectra which could be used for quantitative analyses of DDAC on the wood. The results obtained through this method were comparable to results obtained on the same samples by HPLC and pyrolysis–gas chromatography/mass spectroscopy. This outcome demonstrates the opportunity for applying this FT-IR technique in an industrial setting.
Investigation of the Analytical Performance of an MDMI-ICP-AES System
Authors: Lazar Alexandru C. , Farnsworth Paul B.
Published: October 2003

A 40-MHz ICP was equipped with a novel sample introduction system capable of introducing monodisperse droplets into the plasma with 100% efficiency. The analytical performance of the system was investigated by using two different synchronous detection techniques. The detection limits determined for Ba with ensemble averaging and with boxcar averaging were 0.048 ng/mL and 0.063 ng/mL, respectively. Signal stability in time, effect of the matrix on barium ionic emission intensity, vertical emission profiles from a multicomponent solution, and washout time of the system were also studied.
Near-IR versus Mid-IR: Separability of Three Classes of Organic Compounds
Authors: Stallard Brian R.
Published: October 2003

Recently there has been a surge of interest in spectroscopic sensors operating in the near-IR, although it is recognized that the mid-IR contains more spectral information. The general question addressed in this paper is, How much specificity is lost in choosing the near-IR over the mid-IR for sensor applications? The example considered is the separability among three classes of organic compounds: alkanes, alcohols, and ketones/aldehydes. We use spectra from two sources: the Hummel polymer library (mid-IR) and the library of Buback and Vögele (near-IR). This is the first paper on class separability to make use of this new near-IR library, available in digital form only since July 1995. Five spectral regions are considered: region 5, 10,500 to 6300 cm−1; region 4, 7200 to 5200 cm−1; region 3, 5500 to 3800 cm−1; region 2, 3900 to 2500 cm−1; and region 1, 2500 to 500 cm−1. Class separability is explored both qualitatively and quantitatively with the use of principal component scatter plots, linear discriminant analysis, Bhattacharyya distances, and other methods. We find that the separability is greatest in region 1 and least in region 2, with the three near-IR regions being intermediate. Furthermore, we find that, in the near-IR, there is sufficient class separability to ensure that organic compounds of one class can be determined in the midst of interference from the other classes.
Chemical Bonding of Tetraethylenepentamine to Nitric Acid-Oxidized Carbon Fibers: An XPS/ISS Investigation
Authors: Gardner Steven D. , Singamsetty Chakravarthy S. K. , He Guoren , Pittman Charles U.
Published: October 2003

The surface reaction of tetraethylenepentamine (TEPA) with nitric acid-oxidized type II PAN-based carbon fibers has been investigated by using X-ray photoelectron spectroscopy (XPS), ion scattering spectroscopy (ISS), and acid/base surface titrations. Initially, nitric acid treatments of varying intensity impart different quantities of oxygenated functional groups onto the fibers, and surface roughening due to formation of pits and crevasses occurs. Subsequent treatment with TEPA at 190 °C introduces significant amounts of surface-bound TEPA via reaction with carboxyl groups on the oxidized carbon fiber surfaces. Angle-resolved XPS (ARXPS) spectra are consistent with a TEPA surface concentration that varies as a function of depth (into crevasses and pits) and remains greatest primarily within the outermost 15 Å. The extent of the TEPA surface reaction is proportional (but not linearly) to the fibers' initial oxygen content. Nonlinearity may be due to several factors including (1) decomposition of a portion of the carbon fibers' carboxyl groups under the TEPA reaction conditions and (2) a nonuniform reaction with the commercial TEPA mixture, which contains several different pentamine molecular structures together with small amounts of tetra- and hexamine impurities. An accurate determination of the TEPA bonding configuration is difficult to achieve; however, the data suggest that at least 70% of the TEPA molecules form two (or more) bonds to the carbon fiber surfaces.
Compression of Infrared Spectral Data Using the Fast Wavelet Transform Method
Authors: Chau F. T. , Gao J. B. , Shih T. M. , Wang J.
Published: October 2003

The wavelet transform method was used to compress experimental infrared spectra. The methodology utilized was based upon the fast wavelet transform method coupled with the multiresolution signal decomposition, as well as the optimal bit allocation quantization and Huffman coding techniques. The proposed algorithm was applied to reduce the storage space of infrared spectra of several chemicals. The results obtained were compared with those from the fast Fourier transform and the wavelet-based thresholding methods. It was found that the proposed method outperforms the other two.
Generation of 1.30- to 1.55-μm Tunable Radiation from First Stokes Raman Shifting in Hydrogen
Authors: Aniolek Kenneth W. , Miller David L. , Cernansky Nicholas P. , Owens Kevin G.
Published: October 2003

Raman shifting to the near-infrared, when possible, provides a simple and economical alternative to the optical parametric oscillator (OPO) or difference frequency mixing approach. We report the production of 1.30- to 1.55-μm radiation from first Stokes Raman shifting in a single-pass, open (no capillary waveguide), hydrogen-filled Raman cell (constructed in-house) pumped with a Nd:YAG/dye laser combination operating near 900 nm. A maximum of 10 mJ (19% efficiency) of first Stokes energy was measured for the highest cell pressure (490 psia) and input pulse energy (53 mJ). The quality of the first Stokes output is similar to the dye laser output as indicated by polarization, shot-to-shot energy fluctuation, beam diameter, and linewidth. A characterization of the Stokes and anti-Stokes output was also conducted including one-dimensional spatial intensity profiles and output line dependence on input pulse energy and cell pressure. A large first Stokes conversion efficiency has been attributed to little production of higher-order Stokes and anti-Stokes lines.
Infrared Reflection Absorption Spectroscopy of Naturally Grown Oxide Films on Chrome and the Dependence of the Berreman Effect on Film Thickness
Authors: Scherübl Th. , Thomas L. K.
Published: October 2003

The thickness dependence of the Berreman effect for naturally grown oxide films on chrome is analyzed theoretically and experimentally. The shift of the spectral position of the Berreman minimum can be described by the Fuchs–Kliewer theory of virtual modes. Both the absorption and the shift of the position can be used for thickness determination. The experimental results compared with calculated values based on different optical constants for Cr2O3 indicate their influence on the position and the absorption of the Berreeman minimum.
Research Strategy for the HPLC/FT-IR Analysis of Drug Metabolites
Authors: Pivonka D. E. , Kirkland K. M.
Published: October 2003

A strategy for the infrared spectroscopic analysis of drug metabolites in high-pressure liquid chromatography (HPLC) effluent is presented with a primary focus on delivery of metabolite structure as opposed to development of dedicated or automated instrumentation. This paper stresses the complementary nature of on-line (solution phase) and off-line (condensed phase) HPLC Fourier transform infrared (FT-IR) implementations for structural elucidation of drug metabolites.
Electron Paramagnetic Resonance and Mass Spectroscopy Study of Spin-Trapped Radicals: Styrene—Amine Photoreactions
Authors: Lin Chiou-Rong , Pan Kai , Ho Tong-Ing
Published: October 2003

The free radical intermediates from the photolysis of eleven substituted styrenes (1–11) with both tertiary and secondary amines were studied by spin trapping and the high-pressure liquid chromatography electron paramagnetic resonance (HPLC-EPR) technique. Eleven α-methylbenzyl radicals were trapped by 2-methyl-2-nitro-sopropane (MNP) and separated by HPLC. Resolution enhancement was applied to obtain long-range hyperfine splitting constants (hfsc). The nitrogen hfsc are linearly correlated with the Hammett substituent constants. The major mass spectral fragments for the trapped aminoxyl radicals (12–22) include [M+1]+, [M–1]+, [M– tBu]+, [M– tBuOH]+, [M– tBuNO]+, and [(CH3)3C]+. The structures of 12–22 were also confirmed by chemical synthesis by adding Grignard reagent to α-phenyl- N- tert-butylnitrone (PBN) and its derivatives.
Rayleigh Scattering of Excimer Laser Light from Some Simple Molecules at 193 nm and 248 nm: The Effect of Polarization upon Imaging Diagnostics
Authors: Reckers Wolfgang , Gu Yongwei , Rothe Erhard W. , Voges Heinrich
Published: October 2003

Tunable excimer laser beams are increasingly used for imaging of combustion and/or flow systems. We (1) describe the need to use known polarization phenomena in interpreting diagnostics based on Rayleigh scattering (RS); (2) present relative RS cross sections for some important species at the most relevant wavelengths, 193 and 248 nm; and (3) measure the degree of linear polarization and the locking efficiency of the excimer beam, which are important diagnostic parameters that are otherwise difficult to obtain. Laser sheets, whose direction of linear polarization are adjustable, pass through gases. The Rayleigh light goes into intensified charge-coupled dervice (CCD) cameras. We report RS cross sections, normalized to those for N2, at 193 nm for H2, O2, H2O, CO2, and CH4, and at 248 nm for Ar, H2, O2, H2O, CO2, and CH4. Even when these normalized RS cross sections are used, the diagnostics can be very sensitive to the laser beam's polarization state. For example, for CO2, the normalized cross section changes by a factor of 4 with polarization. This usually unwanted sensitivity is greatest when an unmodified tunable excimer laser is used. The degree of polarization of the lasers, as well as their locking efficiency, is derived via RS from the spherical molecules Ar and CH4.
Sampling Strategy and Direct Solid Sampling Electrothermal Atomization Atomic Absorption Spectrometric Analysis of Trace Elements in Animal Tissue
Authors: Lücker Ernst
Published: October 2003

The influence of analyte distribution on analytical results of direct solid sampling and electrothermal atomization atomic absorption spectrometry with direct Zeeman-effect background correction (SS-ZAAS) was studied with the use of nonhomogenized livers of mallards and fallow deer and hierarchic sampling schemes. Significant differences were observed by means of the analysis of variance in lead content of left and right lobes as well as of randomly distributed sampling sites of a deer liver. For the first time SS-ZAAS distribution analysis gave variances dominated by analyte distribution. The distribution analyses of mercury in livers of mallards gave significant effects of sampling sites in 6 out of 10 livers; however, in all cases variance as caused by analyte distribution was observed to be lower than residual variance. Allowing for heterogeneity, the minimal total variance is reached for a given number of replicates when each test sample is taken from a different site of the organ. Despite increased imprecision, the uncertainty of direct solid sampling is thus minimized effectively.
Determination of Zr and Ti in 3-μm-Thick ZrTiN Ceramic Coating Using Laser Ablation Inductively Coupled Plasma Atomic Emission Spectrometry
Authors: Kanicky Viktor , Musil Jan , Mermet Jean-Michel
Published: October 2003

Analysis of 3-μm-thick ZrN, TiN, and ZrTiN ceramic coatings on a high-speed steel substrate by laser ablation inductively coupled plasma atomic emission spectrometry (LA-ICP-AES) is described. A Nd:YAG laser was used in the Q-switched mode and operated at 355 nm and 5 mJ. Ablation patterns were obtained on the target surface by moving the ablation chamber with respect to the laser beam by means of an X-Y translator. Control of the depth of penetration was obtained by successively performing a limited number of cycles. Transient signals were obtained and their peak areas were used for the construction of calibration graphs based on the concentrations determined by energy-dispersive X-ray (EDX) analysis. An erosion rate of 0.1 μm per cycle was observed. Crater shape and depth, temporal behavior, and reproducibility of the signals are described.
Influence of Sample Surface Condition on Chemical Analysis Using Laser Ablation Inductively Coupled Plasma Atomic Emission Spectroscopy
Authors: Mao Xianglei , Chan Wing-Tat , Russo Richard E.
Published: October 2003

The influence of sample surface condition on chemical analysis was investigated when using laser ablation sampling with inductively coupled plasma atomic emission spectroscopy (ICP-AES). The ablated mass quantity and composition were found to be significantly different from original vs. pre-ablated surfaces. The ablated mass quantity from original surfaces was much greater than that from pre-ablated surfaces, and the ablation rate (mass per unit area and time) was constant or independent of power density below 0.3 GW/cm2. For pre-ablated surfaces, the mass ablation rate follows exponential behavior in the same power density region. The measured composition of the ablated mass was found to be dependent on the surface condition and laser power density, for both original and pre-ablated surfaces. Understanding the influence of laser energy and surface conditions on mass ablation is essential for accurate and precise chemical analysis.
Determination of Cobalt in Soil, Steel, and Graphite Using Excited-State Laser Fluorescence Induced in a Laser Spark
Authors: Gornushkin I. B. , Kim J. E. , Smith B. W. , Baker S. A. , Winefordner J. D.
Published: October 2003

An LIBS/LEAFS (laser-induced breakdown spectroscopy/laser-excited atomic Fluorescence spectrometry) combination with the use of simple open-air ultraviolet (UV) ablation has been investigated in terms of its analytical possibilities for the determination of cobalt in three solid sample matrices: graphite, soil, and steel. The fluorescence of cobalt was excited from a level which was already populated in the ablation plasma and was monitored at the Stokes-shifted wavelength. The optimal time delay between the ablating and exciting pulses was 16 μs. Detection limits in the ppb to ppm range and linearity over about four orders of magnitude were obtained. Excellent correlation of the LIBS/LEAFS with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and the certified value for Co in an SRM soil standard showed that both the precision and the accuracy of the LIBS/LEAFS method were satisfactory.
Direct Analysis of Silicon Carbide Powder by Total Reflection X-Ray Fluorescence Spectrometry
Authors: Csató I. , Záray GY. , Gál-Solymos K. , Hassler J.
Published: October 2003

Three silicon carbide powders having different grain size distributions were analyzed by total reflection X-ray fluorescence (TXRF) spectrometry with the application of slurry sampling. For the elements investigated (Fe, Ti, V, Cu, Ni, and Ca) the line-to-background ratios show a maximum value at a surface concentration of 12.5 μg/mm2. For the realization of this surface concentration, a 25-μL aqueous slurry with a concentration of 1% (m/V) and pH of 10 was dropped onto the hydrophobic quartz carrier plate. For quantification of the intensity data, gallium was added as an internal standard to the slurries. Under these experimental conditions, the analytical data of the fine-grained powders (80–90% of the powder particles were less than 1.5 μm) are in good agreement with concentrations determined in various laboratories by inductively coupled plasma atomic emission spectrometry (ICP-AES), ICPmass spectroscopy (MS), electrothermal vaporization- (ETV)-ICP-AES, slurry sampling graphite furnace atomic absorption spectroscopy (GF-AAS), and neutron activation methods. Powders with a mean grain size greater than 1.5 μm deviate much more from the reference data. Calculated limits of detection (LODs) range from 2 to 25 μg/g. The precision expressed as relative standard deviation (RSD) varies between 4 and 14% for Fe, Ti, and V, whose concentrations in the fine-grained silicon carbide samples exceed by a minimum of tenfold their limits of detection; however the precision is very poor for Cu (66.6%) and Ni (62.3%), which have concentrations near the limits of the detection.
Automated Image Background Removal in Line-Imaging Raman Spectroscopy
Authors: Haight Scott M. , Schwartz Daniel T.
Published: October 2003

Several automated image background removal schemes for use with line-imaging Raman spectroscopy are compared. An image of electrodeposited β-CuSCN produced by line-imaging Raman spectroscopy (one spectral dimension, one spatial dimension) is background-corrected by the adapted Pearson's method (APM), a Fourier filtering method, and the mathematical morphology method of the rolling cylinder. APM is shown to perform best overall, but is the most computationally taxing because of the iterative nature of the algorithm. The effects of the APM parameters are discussed.
New Device for Raman Difference Spectroscopy with Multichannel and Scanning Multichannel Detection
Authors: Deckert V. , Liebler W. , Eck R. , Kiefer W.
Published: October 2003

We report on a specially designed setup which combines the advantages of Raman difference spectroscopy with the multiplex advantages of multichannel detection. The new device and the principle of operation are described in detail. Several examples of Raman difference spectra are shown to demonstrate the performance of the setup. Static as well as scanning multichannel techniques were applied to test the distinct capabilities of the system. Both methods are discussed with special emphasis on the reliability and accuracy of the results obtained.
Theoretical Foundations for a New Family of Infrared Four-Wave Mixing Spectroscopies
Authors: Wright John C. , Chen Peter C. , Hamilton James P. , Zilian Arne , Labuda Mitchell J.
Published: October 2003

A new family of selective four-wave mixing methods, based on the establishment of vibrational nonlinear polarizations with multiple resonances, is proposed. This family includes double-infrared resonances, vibrationally enhanced Raman resonance, and vibrationally enhanced two-photon resonance. These methods are related to traditional Raman and infrared spectroscopy, but the methods are shown to have the capabilities for component and conformer selectivity, line-narrowing of inhomogeneously broadened vibrational transitions, and mode selection. The theoretical foundations for the methods are developed and directed to possible applications.
Spectrochemical Analysis of Liquids Using Laser-Induced Plasma Emissions: Effects of Laser Wavelength on Plasma Properties
Authors: Ng C. W. , Ho W. F. , Cheung N. H.
Published: October 2003

We spectroscopically determined the temperature and electron density of the plasma plumes produced by pulsed-laser ablation of aqueous solutions containing sodium, lithium, and rubidium. With the use of a Nd:YAG laser at 532 nm and fluence of 3 J/cm2, the plasma produced was hot (low eV range) and extensively ionized, with electron density in the 1018 cm−3 range. Analyte line signals were initially masked by intense plasma continuum emissions and would only emerge briefly above the background when the plume temperature dropped below 1 eV during the course of its very rapid cooling. Since ionization was thermally induced, the intense plasma flash was inevitable. In contrast, 193-nm laser ablation at similar fluence generated plasmas of much lower (<1 eV) temperature but comparable electron density. Plasma continuum emissions were relatively weak, and the signal-to-background ratio was a thousand times better. Consequently, this “cold” plasma was ideal for sampling biologically important elements such as sodium, potassium, and calcium.
Instrumental Resolution Considerations for Fourier Transform Infrared Gas-Phase Spectroscopy
Authors: Jaakkola P. , Tate J. D. , Paakkunainen M. , Kauppinen J. , Saarinen P.
Published: October 2003

Instrumental resolution has a significant effect on the performance of Fourier transform infrared (FT-IR) spectrometers used for gasphase analysis. Low-resolution FT-IR spectroscopy offers some valuable advantages compared with the traditional high-resolution FT-IR gas-phase spectroscopy, especially in nonlaboratory environments. First, high signal-to-noise ratio (SNR) spectra can be acquired in field conditions without the use of traditional liquid nitrogen-cooled detectors. Second, the dynamic range for quantitative analysis is larger for low-resolution spectroscopy than for high-resolution due to the lower absorbance values and lower noise levels. Third, spectral analysis speed is increased and data storage requirements are substantially reduced. The purpose of this study was to investigate the effect of instrumental resolution on FT-IR gas-phase analysis. The effects of spectral resolution on sensitivity, selectivity, accuracy, precision, spectral overlap, dynamic range, and nonlinearity are separately discussed.
Study of Surface-Enhanced IR Absorption Spectroscopy over Evaporated Au Films in an Ultrahigh Vacuum System
Authors: Sato Shinri , Suzuki Toshihiro
Published: October 2003

IR transmission spectra were measured in an ultrahigh vacuum system for Fe(CO)5, n-decane, and NH3 adsorbed at <150 K on transparent Au films evaporated on a sapphire plate. The spectra of Fe(CO)5 show ∼10-fold enhancement as compared to those observed on an SiO2 lm coated on a sapphire plate, which has been reported as surface-enhanced IR-absorption (SEIRA). The enhancement is reduced when the coverage of adsorbate exceeds a mono-layer or other molecules present on the surface prior to adsorption, indicating that SEIRA is effective only in the close vicinity of the surface. The SEIRA effect is also reduced when film is heated in a vacuum, probably because of sintering of the Au particles forming the film. In addition, the heat treatment of the film results in blue shifts of bands, accompanied by some band distortion. With the use of SEIRAS, the surface photochemistry of Fe(CO)5 has been investigated.
Quantitation of Poly(Ethylene Glycol) Concentration Using Raman Spectroscopy
Authors: Meléndez Yanira , Schrum Kimberley F. , Ben-Amotz Dor
Published: October 2003

This study uses Raman spectroscopy to quantitate the amount of polymer in solution, in particular poly(ethylene glycol) dissolved in chloroform. For various chain lengths and polymer weight fraction ranges, it is shown that the ratios of peak intensities in the C–H stretching region may be used to quantitate polymer weight fraction with about 1% uncertainty. For low polymer weight fraction ranges (0–10%), the relationship between Raman intensity and polymer weight fraction is essentially linear, while at higher ranges (0–50%) the intensity follows a nonlinear function derived from basic concentration relationships and indicates a universal scaling with polymer chain length.
Interpolation of Spectral Data Using the Shift Theorem of the Discrete Fourier Transform
Authors: Eskola Sisko Maria , Stenman Folke
Published: October 2003

We present a method for interpolating discrete spectral data using the shift theorem of the discrete Fourier transform. The advantages of the method as compared to ordinary curve fitting and similar direct interpolation methods are that, being based on the discrete Fourier transform, our method is also very fast for large sample volumes if used with the fast Fourier transform (FFT) algorithm. In contrast to direct interpolation methods in spectral space, our method does not modify the modulus of the inverse Fourier transform of the shifted profile, so that the spectral content of the signal is preserved. The basis of the method also makes it suitable for analyzing hot-band structures in vibrational spectra. The method is illustrated with two examples.
Elemental Fractionation of Glass Using Laser Ablation Inductively Coupled Plasma Mass Spectrometry
Authors: Figg Deborah , Kahr Michael S.
Published: October 2003

Three laser wavelengths (1064, 532, and 266 nm) were employed for laser ablation at varied laser pulse energies to study the effect of irradiance and wavelength upon analytical results for laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Two important results were observed and are reported here: (1) the intensity of the MS signal came to a local minimum when the laser focal point was on the sample surface, and (2) elemental fractionation based upon laser wavelength and laser pulse energy was observed. For the waste glass simulant studied, ablation with 1064-nm (IR) and 532-nm (green) radiation produced elemental fractionation that relates to the melting point of the elemental oxide, whereas with 266-nm (UV) ablation the response was independent of the elemental oxide melting point. At high laser powers, ablation at 266 nm produced an elemental bias based upon the mass of the elements. These observations suggest the use of ultraviolet radiation at low pulse energies to obtain improved analytical results.
Noise Sources in Step-Scan FT-IR Spectrometry
Authors: Manning Christopher J. , Griffiths Peter R.
Published: October 2003

Step-scan Fourier transform infrared (FT-IR) spectrometry has been accepted as a useful tool for obtaining vibrational spectra of a variety of time-dependent systems. Unfortunately, a significant signal-to-noise ratio (SNR) disadvantage has been associated with the step-scan mode of data collection relative to the same data collection time with conventional rapid-scan FT-IR spectrometry. The key difference between the two methods is the average mirror velocity, which alters the dynamic range of the detector signal, as well as the frequencies of its components. The SNR disadvantage is shown to be related to low-frequency multiplicative fluctuations, caused in part by temperature variations, which convolve noise with measured spectra. Refractive index variations of air or purge gas in the paths of the infrared- and reference-laser radiation can be a particularly serious temperature-induced problem. The various noise sources are described, and experiments confirming that some are related to temperature variations are reported.
Examination of the Photochemical Curing and Degradation of Oil Paints by Laser Raman Spectroscopy
Authors: Higuchi Seiichiro , Hamada Tosimitsu , Gohshi Yohichi
Published: October 2003

In the present study, the curing and the degradation of oil paints by irradiation with ultraviolet light was investigated by laser Raman spectroscopy. At present, the curing reaction of oil paints is interpreted by several reaction schemes, although none of them is considered to be based on definite experimental evidence. The most typical examples are as follows: one is the radical termination reaction of the crosslinking type; the other, the polymerization reaction of the Diels—Alder reaction (diene reaction) type. In the present investigation, oil paint film (ZnO White and TiO2 White) was irradiated with a Xe lamp, and the time dependence of the Raman spectra of the films was examined. It is shown that the curing reaction cannot be explained by either of the above-mentioned reaction schemes. A new reaction mechanism for the curing and the degradation of paint films is proposed. It is concluded that the microscopic approach to the elucidation of the degradation mechanism of oil paint films based on Raman spectroscopy is very useful for the improvement of oil painting techniques.
Ultraviolet 363.8-nm Raman Spectroscopic System for in Situ Measurements at High Temperatures
Authors: Yashima Masatomo , Kakihana Masato , Shimidzu Ryosuke , Fujimori Hirotaka , Yoshimura Masahiro
Published: October 2003

A new ultraviolet (UV) Raman spectroscopic system to measure the Raman scattering from materials at high temperatures up to 1500 °C has been designed. This system is based on a CW (continuous-wave) ultraviolet argon-ion laser (363.8 nm), a spatial filter, a single monochromator coupled to a double-grating rejection filter, and a two-dimensional charge-coupled device (CCD) detector. The plasma lines from the laser are almost completely rejected by a Pellin—Broca prism combined with apertures. In situ Raman measurements for a zirconia (ZrO2) specimen at various high temperatures have been performed by using the UV excitation as well as the conventional visible 488.0-nm excitation for comparison. In the case of visible excitation, thermal emission obstructs the observation of the Raman scattering from zirconia even at 900 °C; it becomes rapidly pronounced between 900 and 1100 °C, and finally it is impossible to observe Raman spectra at temperatures higher than 1200 °C. In sharp contrast to the visible excitation, the UV excitation provides good-quality Raman spectra with practically flat backgrounds for the Raman signal of tetragonal zirconia in the spectral region of 20–1100 cm−1 even at 1500 °C, and it enables clear observation of the monoclinic-tetragonal phase transformation of zirconia occurring between 1100 and 1200 °C.
Photodegradation in Ballistic Laminates: Spectroscopy and Lifetime Extension*
Authors: Renschler Clifford L. , Stallard Brian R. , White Christine A. , Garcia Manuel J. , Morse Harvey E.
Published: October 2003

Polycarbonate (PC), a critical component in ballistic laminates (BLs), is known to degrade upon exposure to ultraviolet (UV) light. For the purpose of reducing the photodegradation, a UV blocking chemical has been added to the adhesives used to join the layers of the BL. This report describes the development of a spectroscopic method for monitoring surface photodegradation of PC and the method's use in demonstrating the effectiveness of the UV blocker. Reports in the literature demonstrate that photodegradation in thin PC films may be detected by transmission infrared (IR) spectroscopy. The present work extends this approach to thick films, where small surface changes are detected by reflectance IR spectroscopy. We show that UV photodegradation of the PC surface produces a characteristic shift in the carbonyl absorption band at about 1775 cm−1. This shift is consistently observed in PC samples that have been subjected to direct artificial exposure and in PC samples that have been subjected through the outboard layers of the BL to both natural and artificial exposure. When a UV blocker is incorporated into the adhesive layers of the laminate, no peak shift is observed in the carbonyl band after the equivalent of 10 years of exposure.
Detection of 1-Hydroxypyrene as a Urine Biomarker of Human PAH Exposure Determined by Fluorescence and Solid-Matrix Luminescence Spectroscopy
Authors: Ramasamy S. M. , Hurtubise Robert J. , Weston Ainsley
Published: October 2003

A new solid-matrix luminescence method was developed for human biomonitoring that employs room-temperature fluorescence and phosphorescence for the detection and identification of 1-hydroxypyrene (1-OH-PY). Several high-performance liquid chromatography (HPLC) fractions from human urine samples were characterized by both solution fluorescence and solid-matrix luminescence. The solution fluorescence data and the solid-matrix luminescence data complemented each other. For example, in one of the fractions, the solution fluorescence showed the presence of tetrahydrotetrols of benzo[ a]pyrene. However, in this fraction, 1-OH-PY was readily detected by solid-matrix luminescence. In addition, solution fluorescence showed that 1-OH-PY was not in some of the fractions, but solid-matrix luminescence showed that 1-OH-PY was present. Solid-matrix phosphorescence was very effective in detecting 1-OH-PY in the fractions where solution fluorescence and solidmatrix fluorescence indicated that 1-OH-PY was not present. The limits of detection were in the pmol/mL range by solution fluorescence and in the subpicomole range with solid-matrix luminescence.
Identification of Cationic Herbicides in Deionized Water, Municipal Tap Water, and River Water by Capillary Isotachophoresis/On-Line Raman Spectroscopy
Authors: Walker Patrick A. , Shaver Jeremy M. , Morris Michael D.
Published: October 2003

Isotachophoresis (ITP), coupled with Raman spectroscopic detection, is used to separate and identify two cationic herbicides, paraquat and diquat, in spiked deionized water, municipal drinking water, and river water samples. On-line preconcentration is achieved with the use of field-amplified injection into a 0.03–0.1 M H2SO4 or Na2SO4 leading electrolyte solution, and isotachophoresis is achieved with the use of a 0.03–0.1 M tris(hydroxymethyl)—aminomethane (Tris) trailing electrolyte solution. The herbicides are concentrated to above 10−3 M at the detection window, allowing measurement of Raman spectra with 1-s integration windows. Spectra of the herbicides are obtained from solutions at initial concentrations in deionized water at 3.5 × 10−7 M (90 ppb) paraquat/5.8 × 10−8 M (20 ppb) diquat, from drinking water initially at 1.3 × 10−6 M (335 ppb) paraquat/1.0 × 10−6 M (360 ppb) diquat, and river water initially at 5.0 × 10−6 M (1.3 ppm) paraquat and 3.0 × 10−6 M (1.0 ppm) diquat. The utility of correlation to identify the presence of analytes and of factor analysis to recover spectra from solutions at low initial concentrations of the herbicides is demonstrated.
Multiparameter Nuclear Spectroscopic Data Acquisition and Analysis Package
Authors: Morháč Miroslav , Kliman Ján , Matoušek Vladislav , Turzo Ivan
Published: October 2003

A modular system to realize measurements along with analysis, processing, and visualization of acquired data is described. The acquisition part of the system is based on PC computer and supports several types of CAMAC crate controllers. Besides the standard algorithm, new developed algorithms of data processing have also been included in the system.
Temperature Dependence of the Mid-Infrared OH Spectral Band in Liquid Water
Authors: Iwata Tetsuo , Koshoubu Jun , Jin Chihiro , Okubo Yusei
Published: October 2003

We have studied the temperature dependence (14–57 °C) of the OH-stretching vibration band in liquid water by the use of a microscope Fourier transform infrared (FT-IR) instrument with an attenuated total reflection (ATR) cell. In order to eliminate spectral distortions, we performed Kramers–Kronig transform of the ATR spectra and derived absorption- and refractive-index spectra. The numerical values are shown in detail. Application of principal component analysis (PCA) and partial least-squares 1 (PLS 1) modeling methods to the absorption-index spectra shows that the OH band consists of two abstract spectral components. The intensity of the first component changes linearly with temperature, whereas the second component changes nonlinearly, with a turning temperature around 30 °C. Each abstract spectrum has a pair of peaks, the intensities of which vary in an inverse manner with respect to each other for the temperature change.
Bifurcation of Transversal Relaxation Rate in Emulsions
Authors: Scheurmann I. , Martín-Landrove M. , Martín R. , Espidel J.
Published: October 2003

We have performed Carr—Purcell—Meiboom—Gill (CPMG) experiments on xylene/water emulsions to understand the different molecular exchange processes present in the system. The experimental data were analyzed with a combination of nonlinear regression methods and a novel algorithm of inverse Laplace transform. The experimental results showed not only a great dispersion in the transversal relaxation rate but also a very rich branched structure of its bifurcation map. This result introduces a completely new approach and methodology to understand molecular exchange processes.
Experimental Determination of SO2, C2H2, and O2 UV Absorption Cross Sections at Elevated Temperatures and Pressures
Authors: Vattulainen J. , Wallenius L. , Stenberg J. , Hernberg R. , Linna V.
Published: October 2003

A heated and pressurized quartz cell with 150.5-mm pathlength was used to experimentally determine UV absorption spectra and further absorption cross sections of SO2, C2H2, and O2 in the wavelength range between 200 and 400 nm. Spectra were recorded at room temperature, and at 600 and 800 °C and at absolute pressures between 1 and 6 bar. A 30-W deuterium lamp was used as a light source, and the light was detected with a photomultiplier tube through a 0.4-m Czerny–Turner monochromator. Slit widths of the monochromator were adjusted to achieve a 5 Å measurement bandwidth, and the scan through the wavelength range was made in 5 Å steps. For each individual temperature and pressure level, a reference spectrum was first recorded with the cell filled with nitrogen. After this, the cell was filled with the selected species mixed with nitrogen, and the absorption spectra were recorded in similar conditions. The studied gas mixtures were calibrated to 3% accuracy.
Use of Transmitted Room-Temperature Phosphorescence to Improve Nalidixic Acid Determination
Authors: Capitán-Vallvey L. F. , Ojeda F. , Del Olmo M. , Avidad R. , Navalón A. , Vo-Denh T.
Published: October 2003

A method for nalidixic acid (NA) determination by transmitted room-temperature phosphorescence is proposed. The antibacterial agent NA in acidic solution shows native fluorescence; when NA is spotted on a filter paper precoated with β-cyclodextrin and lead (II) acetate and dried for 5 min, phosphorescence results. The transmitted phosphorescence was measured directly with the use of a homemade sample holder. The excitation and emission wavelengths were 330 and 417 nm, respectively. The applicable concentration range was between 0.06 and 4.50 μg/mL with a relative standard deviation of 2.8% and a detection limit of 0.02 μg/mL. The method was applied to the determination of NA in human urine and pharmaceuticals, with recoveries from 97.5 to 105.5%.
In Situ Measurement of Fuel in the Cylinder Wall Oil Film of a Combustion Engine by LIF Spectroscopy
Authors: Parks J. E. , Armfield J. S. , Barber T. E. , Storey J. M. E. , Wachter E. A.
Published: October 2003

Hydrocarbon emissions remain an important concern for the automotive industry due to increasingly strict regulations. In an investigation of possible emission sources within the engine, the concentration of fuel absorbed in the oil film on the cylinder wall of a small internal combustion engine has been measured with laser-induced fluorescence (LIF) spectroscopy. A laser pulse from a nitrogen laser (337.1 nm) provided the excitation, and the fluorescence was monitored with an intensifled-charge-coupled device (ICCD) array mounted to a spectrometer. The excitation laser pulse was launched through a window in the engine head onto a fiber-optic probe mounted flush with the cylinder wall. The laser-excited oil film on the fiber-optic probe produced an LIF signal that was collected by the fiber-optic probe and analyzed for fuel content. The timing of the laser pulse and ICCD gate were controlled in order to synchronize the collection of data with a particular point in the engine cycle. Measurements made in situ, while the engine was running, yield information on the amount of unburned fuel stored in the oil film for various engine conditions. Fuel-in-oil concentrations were determined for various engine temperatures during cold starts, for different fuel enrichment levels, and as a function of the crank angle of the engine cycle. Fuel concentrations as high as 50% were detected during cold starts, and fuel concentrations reached levels greater than 25% for warm engine operation. Changes in the fuel content were also found to be related to enrichment and crank angle.
Single-Molecule Detection in the Near-IR Using Continuous-Wave Diode Laser Excitation with an Avalanche Photon Detector
Authors: Soper Steven A. , Legendre Benjamin L.
Published: October 2003

While single-molecule detection in flowing sample streams has been reported by a number of groups, the instrumentation can be somewhat prohibitive for many applications due to the complexity and extensive expertise required to operate such a device. In this paper we report on the construction of a single-molecule detection device that is rugged, compact, inexpensive, and easily operated by individuals not well trained in optics and laser operations. The single-molecule detection apparatus consists of a semiconductor diode laser operating in a continuous-wave (CW) mode and a single photon avalanche diode transducer for converting the detected photons into transistor–transistor logic (TTL) pulses for displaying the data. In addition, the sampling volume is produced by a single-component lens, to create a volume on the order of 1 pL, allowing the sampling of microliter volumes of material on reasonable time scales. The device is targeted for operation in the near-IR region (700–1000 nm), where matrix interferences are minimal. Our data will demonstrate the detection of single molecules for the near-IR dyes IR-132 and IR-125, in methanol solvents in flowing sample streams at sampling rates of 100–250 samples/s. Detection efficiencies for the investigated near-IR dyes were found to be 98% for IR-132 and 50% for IR-125. Previous attempts in our laboratory to detect single molecules of IR-125 using time-gated detection were unsuccessful because of the short upper-state lifetime of this fluorophore (τf = 472 ps).
Step-Scan FT-IR Photoacoustic Studies of a Double-Layered Polymer Film on Metal Substrates
Authors: Wahls M. W. C. , Leyte J. C.
Published: October 2003

The influence of various metal substrates on the photoacoustic response of a double-layered polymer coating (polypropylene on a polybutylacrylate-adhesive) is demonstrated. The extended Rosencwaig–Gersho theory by Fernelius for a double-layered sample is used to discuss the step-scan Fourier transform infrared photoacoustic spectroscopy (FT-IR PAS) experimental results. A clear dependence of the photoacoustic phase φ on the thermal diffusivity α of the metal substrate is found. Therefore, the quality of the thermal contact between the polymer coating and the metal substrate influences the photoacoustic phase spectrum.
Highly Accurate Frequency Interpolation of Apodized FFT Magnitude-Mode Spectra
Authors: Goto Yutaka
Published: October 2003

“Generalized” interpolation (called GIα here) of fast Fourier transform (FFT) spectra apodized by a family of sinα ( X) windows has previously been proposed. The GIα gives the highly accurate interpolated frequency by calculating the simple formula of frequency determination with the use of two squared ratios between three magnitudes nearest to the peak maximum on the apodized FFT spectrum. Although the value of window parameter α, limited to integer values, has been used for the GIα, we show in the present paper that the GIα with a real α value also gives an extremely good estimate of the true frequency from the sinα ( X)-apodized spectra. Thus, we intend to apply the GIα with the optimal values of α to FFT spectra apodized by any other window functions that are often used in Fourier spectroscopy. Simulation results show that the GIα is easier and more accurate than the KCe interpolation, which uses a family of interpolating functions [ KCe(ω) = ( aω2 + bω + c)e] proposed by Keefe and Comisarow. Finally, in the presence of noise we examine effects of damping and windowing on the frequency interpolation of FFT spectra. Because damping and windowing reduce the signal-to-noise ratio (SNR), we define anew the relative SNR by the ratio of the SNR of the apodized spectrum of a damped sinusoid to the SNR of the unapodized spectrum of an undamped sinusoid. Numerical calculation shows that the relative SNR varies, owing to damping rather than windowing. In fact, the observed frequency error roughly increases as the damping ratio increases for any window functions, as is expected from our previous investigation that the frequency error based upon the GIα is inversely proportional to the SNR. However, no obvious differences between the various window functions are observed in the presence of noise.
Investigation of Light Scattering for Normalization of Signals in Laser Ablation Inductively Coupled Plasma Mass Spectrometry
Authors: Baker S. A. , Smith B. W. , Winefordner J. D.
Published: October 2003

Light scattering is evaluated for normalizing signals in laser ablation inductively coupled plasma mass spectrometry. The scattering signal produced from the transported ablation aerosol is measured with a laboratory-constructed cell. The technique is used to account for variations in the ablated mass within a matrix as well as between matrices. Matrices that are studied include brass, glass, soil, and Macor® ceramic. It is demonstrated that the technique is useful for normalizing analyte signals within a matrix; however, it is not as effective as the use of an internal standard in terms of the precision obtained. The utility of the technique to normalize between matrices is studied for glass, Macor®, and soil. The results indicate that light scattering is useful provided that the particle sizes generated are sufficiently similar.