bluuebunny/crossref_metadata_2025 huggingface dataset:
Mathematical Justification of the Use of IR Transmission Spectroscopy for the Quantitative Analysis of Surface-Treated Powders
Authors: Hanning Anders
Published: July 2005

Measuring the IR transmission through a loosely packed powder layer offers a cheap and experimentally simple method for the quantitative and qualitative analysis of surface-treated powders. It is, however, practically impossible to obtain a perfectly smooth and even powder layer—a fact that introduces large errors in the quantitative determination. To cope with this problem, one derives an equation, by means of which it is possible to carry out the determination irrespective of the layer-thickness variations. The equation is based on the use of an “internal thickness standard.” The theory is illustrated with, and supported by, a series of determinations of a silane coupling agent on a phlogopite powder. As predicted by the theory, a linear relationship is obtained when the absorbance ratio of the silane and the standard is plotted against the relative amount of silane. The quantification limit of the method lies in the monolayer range, depending on the powder surface area and the specific silane absorptivity. The method is thought to work equally well with powder mixtures.
Examination of the Matrix Isolation Fourier Transform Infrared Spectra of Organic Compounds: Part VI
Authors: Coleman W. M. , Gordon Bert M.
Published: July 2005

Matrix isolation Fourier transform spectral evidence is presented that documents the isolation of rotational isomers in an argon matrix. The spectral evidence is based on the presence of split carbonyl absorption bands in the spectra of selected derivatives of methyl acetate which do not vary in intensity with changes in the matrix-to-eluate ratios. The results compare very favorably with FT-IR data on the identical compounds obtained in the vapor phase. The low temperature of the matrix isolation experiment (10 K) allows for the observance of rotational isomers not seen at the high temperatures of the vapor-phase experiment (500 K). The presence of multiple carbonyl absorption bands dictates that careful attention must be paid to spectral/structure correlations employing MI/FT-IR data.
A Comparative Study of Rotational Temperatures in a Microwave Plasma: OH Radical versus N2+
Authors: Workman John M. , Fleitz P. A. , Fannin Harry B. , Caruso Joseph A. , Seliskar C. J.
Published: July 2005

A rotational temperature comparative study of OH radical vs. N2+ was carried out on a low-power helium microwave-induced plasma. Under the prevailing conditions, N2+ was found to provide twice as many usable lines for temperature measurement than did hydroxyl radical. For the particular torch design used, both species exhibited slightly increasing rotational temperatures at lower flow rates. At fixed conditions, OH consistently indicated higher rotational temperatures than those of the molecular nitrogen ion. Positional studies revealed a slightly increasing temperature near the center of the plasma. This work suggests that N2+ may provide a number of advantages over OH radical as a thermometric probe species in the determination of plasma rotational temperature.
Differential Thermal Lens Spectrometry Based on High-Frequency Modulation and Rotoreflective Double-Beam Configuration
Authors: Yang Yen , Hall Steven C.
Published: July 2005

A rotoreflected beam thermal lens spectrometer incorporating high-frequency modulation and the conventional double-beam concept is reported. The former enables a steady-state thermal lens to be generated, while the latter provides a means to produce a differential response that corrects for the reference absorbance automatically. The feasibility of this approach is demonstrated, and a method for improvement based on high-frequency polarization modulation is also proposed.
Space Charge Distribution in the Cathode Fall Region of an Ar Hollow Cathode Discharge
Authors: Masaki Takashi , Wada Akihide , Adachi Yukio , Hirose Chiaki
Published: July 2005

The electric field above the cathode surface of an Ar hollow cathode discharge has been measured by optogalvanic Stark spectroscopy. The field depends on the radial position of illumination and describes the radial distribution of the space charge density, ρ(r), as ρ(r) = –Ar + B, where r is the radial position and the parameters A and B are positive. The values of A and B increase with the discharge current, but the width of the cathode fall region remains nearly constant at about 1.02 ± 0.03 mm for a brass cathode of 5 mm i. d.
Analysis of Burmese and Thai Rubies by PIXE
Authors: Tang S. M. , Tang S. H. , Tay T. S. , Retty A. T.
Published: July 2005

Trace element analysis of 60 Burmese and Thai rubies by using the technique of proton-induced x-ray emission was carried out. It was found that the Burmese rubies contained higher concentrations of all impurities except iron. Our results also reveal that vanadium and iron are useful indicators for Burmese and Thai ruby attribution. The Thai rubies have high contents of iron and very low concentrations of vanadium. On the other hand, all the Burmese rubies examined contain significant amounts of vanadium, and their iron contents are, on the average, four times lower than those in the Thai rubies.
Fourier Transform Raman Spectroscopy Using a Bench-Top FT-IR Spectrometer
Authors: Parker S. F. , Williams K. P. J. , Hendra P. J. , Turner A. J.
Published: July 2005

Fourier transform Raman spectroscopy has been performed with an inexpensive bench-top FT-IR spectrometer optimized for the near-infrared. The laser excitation source was from a continuous-wave Nd: YAG laser with an output at 1.064 μm. Spectra from solid samples, ground as powders, have been obtained. Many of these are well known to fluoresce in the visible region and are thus intrinsically difficult to study by the Raman method. The FT-Raman method is described, and improvements in the technique are considered.
Characteristics of a Direct Grating Drive
Authors: Niemczyk T. M. , Gobeli G. W.
Published: July 2005

A direct-device, i.e., no sine bar, grating drive has been built and characterized. The use of a microprocessor controller allows the system to be calibrated easily. Once calibrated the system demonstrates precision and accuracy that are as good as theoretically possible given the gearing and stepper motor selected. The lack of a sine bar mechanism also allows the grating to be rotated to very high angles. Wavelength scans with the use of a single grating are demonstrated.
Fourier Deconvolution of the Amide I Raman Band of Proteins as Related to Conformation
Authors: Susi Heino , Byler D. Michael
Published: July 2005

Fourier deconvolution has been employed to enhance the resolution of the amide I Raman band of nine proteins found in milk and/or other foods. The broad band was resolved into several components. The overall shape of the amide I Raman band of proteins was found to be nearly Gaussian or to be composed of Gaussian components. A Gaussian function was therefore used for deconvolution. The results obtained were more detailed than those obtained with the Lorentzian approximation usually employed. The resolved band components were assigned to specific protein conformations. The frequencies and assignments are in good agreement with previous Raman work based on entirely different procedures. The band areas of the resolved components appear to reflect the fraction of any given conformation in a protein. Semiquantitative estimations of protein conformation are in reasonable agreement with data obtained by x-ray diffraction and by infrared methods.
Ultraviolet Resonance Raman Spectra of Escherichia Coli with 222.5–251.0 nm Pulsed Laser Excitation
Authors: Britton K. A. , Dalterio R. A. , Nelson W. H. , Britt D. , Sperry J. F.
Published: July 2005

Resonance Raman spectra of the gram-negative organism, Escherichia coli, have been obtained with 222.5-, 230.6-, and 251.0-nm excitation, and the results have been compared with those reported earlier for 242.4-nm excitation. Major changes in bacterial spectra have been observed with changes in exciting wavelength. The origins of the major peaks in each spectrum have been explained primarily in terms of contributions of nucleic acid bases and aromatic amino acids. As an aid in making assignments, spectra of aromatic amino acids, nucleosides, and mixtures of the two have been obtained at each wavelength used to excite bacterial spectra. Background fluorescence has been observed to be negligible below 251 nm. Selective excitation of bacterial nucleic acid and protein components has been done with ease. Results suggest that an extension of the exciting wavelength range to 190–220 nm will allow the selective excitation of additional cell components.
IR and/or NMR Spectra-Structure Correlations for Organophosphorus Compounds
Authors: Nyquist R. A.
Published: July 2005

IR and/or NMR spectra-structure correlations are presented which are useful in the identification of organophosphorus compounds.
Multivariate Calibration of Infrared Spectra for Quantitative Analysis Using Designed Experiments
Authors: Cahn Frederick , Compton Senja
Published: July 2005

The principal component regression (PCR) and partial least-squares (PLS) methods are used to calibrate and validate models for quantitative prediction of the composition of mixtures from FT-IR spectra. An experimental system of two- and three-component mixtures of xylene isomers was sampled with the use of statistical experimental designs. For two-component mixtures, the prediction error of independent validation samples decreased with increasing numbers of design points in the calibration. Four design points were needed to achieve a prediction accuracy of 0.0013 weight fraction. For three-component mixtures, a Scheffé {3,3} simplex lattice design, which has ten design points, achieved an equivalent accuracy of 0.002 weight fraction. There was little difference in performance between PLS and PCR computations. The results demonstrate the application of statistical methodology to the calibration of infrared spectra and show the importance of including an adequate number of samples in the calibration. The F test on the residual spectrum is shown to be a valuable tool for the identification of spurious data.
Direct Observation of a Spectral Sensitizing Dye Adsorbed to AgBr Microcrystals in a Photographic Film Containing Gelatin Using Surface Enhanced (Resonance) Raman Spectroscopy
Authors: Brandt E. S.
Published: July 2005

Surface enhanced (resonance) Raman scattering [SE(R)RS| has been used to obtain the first molecular spectra ever observed for an organic molecule within a photographic matrix containing gelatin. The molecule, l,l'-diethyl-2,2'-cyanine, is a well-known model spectral sensitizer dye. The experiment uses partial development of a photographic film to create the necessary combination of conditions favorable to SE(R)RS and fluorescence quenching that discriminate the vibrational spectrum of the dye from the background. Under these conditions, Raman signals from gelatin are not observed. Enhancement factors and detection limits are determined with the use of photographic films and several model SE(R)RS-active substrates. Electron microscopy and model substrates are used to further characterize the SE(R)RS-active sites in a photographic film.
Determination of Gaseous Formic Acid and Acetic Acid by Pulsed Ultraviolet Photoacoustic Spectroscopy
Authors: Cvijin P. Vujkovic , Gilmore D. A. , Atkinson G. H.
Published: July 2005

The quantitative determination of gaseous formic acid and acetic acid by photoacoustic spectroscopy (PAS) using pulsed laser excitation in the ultraviolet is reported. Instrumentation utilizing continuously tunable laser excitation in the 220-nm wavelength region is used to record time-resolved PA signals from samples of each acid. Detection limits of 140 ppbv for formic acid and 120 ppbv for acetic acid in dry nitrogen at one atmosphere total pressure are attained. Considerable background signal originating from atmospheric oxygen is found to impose limitations on the detection sensitivity with air samples.
Catalog of the Effects of Nonlinearity on Multivariate Calibrations
Authors: Mark Howard
Published: July 2005

A catalog of the visible effects on the data is presented, for the case when curvature (nonlinearity) of the independent variable, the dependent variable, or both exists, and when univariate, multivariate, or principal component methods are used for calibration.
Fourier Deconvolution of Infrared Rotatory Dispersion Spectra of Induced Cholesteric Phases
Authors: Heise H. M. , Kolev D.
Published: July 2005

Infrared rotatory dispersion (IRD) spectra of induced cholesteric phases resulting from solutions with liquid crystals as solvent can be used in the investigation of optically active compounds. The resolution enhancement for the so-called A-Cotton effects at the absorption bands of the originally nematic solvent by Fourier deconvolution is studied for these IRD spectra. The theoretical basis of the algorithm is discussed, and some limits are evaluated with simulated spectra. An experimental example is provided and compared with resolution enhancement by second derivatives. The application can be extended to other fields with dispersion-like spectra.
XPS Characterization of a Commercial Cu/ZnO/Al2O3 Catalyst: Effects of Oxidation, Reduction, and the Steam Reformation of Methanol
Authors: Goodby Brian E. , Pemberton Jeanne E.
Published: July 2005

X-ray photoelectron spectroscopy (XPS) is used to characterize the surface region of a commercial Cu/ZnO/Al2O3 (33/66/1 wt %) catalyst. A systematic study of the effects of oxidation, reduction, and the steam reformation of methanol on the oxidative state of the Cu component is presented. The Zn XPS features show no changes due to the various treatments. Peak fitting procedures were developed to quantitate the Cu oxidation states on the basis of the XPS Cu 2P3/2 main and satellite features. After oxidation in pure O2 at 300°C, all Cu exists as Cu+2. The Cu/Zn ratio changes from 0.28 to 0.37 as a result of this oxidation, in comparison to the ratio in the catalyst as-received. The reduction studies involved different H2/N2 mixtures (15 to 100% H2) and temperatures (250 to 300°C). The catalyst always contains Cu+1 (7.0 ± 5.0%) and Cu° (93.0 ± 5.0%) sifter reduction. The Cu/Zn ratio decreases from approximately 0.37 in the oxidized catalyst to 0.13 after reduction. After methanol-steam reformation with a 50/50 vol % mixture, the Cu 2P3/2 and Auger features are indicative of complete reduction of all Cu in the catalyst to a reduced Cu° state not seen previously. Changes in the Cu/ Zn ratio of the surface are interpreted in terms of changes in surface morphology of the Cu species.
A Theory of Electric Field and Charge Density Distributions inside a Cylindrical Hollow Cathode
Authors: Hirose Chiaki , Masaki Takashi
Published: July 2005

A simplified theory which describes the radial distributions of electric field and ion density in the cathode fall region of a cylindrical hollow cathode discharge is presented. The continuity equation for ion density and Poisson's equation for space-charge controlled field are used. An analytical form is derived on the assumptions that the drift velocity of ions obeys the high-field approximation, that the rate constant of ionization is constant over the cathode fall region, and that the radial distribution of ionizing particles (electrons or photons) is in the form which obeys Beer's law as applied to cylindrical symmetry. The application of the derived formula to the analysis of observed data of Ar hollow cathode discharges is briefly discussed.
Pentachlorodibenzo-p-dioxin Isomer Differentiation by Capillary Gas Chromatography Fourier Transform Infrared Spectroscopy
Authors: Grainger James , Reddy V. Vikram , Patterson Donald G.
Published: July 2005

Reference infrared vapor-phase spectra of the 14 pentachlorodibenzo-p-dioxin (PnCDD) isomers were recorded at low microgram concentrations. A unique infrared spectrum corresponding to each chromatographically separated or spectrally subtracted mixture component was observed. The structures for individual isomers in each isomer pair were assigned by qualitative valence-bond evaluations and empirically derived quantitative estimations of ether linkage asymmetric stretching frequencies [ vcoc(asym)] Correlations between calculated ether linkage (C-O-C) bond angles and vcoc(asym) indicate the existence of buttressed 1,6 and 1,9 nonbonded interactions not observed in tetrachlorodibenzo- p-dioxin (TCDD) isomers.
IR and/or NMR Spectra-Structure Correlations for Organonitrogen-Containing Compounds
Authors: Nyquist Richard A.
Published: July 2005

IR and/or NMR spectra-structure correlations have been developed which aid in the elucidation of molecular structure of organonitrogen-containing compounds.
The Combination of High-Resolution Molecular Fluorescence Spectroscopy with Liquid Chromatography and Thin-Layer Chromatography
Authors: Hofstraat J. W. , Gooijer C. , Velthorst N. H.
Published: July 2005

Under certain conditions, highly specific fluorescence spectra, showing molecular vibrations as in infrared spectroscopy, can be obtained for the analysis of compounds separated in TLC and microbore LC. Two techniques, both employing low-temperature solid samples, are available: Shpol'skii spectroscopy and Fluorescence Line-Narrowing (FLN) spectroscopy. The former utilizes n-alkane solvents, which form regular, crystalline solids; the latter is based on selective laser excitation. Both techniques can be applied for detection in TLC. FLN is more feasible, since the Shpol'skii method requires spraying of the TLC plate, which leads to significant spreading of the spots. FLN can also be used for offline detection in micro-LC after immobilization of the column effluent on a TLC plate. In addition, some exploratory experiments on the applicability of FLN for on-column detection in LC are presented.
Molecular Geometry Approximations for Chlorinated Dibenzodioxins by Fourier Transform Infrared Spectroscopy
Authors: Grainger James , Reddy V. Vikram , Patterson Donald G.
Published: July 2005

Reference infrared vapor-phase spectra of 15 polychlorinated dibenzodioxin- p-dioxin (PCDD) isomers were recorded at low microgram concentrations. Ether linkage (COC) bond angles for these isomers and for the 22 tetrachlorodibenzodioxin (TCDD) isomers were calculated from infrared data, with the use of mass approximations for the terminal atom in a nonlinear XY2 model and by neglecting the valence force equation symmetric stretch bending term. Calculated bond angles show a good correlation with x-ray diffraction (XRD) and carbon-13 nuclear magnetic resonance (13C NMR) relaxation results. Molecular geometries in PCDD isomers, as defined by the COC bond angle and the COC stretching frequencies, were found to range from near planar, in laterally substituted isomers with high electron withdrawing capacity aromatic rings, to tetrahedral, for isomers with low electron withdrawing capacity rings. Non-bonded interactions were also found to influence molecular geometry. Molecular geometry was used to assign structures for the 1,2,3,6,7,8- and 1,2,3,7,8,9-hexachlorodibenzodioxin isomer mixture and was found to be an important factor in estimations of COC bond strength from empirical data. Correlations between infrared data and PCDD LD50 values suggest that molecular geometry, polarizability, and steric PCDD/receptor interactions are associated with isomer toxicity.
Fiber Optic Sensing of Fluorescent Emission from Compressed Cyanine-Dye-Impregnated Fatty Acid Monolayers at the Air/Water Interface
Authors: Reichert W. M. , Bruckner C. J. , Wan Sui-Ren
Published: July 2005

Fluorescence was collected from cyanine-dye-impregnated arachidic acid monolayers at the air/water interface with the use of a fiber optics configuration and a Langmuir film balance. Fatty-acid-to-dye molar ratios in the monolayers ranged from 99:1 to 1:1. The monolayers were compressed in a step-wise manner, with sampling of cyanine fluorescence after each compression step. A drop in fluorescence intensity ranging from 20 to 80% was observed between the uncompressed and compressed monolayers. The observed fluorescence decrease appeared to be a function of barrier pressure rather than molecular area and dye concentration.
Surface Studies of the Nickel Electrode System Using a Special Transfer Cell
Authors: Sherwood Peter M. A. , Welsh Ian D. , Hercules David M.
Published: July 2005

Nickel metal with an unoxidized and an electrochemically oxidized surface can be transferred considerable distances between vacuum systems, without significant surface change, in an anaerobic cell for study by various surface science methods (XPS, Auger, ISS, and SIMS). The SIMS and ISS spectra are very sensitive to hydrocarbon contamination, which can be nearly eliminated by using the transfer cell. Complementary information is obtained using these surface analytical methods. Electrochemically oxidized nickel metal samples show the presence of oxide and hydroxide species. The results are compared with spectral data for a number of nickel compounds.
Direct Quantitation of PCB Congeners Using a Helium Discharge Detector and Internal Standard Techniques
Authors: McAteer Peter J. , Ryerson Tom B. , Argentine Mark D. , Ware Margaret L. , Rice Gary W.
Published: July 2005

Individual PCB congeners have been quantitated at ppm levels, with an average error of ±3.2%, with the use of a helium discharge detector (HDD) for element-selective detection of Cl emission. Chlorinated internal standards of known concentrations were added to each solution determined to establish the relative peak areas per unit concentration of Cl present. No detector precalibration or response factor formulations were required, since the detector response is based solely on the moles of Cl present. The same methodology was utilized to determine the % Cl in Aroclor samples without prior identification of the PCB congeners present.
FT-IR and FT-NMR Study of Organophosphorus Surface Reactions
Authors: Nadler Melvin P. , Nissan Robin A. , Hollins Richard A.
Published: July 2005

Fourier transform infrared (FT-IR) and Fourier transform nuclear magnetic resonance (FT-NMR) methods were used to examine the adsorption and reaction of diisopropyl fluorophosphate (DFP) on various solid adsorbents. Static and flow system experiments were monitored with the use of FT-IR to determine DFP adsorption rates and isotherms on silica, coated silicas, γ-alumina, coated aluminas, and activated charcoal. The adsorption of DFP(g) onto the solid adsorbents was generally very rapid, with a half-life of 20 s for 1 mg DFP onto 25 mg of 350 m2/g silica. The DFP adsorption isotherm on silica indicated chemisorption to a monolayer at P/ P0 < 0.6, followed by increased coverage that appears to be physical adsorption. Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, photoacoustic spectroscopy (PAS), and solid-state 31P NMR of adsorbed DFP showed chemisorption on silica and on alumina. Bonding at the P=O of DFP was indicated by a −41 cm−1 shift in the v(P=O) and a 1-ppm upfield shift in the 31P resonance. DRIFT, PAS kinetics, and 31P NMR showed that DFP hydrolyzed after the initial adsorption on alumina and some coated materials but not on silica or activated charcoal. The rate of hydrolysis increased on alumina with addition of water and varied with different aluminas and coated silicas.
Evaluation of a Programmable, Hardware-Driven, Isolated-Droplet Generator
Authors: Wiegand P. M. , Crouch S. R.
Published: July 2005

A progammable, high-resolution liquid-handling device, suitable for both aqueous and organic solvents, is described. This device, called an isolated-droplet generator (IDG), is based on the vibrating-capillary principle of droplet production. The unit described is capable of converting a liquid stream, such as that produced by an HPLC, to a subnanoliter-sized monodisperse droplet stream generated at rates of up to 50 kHz. Charging and deflection circuitry can be used to select individual droplets or droplet packets from the main stream. The instrument is an improvement over older designs, in that computer control imparts sufficient flexibility to make the device useful as a general-purpose high-resolution liquid-handling system. Droplet production parameters can be automatically altered to compensate for changing liquid streams, such as occur in liquid chromatography with gradient elution. The waveforms for droplet production and charging are produced entirely in hardware by a programmable counter/timer integrated circuit (IC).
Infrared and Low-Temperature Micro-Raman Spectra of the OH Stretching Vibrations in Cummingtonite
Authors: Wang A. , Dhamelincourt P. , Turrell G.
Published: July 2005

A simple structural model is developed of the effect of cation occupancy on the OH stretching bands of Cummingtonite. The observed broadening of the unresolved Raman bands at low temperatures, as well as the variation in the inter- and intra-ionic force constants of the OH group, is consistent with the model. These results confirm earlier assignments of the vibrational spectra of amphiboles in the OH stretching region.
The Use of Diffuse Reflectance Infrared Spectroscopy for Studies of Molecular Sieve Catalysis
Authors: Johnson S. A. , Rinkus R.-M. , Diebold T. C. , Maroni V. A.
Published: July 2005

Diffuse reflectance Fourier transform infrared spectroscopy (DRIFT) in conjunction with gas chromatography has been used to investigate the interaction of light hydrocarbons with the molecular sieve catalyst H-ZSM-5. Experiments were conducted in a controlled-environment (temperature, gas composition) diffuse reflectance cell interfaced with an on-line gas Chromatograph. The reactivity of CH3OH, CH3CH2OH, and CH2=CH2 on H-ZSM-5 has been investigated by observing the changes in intensity of the framework hydroxyl stretching vibrations as a function of the type of reactant, temperature, and product mix. C-H stretching vibrations of the organic fragments that form in the molecular sieve channels and pores are also observed in these experiments, and they too are correlated with reactant, temperature, and product mix with the use of spectral subtraction techniques. Important functional features of molecular sieve catalysis detectable by the DRIFT method include (1) the creation of protonated sites during calcining of the synthesis template (the process by which the catalytically active form of the sieve material is produced); (2) the labile nature of these protons as a function of reactant and temperature; and (3) the onset of coking of the molecular sieve as a result of extended use or use at higher temperatures.
Remote Near-IR Reflectance Measurements with the Use of a Pair of Optical Fibers and a Fourier Transform Spectrometer
Authors: Archibald D. D. , Miller C. E. , Lin L. T. , Honigs D. E.
Published: July 2005

A commercial near-infrared (near-IR) Fourier transform (FT) spectrometer was modified to make remote reflectance measurements over a single optical fiber or pair of optical fibers. With the use of two low-hydroxyl fused-silica optical fibers and an InSb detector, the near-IR region from 0.92 to 2.15 μm was measurable. An InGaAs detector was used to obtain reflectance spectra over the region from 0.92 to 1.56 μm. With this detector, single-fiber reflectance and transmission measurements were possible and a variety of dual-fiber probe geometries could be easily employed. Dual-fiber geometries were used to enhance pathlength, to perform depth discrimination, and to make measurements without physical contact between the probe and the specimen. Potential applications and improvements are discussed.
Deconvolution of Instrumental Broadening in Dispersive Raman Spectroscopy
Authors: Michaelian K. H. , Friesen W. I.
Published: July 2005

The resolution enhancement of instrumentally broadened Raman spectra using neon emission lines as instrument functions is considered in this paper. When the signal-to-noise ratio is sufficiently high, Fourier deconvolution is effective in reducing the instrumental broadening to the optical limit, provided that the instrument function is narrower than the individual widths of the overlapping bands. If this is not the case, a nonlinear iterative technique is required. As an example, the v1, band of CCl4 has been measured at various slit widths and deconvolved with the appropriate neon lines; for comparison, the computations have also been performed with Gaussian approximations to the true instrument functions.
A New Fiber-Optic-Based Multifrequency Phase-Modulation Fluorometer
Authors: Bright Frank V.
Published: July 2005

A new fiber-optic-based fluorescence lifetime instrument is described which is useful for the study of complex fluorescence decay kinetics. The new instrument consists of a multifrequency phase fluorometer coupled to a fiber-optic probe. To demonstrate the power of the new instrument, we show results for the unequivocal resolution of single, double, and triple exponential decays of fluorescence. In addition, spectral coverage in the ultraviolet and visible regions is possible, and lifetimes from approximately 200 ns to 150 ps are easily determined for samples as dilute as 0.1 μM.
The Steady-State and Decay Characteristics of Protein Tryptophan Fluorescence from Algae
Authors: Baek M. , Nelson W. H. , Hargraves P. E. , Tanguay J. F. , Suib S. L.
Published: July 2005

The intrinsic steady-state fluorescence due to tryptophan has been obtained from monospecific cultures of fourteen plankton algae of various genera. Fluorescence decay profiles of protein tryptophan residues were obtained for eight marine plankton algae. Each organism exhibits a strong maximum in its emission spectrum at 320–340 nm when excited at 290 nm. Iodide quenching and denaturization experiments with 8 M urea provide strong evidence for the assignment of the 320–340 nm fluorescence to protein tryptophan. Most importantly, the decay of this bacterial protein tryptophan fluorescence has been described. The observation that characteristic protein-tryptophan fluorescence lifetimes have been obtained for each organism suggests that measurements of fluorescence lifetimes may be helpful in the rapid characterization of algae. Direct application will likely be found in combination with the measurement of other luminescence parameters.
Measurement of Diffusivities of Small Molecules in Polymers Using FT-IR-ATR
Authors: Xu J. R. , Balik C. M.
Published: July 2005

A numerical method is described for obtaining diffusion coefficients ( D) of infrared-absorbing species in polymers using attenuated total reflectance infrared spectroscopy. It involves measurement of changes in the integrated intensity of diffusant infrared bands as a function of time while the diffusant moves into or out of the polymer film. The technique is illustrated with latex paint films containing a calcium carbonate extender which diffuses out of the paint films upon exposure to sulfurous acid. The values of D obtained from two different CaCO3 infrared bands were in good agreement with D obtained from independent bulk weight loss measurements. The method should be equally applicable to realtime diffusion analysis and to samples containing “frozen” concentration profiles of diffusant (as studied here). The results obtained in this preliminary study indicate that the method is probably best suited for measurement of diffusion coefficients smaller than 10−9 cm2/s.
MAGIC-LC/FT-IR Spectrometry: Preliminary Studies
Authors: Robertson R. M. , De Haseth J. A. , Kirk J. D. , Browner R. F.
Published: July 2005

A new solvent elimination interface based on the Monodisperse Aerosol Generation Interface for Combining Liquid Chromatography with Fourier transform infrared (MAGIC-LC/FT-IR) spectrometry is described. The solvent elimination efficiency of MAGIC-LC/FT-IR was studied by varying the mobile-phase composition from 100% methanol to 100% water. As the mobile-phase composition was varied, erythrosin B was injected into the interface and deposited on a KBr window after the solvent removal. Spectra were obtained which compared favorably with reference spectra, even as the mobile-phase water content was increased. A reverse-phase separation was completed to demonstrate that readily identifiable spectra can be obtained from mobile phases containing high percentages of water, without heating of the effluent stream.
Quantile BEAST Attacks the False-Sample Problem in Near-Infrared Reflectance Analysis
Authors: Lodder Robert A. , Hieftje Gary M.
Published: July 2005

The multiple linear regression approach typically used in near-infrared calibration yields equations in which any amount of reflectance at the analytical wavelengths leads to a corresponding composition value. As a result, when the sample contains a component not present in the training set, erroneous composition values can arise without any indication of error. The Quantile BEAST (Bootstrap Error-Adjusted Single-sample Technique) is described here as a method of detecting one or more “false” samples. The BEAST constructs a multidimensional form in space using the reflectance values of each training-set sample at a number of wavelengths. New samples are then projected into this space, and a confidence test is executed to determine whether the new sample is part of the training-set form. The method is more robust than other procedures because it relies on few assumptions about the structure of the data; therefore, deviations from assumptions do not affect the results of the confidence test.
Self-Absorption in Resonance Raman and Rayleigh Scattering: A Numerical Solution
Authors: Ludwig Michael , Asher Sanford A.
Published: July 2005

We have numerically calculated the parameters necessary to correct Raman intensities for self-absorption for Raman measurements utilizing a 90° scattering geometry and a cylindrical capillary sample cell. We display curves that can be used to extract these parameters for any sample absorbances at the incident laser excitation wavelength and the Raman scattered wavelength. These results make it possible, for the first time, to quantitatively utilize resonance Raman spectroscopy to determine concentrations of analytes. These parameters can also be used to numerically correct resonance Raman excitation profile measurements for self-absorption. These results clearly illustrate the dependence of spectral signal-to-noise ratios and spectral detection limits upon signal attenuation due to self-absorption.
Coincidence Profiles for Sulfur Emission at 180.73 nm (Third Order) in ICP-AES
Authors: Attar K. M.
Published: July 2005

Coincidence profiles of eleven prevalent concomitant elements, on the sulfur emission line at 180.73 nm in the third order, were procured by scanning the sulfur channel of a vacuum argon ICP-AES using the polychromator primary slit. VUV, as well as UV emission lines above 250 nm in the second order were observed, despite the fact that an interference filter with less than 2% transmission above 250 nm was located before the channel photomultiplier. Spectral interferences from Ca (1000 mg/L), Si (1000 mg/L), Cr (200 mg/L), and Ti (200 mg/L) were attributed to VUV emission lines; those from Mn (200 mg/L) to a UV line above 250 nm in the second order; and those from Fe (1000 mg/L) and V (200 mg/L) to VUV as well as UV lines. Background enhancement was exhibited by Al (1000 mg/L), Ni (200 mg/L), and Mg (1000 mg/L). Cu (200 mg/L) did not interfere. A simple procedure for distinguishing VUV from UV lines, by using the argon purge nozzle of the vacuum ICP-AES as an air optical filter, is demonstrated. The procedure is useful for facilities where a scanning monochromator is not available.
Wavelength-Resolved Single-Spark Emission Images with the Use of a Charge Coupled Device Detector
Authors: Mork Brian J. , Scheeline Alexander
Published: July 2005

With the use of charge coupled device observation technology, single spark data have shown a limitation of current sample introduction models for the high-voltage atmospheric pressure spark. Two-dimensional spatial images of wavelength-resolved data show that atomic emission varies not only in position but also in amplitude. Vapor jets are not observed, but rather nebulous clouds of emission, greatly varying in intensity, are seen.
Quantile Analysis: A Method for Characterizing Data Distributions
Authors: Lodder Robert A. , Hieftje Gary M.
Published: July 2005

Analyzing distributions of data represents a common problem in chemistry. Quantile-quantile (QQ) plots provide a useful way to attack this problem. These graphs are often used in the form of the normal probability plot, to determine whether the residuals from a fitting process are randomly distributed and therefore whether an assumed model fits the data at hand. By comparing the integrals of two probability density functions in a single plot, QQ plotting methods are able to capture the location, scale, and skew of a data set. This procedure provides more information to the analyst than do classical statistical methods that rely on a single test statistic for distribution comparisons.
Simplex Optimization of the Alternating-Current Plasma Detector for Gas Chromatography
Authors: Costanzo Robert B. , Barry Eugene F.
Published: July 2005

Several operating parameters for the alternating-current plasma detector for gas chromatography were optimized on the basis of maximization of the peak area response of the detector towards ethylmerctiry (II) chloride by the modified simplex algorithm. The parameters included in the study were the ac power output, helium make-up flow rate, column flow rate, PMT voltage, and slit width. Univariant values of the optimum were equivalent to most simplex optimum values in this study. Detector evaluation was based on the new optimized response and a new detector interface design and is compared to previous values obtained for this detector. Lower detection limits of 1.10 pg/s were realized, coupled with a relative standard deviation between 1 and 5%. Detector linearity extended over three orders of magnitude.
Soot-Ozone Reaction Kinetics: Spectroscopic and Gravimetric Studies
Authors: Smith D. M. , Welch W. F. , Jassim J. A. , Chughtai A. R. , Stedman D. H.
Published: July 2005

Studies on the kinetics of soot-O3 reactions, at various soot and ozone concentrations, have been conducted under flow conditions with ozone ranging from 50 to 15,000 ppm and soot from 2 to 350 mg. At lower concentrations, the initial rates of CO2 and CO formation are found to be half order with respect to soot and first order with respect to ozone. At higher concentrations, CO2 formation exhibits a more complex pattern. The initial rate for the formation of CO2 for a first stage is half order with respect to soot and 1.5 order with respect to O3, while the second stage is zero order in both species. Differences between data at higher and lower concentrations are discussed, and mechanisms for the formation of CO2 CO, and carboxylics during ozonation are suggested. Mass balance calculations on low concentration data reveal that only a small portion of the ozone is used to produce CO2, CO, H2O, and carboxylic species, most of it being decomposed catalytically over soot. At higher concentrations of O3 the rate of formation of carboxylic functionalities during the hexane soot-ozone reaction under static conditions has been examined. The initial rate, as determined by the Elovich equation, suggests that the soot-ozone reaction is nearly 6 times faster under equivalent conditions than the sool-NO2/N2O4 reaction reported earlier from this laboratory.
Photoacoustic Detection of Formaldehyde as a Minority Component in Gas Mixtures
Authors: Boutonnat M. , Gilmore D. A. , Keilbach K. A. , Oliphant N. , Atkinson G. H.
Published: July 2005

Concentrations of H2CO in the part-per-billion by volume (ppbv) range are determined in gaseous mixtures containing large excesses of NO2 CH3CHO, and N2 by the use of photoacoustic spectroscopy (PAS). Mixtures containing H2CO as a minority component are prepared by gas permeation methods and examined by pulsed laser PAS in the ultraviolet and visible spectral regions. The relative concentrations of the major components of each mixture are an order of magnitude or more larger than the H2CO component under study. PA spectra with 0.5-cm−1 resolution in the 302.5–303.8 nm region are presented in Fig. 3 and are used to identify spectral signatures needed for selective detection. The dependence of PA signals on concentration is determined separately for each of the three polyatomic components in samples with N2. An experimental protocol for quantitatively measuring H2CO concentrations near 50 ppbv in NO2, CH3CHO, and N2 mixtures is described.
Nondestructive Adhesive Analysis on Stamps by Fourier Transform Infrared Spectroscopy
Authors: Poslusny Matthew , Daugherty Kenneth E.
Published: July 2005

Spectroscopy has long been a popular subject with respect to postal stamps, but analysis of postal stamps has been the subject of only a few spectroscopic studies. Fourier transform infrared techniques were used in developing a nondestructive technique to analyze the adhesives on the back of stamps. This factor is of importance since the value of a stamp is partially dependent on the conditions of the original adhesive. Diffuse reflectance was finally settled on as the method of choice for this analysis, and it shows great promise not only for stamp analysis but also for other types of documentation analysis as well.
Application of CARS Spectroscopy to the Detection of SO2
Authors: Aldén Marcus , Wendt Wilhelm
Published: July 2005

Experiments have been performed to investigate the possibility of detecting low concentrations of SO2 using CARS spectroscopy. The experiments were also aimed at high-temperature investigations both in a heated cell and in a flame. During the cell measurements it was clearly revealed that the temperature has a dramatic influence on the shape of the CARS spectra, indicating a good potential for thermometry using SO2 and CARS spectroscopy.
Development of Near-Infrared Fourier Transform Raman Spectroscopy for the Study of Biologically Active Macromolecules
Authors: Lewis E. Neil , Kalasinsky V. F. , Levin Ira W.
Published: July 2005

General advantages and potential limitations of Fourier transform (FT) Raman spectroscopy using Nd:YAG laser excitation at 1064 nm have been considered for both routine analysis and specific biophysical applications. Optical design and operating parameters which affect the quality and reproducibility of the data are discussed. Moderately high resolution spectra (0.25 cm−1) of liquids are obtained with relative ease, and the results are compared with dispersive spectra. Particular emphasis has been placed on applications to biological systems where intrinsic fluorescence has traditionally limited the use of dispersive Raman spectroscopy. As an example of a biophysical study, we demonstrate the utility of FT-Raman spectroscopy in elucidating the interactions of polyene antibiotics with model membrane lipid bilayers as a means of understanding novel drug/membrane interactions at the molecular level.
The Effect of Multiplicative Scatter Correction (MSC) and Linearity Improvement in NIR Spectroscopy
Authors: Isaksson Tomas , Næs Tormod
Published: July 2005

Near-infrared (NIR) reflectance spectra of five different food products were measured. The spectra were transformed by multiplicative scatter correction (MSC). Principal component regression (PCR) was performed, on both scatter-corrected and uncorrected spectra. Calibration and prediction were performed for four food constituents: protein, fat, water, and carbohydrates. All regressions gave lower prediction errors (7–68% improvement) by the use of MSC spectra than by the use of uncorrected absorbance spectra. One of these data sets was studied in more detail to clarify the effects of the MSC, by using PCR score, residual, and leverage plots. The improvement by using nonlinear regression methods is indicated.
Molecular Orbital Study of Remote Charge Site Decompositions in the Collision-Induced Decomposition Mass Spectra of Fatty Acid Carboxylate Anions
Authors: Siegel Marshall M. , Colthup Norman B.
Published: July 2005

Molecular orbital calculations were used to study the energetics of four different mechanisms used to explain the collision-induced decomposition mass spectra of saturated fatty acid carboxylate anions produced by fast atom bombardment and chemical ionization. The most abundant homologous series of anions, terminally unsaturated carboxylate anions, arose from the concerted cleavage of gauche segments of the hydrocarbon backbone via a sixatom transition state. A series of anions of lower abundance arose by homolytic cleavage of anti segments of the hydrocarbon backbone into two radical fragments. The loss of methane from the parent anion is produced by the concerted cleavage of the terminal methyl group via a four-atom transition state. The computed activation energies for the reaction mechanisms were in the following order: sixatom transition state < four-atom transition state ≪ homolytic cleavage of hydrocarbon backbone. Dehydration of the parent anion is rationalized to occur by loss of a carboxylate oxygen and two hydrogen atoms on the alpha carbon from the carboxylate carbon.
Surface-Enhanced Raman Spectroscopy in the Near-Infrared
Authors: Chase D. B. , Parkinson B. A.
Published: July 2005

Near-infrared Raman spectroscopy has been used to obtain Surface-Enhanced Raman Spectra (SERS) of pyridine on both silver and gold electrodes. The enhancement factor is higher than that found for visible excitation, and the band intensities are somewhat different. There is no indication of photochemical damage or change of the sample when near-infrared radiation is used, even at relatively high power levels.
An Exploration Geochemical Technique for the Determination of Preconcentrated Organometallic Halides by ICP-AES
Authors: Motooka J. M.
Published: July 2005

An atomic absorption extraction technique which is widely used in geochemical exploration for the determination of Ag, As, Au, Bi, Cd, Cu, Mo, Pb, Sb, and Zn has been modified and adapted to a simultaneous inductively coupled plasma-atomic emission instrument. The experimental and operating parameters are described for the preconcentration of the metals into their organometallic halides and for the determination of these metals. Lower limits of determination are equal to or improved over those for flame atomic absorption (except Au), and ICP results are very similar to the accepted AA values, with precision for the ICP data in excess of that necessary for exploration purposes.
Ultra-Trace-Level Determination of Cobalt, Chromium, and Hydrogen Peroxide by Luminol Chemiluminescence Detected with a Charge-Coupled Device
Authors: Jalkian Rafi D. , Denton M. Bonner
Published: July 2005

A solid-state two-dimensional charge-coupled device (CCD) is used to detect the chemiluminescence of luminol with hydrogen peroxide and a transition metal ion. The chemiluminescence spectra are recorded with the use of trace amounts of metal ions. Excellent linearity, dynamic range, and detection limits are obtained for the total amount of Cr3+, Co2+, and H2O2 analyzed by manual injection. Detection limits on the order of low femto-mole levels of analytes are reported. The utility of CCDs for ultra-low-level light measurements is discussed, and new concepts for “luminometers,” both wavelength dispersive and nondispersive, are described.
Fourier Transform Infrared Analysis of Evolved Gases: Determination of Activation Energies
Authors: Sanchez Luis Antonio , Keating Mimi Y.
Published: July 2005

The use of Fourier transform infrared evolved-gas analysis (FT-IR/EGA) to determine activation energies from the heating rate dependency of the maximum evolution of effluent is demonstrated. The mathematical considerations are similar to those normally applied to differential thermal analysis. The determination of the activation energy is substantiated with dehydration of calcium oxalate monohydrate during pyrolysis; the results are compared with thermogravimetry analysis results, and indicate that the activation energy in the dehydration step in the pyrolysis of calcium oxalate monohydrate is temperature dependent.