bluuebunny/crossref_metadata_2025 huggingface dataset:
Calibration Transfer in the Automated Detection of Acetone by Passive Fourier Transform Infrared Spectrometry
Authors: Koehler Frederick W. , Small Gary W. , Combs Roger J. , Knapp Robert B. , Kroutil Robert T.
Published: October 2003

The qualitative determination of acetone is performed by passive Fourier transform infrared (FT-IR) spectrometry with data spanning two spectrometers. Digital filtering and piecewise linear discriminant analysis techniques are optimized and applied directly to short interferogram segments to eliminate background and instrument variation and then perform pattern recognition. Once optimized, this methodology classifies remote sensing data into categories representing the presence or absence of the analyte in an automated fashion. The addition to the training set of small numbers of interferogram data from a second spectrometer is evaluated in the creation of qualitative models robust with respect to differences between the instruments. Results of these experiments show that classification percentages averaged across all tested interferogram segments are improved from 76.2 ± 6.4% to 95.1 ± 2.2% with the addition of as few as 10 background interferograms collected in the field with the secondary instrument. The results also demonstrate that a broader, more optimal range of segments in the interferogram can be utilized when these background data are added from the secondary instrument. It is also found possible to standardize the data from the secondary instrument with blackbody background interferograms collected in the laboratory.
Near-Infrared Spectroscopy for Monitoring the p-Diethylbenzene Separation Process
Authors: Chung Hoeil , Ku Min-Sik , Lee Jaebum , Choo Jaebum
Published: October 2003

Near-infrared (NIR) spectroscopy has been successfully used for the monitoring of important components in the p-diethylbenzene (PDEB) separation process. The process is composed of mostly diethylbenzene isomers ( ortho, meta, and para) and extractant ( p-xylene), as well as other C9–C11 aromatic hydrocarbons. Therefore, the major concern in using NIR spectroscopy in this process was the spectral resolution of NIR spectra among diethylbenzene isomers, since the molecular structures of each isomer were very similar. NIR spectral features of o-diethylbenzene (ODEB), m-diethylbenzene (MDEB), and PDEB showed considerable spectral differences in the 2100–2220 nm range. These combination bands originated from the combination of the =C–H stretch at 3100–3000 cm−1 and C=C ring stretch at 1600–1450 cm−1. Characteristic C=C ring stretches of each isomers in the IR region result in selective and identifiable spectral features in the NIR region. Partial least-squares (PLS) regression was used to build each calibration model for ODEB, MDEB, PDEB, and p-xylene (PX). PLS calibration results of the four components showed excellent correlation with gas chromatography data. The combination region (2100–2500 nm) provided the important isomeric spectral information for PLS calibration since the absorption bands in this region were the most sensitive and selective.
Resolution of the NMR Spectrum Using Wavelet Transform
Authors: Shao Xueguang , Gu Hua , Wu Jihui , Shi Yunyu
Published: October 2003

A novel method for resolution of an overlapping nuclear magnetic resonance (NMR) spectrum using the wavelet transform (WT) is proposed. Due to the localization character in terms of both space and scale of the wavelet transform, an NMR spectrum can be decomposed into a series of localized contributions (details and approximations) at different resolution levels, which represent the spectral information of different resolutions. With amplification of the contributions at fine resolution level and then reconstruction (inverse transform), the resolution of the reconstructed NMR spectrum will increase. Therefore, the resolved spectrum can be obtained from a low-resolution spectrum or an overlapping spectrum. Simulated data sets and a spectrum of a biological sample (gramicidin-S) were investigated by this method. It was proven that resolution of NMR spectra can be greatly improved by this approach.
Chemical Analysis with a Low-Resolution Raman Spectrometer
Authors: Mann Charles K. , Vickers Thomas J.
Published: October 2003

The performance of a very compact and low-cost Raman system has been examined in detail. We have attempted to use it for both qualitative identifications and quantitative analyses of mixtures. As a part of the evaluation, we have attempted to devise compensation routines when these were needed. We conclude that this system can be used for a limited range of qualitative applications, but that the quantitative performance is inadequate. The principal problems originated in laser fluctuations and in the appearance of spectral artifacts when the laser was operated.
Study of Solution Calibration of NIST Soil and Glass Samples by Laser Ablation Inductively Coupled Plasma Mass Spectrometry
Authors: Bi Melody , Ruiz M. Antonio , Smith Benjamin W. , Winefordner James D.
Published: October 2003

A method for the determination of trace element concentrations by laser ablation inductively coupled plasma mass spectrometry (ICP-MS) using solution calibration and an internal standard has been studied and evaluated by analyzing NIST soil and glass samples. In most cases, the measured element concentrations were within ±10% of the certified values. The internal standard was chosen on the basis of investigations of the proper signal intensity of certain isotopes and the homogeneity of their distribution in the sample. For soil samples, a matrix element, Mg, was chosen to be the internal standard. For glass samples, a trace element, Sr, was used as the internal standard. The results indicated that in both cases the internal standard was effective. Ni and Cu in soil gave poor results, while good results were obtained for Ni and Cu in glass samples. Time-resolved studies show that Ni gave many more signal spikes than other elements when the ablating laser moved across the surface of the soil sample. This observation indicates that one possible reason for the poor results was caused by the heterogeneity of the Ni distribution in the matrix.
Emission Spectroscopic and Mass Spectrometric Characterization of Laser-Ablated Species from a Ferroelectric SrBi2Ta2O9 Target
Authors: Li Yi , Yang Xinju , Tang Yongxin , Qin Qizong
Published: October 2003

The ablation of a SrBi2Ta2O9 (SBT) target under 355 nm laser irradiation has been investigated with an angle- and time-resolved quadrupole mass spectrometric technique. Mass and angular distributions of ionic and neutral ablated species are measured. The observed major ablated species include metal atoms and ions as well as binary metal oxides. The time-of-flight (TOF) spectra of ablated species such as Bi and SrO are measured and can be well fitted by a Maxwell–Boltzmann distribution with a stream velocity. The estimated kinetic energies of metal ions are found to be much higher than those of neutral species. The angular distributions of ablated species show that ionic and neutral species ejected within a coneshaped plume can be simulated by cos nθ and acosθ + bcos nθ functions, respectively. The optical emission spectroscopic technique is also employed in order to examine the electronically excited SrO, TaO, and BiO, in which BiO is not observed in mass spectroscopy. The dependence of the concentrations of metal oxides on the pressure of ambient oxygen provides helpful information for the growth of SBT thin films.
Investigations into Trace Detection of Nitrocompounds by One- and Two-Color Laser Photofragmentation/Fragment Detection Spectrometry
Authors: Swayambunathan Vaidhianat , Sausa Rosario C. , Singh Gurbax
Published: October 2003

Trace concentrations of nitrogen dioxide (NO2), nitromethane (CH3NO2), and 2,4,6-trinitrotoluene (TNT) are detected by both one- and two-color laser photofragmentation/fragment detection (PF/FD) spectrometry using one or two lasers. The PF/FD methods studied are (1) one-laser, one-color photofragmentation of the analyte molecule at 227 or 454 nm with subsequent detection of the characteristic nitric oxide (NO) photofragment by one- or two-photon laser-induced fluorescence using its A2Σ+ –X2π (0,0) transitions near 227 nm; (2) one-laser, two-color PF/FD, where a 355 nm laser beam is used for additional analyte photofragmentation and NO is detected by both one- and two-photon LIF as in the previous case; (3) two-laser, two-color PF/FD, where the pump and probe beams are time delayed; and (4) one-laser, one-color PF/FD at 355 nm, where the 355 nm beam photofragments the target molecule and the prompt emission from electronically excited NO (A2Σ+) is monitored in the range of 200–300 nm. PF/FD excitation and emission spectra are recorded and also simulated with the use of a computer program based on a Boltzmann distribution analysis with transition probabilities, rotational energies, and rovibrational temperatures as input parameters. The effects of laser wavelength, laser pump energy, time delay between pump and probe beams, and analyte concentration on PF/FD signal are investigated and reported. Limits of detection [signal-to-noise (S/N) = 3] for the nitrocompounds range from low ppbv to ppmv for 10 s integration time and laser energies of ∼ 5 mJ and 100 μJ for the pump and probe beams, respectively. These results are presented and compared to other PF/FD methods for nitrocompound monitoring.
Determination of Chromium in Human Lung Fibroblast Cells Using a Large Bore—Direct Injection High-Efficiency Nebulizer with Inductively Coupled Plasma Mass Spectrometry
Authors: McLean John A. , Acon Billy W. , Montaser Akbar , Singh Jatinder , Pritchard Daryl E. , Patierno Steven R.
Published: October 2003

A novel method for the determination of chromium in suspensions of human lung fibroblast cells is described by using a large bore–direct injection high efficiency nebulizer (LB-DIHEN) with micro-scale flow injection analysis and inductively coupled plasma mass spectrometric detection. Chromium(VI)-treated cells were first counted and then suspended in a phosphate buffer saline solution. With the use of the method of standard additions, the relative concentration of Cr in ∼ 100 HLF cells/peak was determined at m/z = 50. Because the cells tend to clump and can yield inhomogeneities in the total number analyzed, Mg was used as an internal standard to compensate for the total cell mass. The level of Cr in HLF cells grown in a medium of 100 μM Na2CrO4 for two hours is on the order of 180 fg Cr/cell after correction for the number of cells in each injection.
Direct Evidence of Ozone as the Active Oxidant in “Photooxidation” of Alkanethiols on SERS-Active Silver
Authors: Ferris Matthew M. , Rowlen Kathy L.
Published: October 2003

Surface-enhanced Raman spectroscopy (SERS) has been used to study the mechanism of “photooxidation” of decanethiol self-assembled on roughened Ag. Direct exposure of self-assembled decanethiol to light from a low-pressure Hg lamp under ambient conditions results in adsorbed oxidized sulfur species. Absorbance spectroscopy was used to quantify ozone levels (∼ 20 ppm) generated by the Hg lamp. When decanethiol samples were exposed to the same amount of 254 nm light from the lamp but were environmentally isolated, so that oxygen was present but ozone generated by the lamp could not diffuse to the surface, no oxidation was observed. In addition, when decanethiol samples were exposed to an equivalent amount of electrically generated ozone in the absence of light, the SERS oxidation product spectra were identical to those generated by the lamp under ambient conditions. Quantitative investigation of the kinetics of oxidation yielded second-order rate constants of 0.0029 ± 0.0005 ppm−1 s−1 and 0.0024 ± 0.0006 ppm−1 s−1, for electrically generated ozone and the lamp, respectively. The two rate constants are the same within error, indicating that under the conditions of our experiment the mechanism of oxidation is dominated by ozone and not light.
Solid-Phase Luminescence of Several Rare Earth Ions on Ion-Exchange Films
Authors: Tanner Stephen P. , Street Kenneth W.
Published: October 2003

The development and characterization of a novel ion-exchange film for solid-phase fluorometry and phosphorimetry is reported. This new cation-exchange material is suitable for spectroscopic applications in the ultraviolet and visible regions. It is advantageous because it, as a single entity, is easily recovered from solution and mounted in the spectrofluorometers. After preconcentration on the film, the luminescence intensity of lanthanide ions is several orders of magnitude greater than that of the corresponding solution, depending on the volume of solution and the amount of film. This procedure allows emission spectral measurements and determination of lanthanide ions at solution concentrations of < 5 μg/L. The film may be stored for subsequent reuse or as a permanent record of the analysis. The major drawback to the use of the film is slow uptake of analyte due to diffusion limitations.
Mid-IR Spectroscopy for the Quantification of Metal Ions in Aqueous Solution in the Nanogram Range
Authors: Pérez-Ponce Amparo , Lendl Bernhard
Published: October 2003

A novel mid-infrared (IR) flow-through sensor system for the determination of metal ions in aqueous solution was developed. The flow-through sensor comprised weak cation exchanger beads (Sephadex with carboxylic acid moieties) placed in the optical path of a 37 μm IR transmission cell. The combination of the flow-through sensor with a sequential injection analysis (SIA) system allowed us to carry out the whole analysis procedure including analyte–sensor interaction and sensor regeneration, as well as data acquisition, under computer control. The first step of an analysis sequence was regeneration of the flow-through sensor by rinsing with diluted (0.012 M) hydrochloric acid followed by distilled water, thus protonating the carboxylic acid moieties. Then, after acquisition of a background spectrum and pumping 500 μL of sample followed by 1000 μL of distilled water through the flow-through sensor, the sample spectrum was recorded. Upon passage of the sample, the metal ions were retained on the cation exchanger, giving rise to spectral changes mainly resulting from the exchange of the protons by metal cations. It was found that the spectral changes were characteristic for the metal cations investigated. This observation was exploited to construct a multivariate calibration model for the simultaneous determination of calcium and magnesium ions in water. The developed method covered the range from 0 to 200 nmol for each cation (root mean square error of cross-validation: 9.2, and 7.6 nmol for Ca2+ and Mg2+, respectively) and was successfully applied to the determination of the water hardness of the tap water in our laboratory.
Characterization of Plant Carbohydrates and Changes in Leaf Carbohydrate Chemistry Due to Chemical and Enzymatic Degradation Measured by Microscopic ATR FT-IR Spectroscopy
Authors: Mascarenhas Marcella , Dighton John , Arbuckle Georgia A.
Published: October 2003

Leaf litter decomposition is largely effected by the enzymatic action of fungal colonizers of leaf material. Microscopic attenuated total reflectance (ATR) infrared spectroscopy would be a useful tool to evaluate changes in leaf litter carbohydrate chemistry over time during the colonization process at the scale of resolution of the fungal hyphae. This paper reports the first studies to use microspectroscopy in the mid-infrared (IR) region to perform analyses within an area of 250 × 250 μm to gain spectra of single species of sugars and complex carbohydrates (cellulose, hemicellulose, lignin) to identify characteristic IR reflectance peaks and to be able to separate the species in complex media. Changes in leaf surface carbohydrate chemistry were interpreted from spectra obtained from leaf material that underwent the following: (1) treatment with acetone (to remove surface waxes), (2) treatment with enzymes, and (3) observation after colonization by fungi. Analysis of spectra obtained from random locations or from the same points on the leaf surface over time permitted changes in carbohydrate chemistry to be detected. Comparative analysis of spectra was carried out by using time-series analysis of variance of selected characteristic peak heights and multivariate statistics.
Preliminary Studies of the Characteristics and Factors Influencing the Emission from a Copper Vapor Laser-Induced Plasma
Authors: Aucélio R. Q. , Castle B. C. , Smith B. W. , Winefordner J. D.
Published: October 2003

The interaction between a laser beam from a high-repetition-rate copper vapor laser (CVL) and a metal target was studied. The influence of several buffer gases and their pressure on the generation of the plasma was evaluated, and the importance of the presence of air on the process of the plasma formation was observed. Diagnostics of the plasma were made. Several parameters were optimized in order to maximize the emission intensity of the 327.75 nm line of the copper target. Temporal studies were performed in order to observe the evolution of the signal-to-background ratio.
Cross-Correlation Analysis on the Resonant Voigt-Effect Spectra of Magnetic Field-Induced Transitions in the Oxygen a Band
Authors: Muroo Kazuyuki , Iwasaki Hisao , Suzuki Kouji , Takubo Yoshitaka
Published: October 2003

We applied the cross-correlation analysis to the resonant Voigt-effect spectroscopy of the magnetic field-induced transition in the oxygen A band b1 Σ g+ ( v' = 0)– X3 Σ g− ( v = 0). By calculating the cross-correlation function of the experimental profile by using the theoretical profile of the field-induced line, we detected a field-induced line superimposed on a magnetic dipole-allowed line with a larger intensity. The improvement of detection sensitivity for the isolated lines is also described.
Speciation of Uranium by Electrospray Ionization Mass Spectrometry: Comparison with Time-Resolved Laser-Induced Fluorescence
Authors: Moulin C. , Charron N. , Plancque G. , Virelizier H.
Published: October 2003

Speciation of actinides, lanthanides, and fission products is a major challenge in the framework of nuclear fuel cycle studies. Electrospray–mass spectrometry has been used for uranium speciation. Free uranyl (UO22+), the first hydroxo complex (UO2OH+), and the oligomeric species (UO2)3(OH)5+ have been observed as a function of pH. Different aqueous solvents (sodium perchlorate, perchloric acid/ammonium acetate, and perchloric acid/ammonia) were tested in order to limit the presence of adducts. The influence of various parameters such as the cone voltage, temperature, and gas flow rate is presented. Comparison with results obtained by time-resolved laser-induced fluorescence on the same solutions shows a similar tendency despite a slight shift in pH relative to the OECD database.
Recursive Maximum Entropy Algorithm and its Application to the Luminescence Lifetime Distribution Recovery
Authors: Vinogradov Sergei A. , Wilson David F.
Published: October 2003

A simple algorithm, based on recursive quadratic optimization, is suggested for the numerical inversion of integral transforms. The algorithm was found particularly useful for “small scale” problems, with the number of independent parameters ranging between 100 and 200. The programming, parameterization, and performance of the algorithm are discussed, as well its application to the analysis of time-resolved luminescence data.
Temperature-Independent Pressure-Sensitive Paint Based on a Bichromophoric Luminophore
Authors: Ji Hai-Feng , Shen Yibing , Hubner J. Paul , Carroll Bruce F. , Schmehl Russell H. , Simon Jerald A. , Schanze Kirk S.
Published: October 2003

A spectroscopic study is presented of a pressure-sensitive paint (PSP) formulation that consists of the bichromophoric luminophore, Ru-pyrene, dispersed in an acrylate co-polymer matrix (MPP, a 1:1 co-polymer of poly(ethylene glycol)ethyl ether methacrylate and tri(propylene glycol) diacrylate). The Ru-pyrene molecule contains Ru(bpy)32+ and pyrene chromophores covalently linked together. The luminophore features a very long-lived emission (τ ⋍ 50 μs) that makes it ideal for incorporation into luminescent oxygen sensor coatings. Stern–Volmer calibrations were carried out on the Ru-pyrene/MPP PSP as a function of temperature over the range from 25 to 55 °C. The calibrations indicate that the Stern–Volmer constant ( Ksv) for the Ru-pyrene/MPP PSP is temperature independent ( Ksv 4.5 atm(air)−1). By contrast, a PSP consisting of meso-tetra-kis-(pentafluorophenyl)porphyrin platinum(II) in MPP exhibits strongly temperature dependent Ksv, demonstrating that the unique temperature dependence of the Ru-pyrene/MPP PSP arises from the combined properties of the Ru-pyrene luminophore and the MPP matrix; i.e., it is not a special property of the MPP matrix alone. Analysis of luminescence decay lifetime data indicates that the temperature-independent Ksv in the Ru-pyrene/MPP PSP arises because the nonradiative decay rate of the Ru-pyrene chromophore varies moderately with temperature. The temperature-dependent nonradiative decay rate is believed to arise due to a thermally activated intramolecular energy transfer process in Ru-pyrene.
Unique Oxygen Analyzer Combining a Dual Emission Probe and a Low-Cost Solid-State Ratiometric Fluorometer
Authors: Kostov Yordan , Van Houten Kelly A. , Harms Peter , Pilato Robert S. , Rao Govind
Published: October 2003

A new oxygen analyzer combining a polymer-encapsulated dual-emission probe and a diode-based ratiometric fluorometer is described. The ratiometric fluorometer was configured to measure the relative fluorescence and phosphorescence intensity of the short-lived singlet and long-lived oxygen-quenchable triplet of [(dppe)Pt{S2C2(CH2CH2–N–2-pyridinium)}](BPh4), where dppe is 1,2- bis(diphenylphosphino)ethane. This luminescent dye was immobilized at 0.3% by weight in cellulose acetate/75% triethylcitrate and cast into a 0.5 mm-thick film. The dye molecule was excited with a blue light-emitting diode (LED) and the singlet and triplet emissions monitored by individual photodiodes at 570 and 680 nm, respectively. Oxygen can be accurately measured without interference from nonanalyte-induced intensity changes by monitoring the relative output of the two photodiodes. The output of the device was linear with oxygen concentration. The PO2(1/2) from the ratio-adapted Stern–Volmer plot was 9.6% oxygen (≈73 torr), offering a dynamic range of 0–90% O2. The device is stable and the oxygen measurements reproducible. Intentional photobleaching of ≈20% of the sensor dye had little effect upon the reproducibility of the oxygen measurements.
Photodeposition of Diffraction Gratings in Glass: A Comparison of Lithographic, Laser Writing and Holographic Deposition
Authors: Sunil D. , McQuade Arthur W. , Ye Gouzhang , Gafney Harry D.
Published: October 2003

High-resolution holographic gratings with line spacings ranging from 8 to 50 μm have been achieved by 488 nm photolysis of porous glasses impregnated with Fe(CO)5. The interference pattern created with a Mach–Zehnder interferometer and Ar+ laser creates a pattern of well-resolved, parallel regions possessing a refractive index and optical density different from those of the bulk glass. Line spacings were calculated from the diffraction of a He–Ne laser and corroborated by optical microscopy. Comparing the optical performance of gratings prepared holographically with those produced by direct laser writing or photolithography establishes significant improvements in the uniformity of the deposited gratings and optical performance. Thermal consolidation of the porous glass at 1200 °C decreases sample volume and line spacing in direct proportion to the decrease in the dimension perpendicular to the grating lines. Consolidation not only improves optical performance by reducing line spacing, but encapsulates the grating within the glass matrix, thereby creating a grating that is unaffected by high laser powers, insensitive to UV excitation, and stable under a variety of environmental and chemical conditions.
Reflectance Study of Pigment Slurries
Authors: Peiponen Kai-Erik , Jääskeläinen Anssi , Räty Jukka , Richard Olivier , Tapper Unto , Kauppinen Esko I. , Lumme Kari
Published: October 2003

Optical properties of nonabsorbing turbid slurries were studied by reflectometric techniques. Two types of industrial slurries were investigated. The one slurry contained spherical plastic pigments, whereas the other consisted of irregularly shaped calcium carbonate particles in water. The refractive index of the plastic pigment particle was calculated, with the aid of a light-scattering model, as a function of wavelength by using reflectometric data. In addition, the effective refractive index of the plastic pigment slurry was obtained with the use of a surface plasmon resonance sensor. Although analysis of reflectometric data for calcium carbonate slurries is cumbersome, it was possible to obtain information about the volume concentration of optically birefringent particles in water.
Multianalyte Serum Assays from Mid-IR Spectra of Dry Films on Glass Slides
Authors: Shaw R. Anthony , Mantsch Henry H.
Published: October 2003

An analytical method based upon mid-infrared spectroscopy is proposed, and the advantages of this approach are discussed. The method involves drying a liquid specimen to a film, and deriving analyte levels from the infrared spectrum of that film. The specific aim of this study was to determine whether glass might serve as a suitable substrate for the simultaneous determination of several analytes in complex mixtures. Using human serum as a “proof-of-concept” example, we show here that six commonly measured analytes may be determined from spectra originally measured by employing barium fluoride substrates, but restricting the analytical models to absorptions within the region 2000–4000 cm−1—i.e., making use of only those absorptions that are accessible with glass substrates. With the use of partial least-squares calibration models, it is shown that albumin, cholesterol, glucose, total protein, triglycerides, and urea may be determined with standard errors that approach or meet the criteria required for routine clinical analysis. The practical advantages of such an approach are discussed.
Aprotic Solvent Effects upon the Fundamental Vibrational Peak of the Nitrile Group in Benzonitrile
Authors: Kolling Orland W.
Published: October 2003

The characteristic IR peak at 2230 cm−1 (298 K) for the C=N group in benzonitrile shows a modest shift with changing solvent. A solvent reaction field model (SCRF-MO) perturbation model applied earlier to carbonyl species was tested with the Vmax(C=N) data for aprotic nonpolar, aprotic dipolar, aprotic highly dipolar, and aromatic liquids. For all the dielectric continuum functions tested as components in that model, there is evidence that solvent dipolarity and solvent polarizability are responsible for the nitrile band shift. However, as a solvent class, the aromatics exhibit a greater perturbation in Vmax(C=N) than predicted by any of the continuum descriptions.
Species Identification in Selected Raw Homogenized Meats by Reflectance Spectroscopy in the Mid-Infrared, Near-Infrared, and Visible Ranges
Authors: Downey Gerard , McElhinney John , Fearn Tom
Published: October 2003

Mid-infrared (2000–800 cm−1), near-infrared (750–2498 nm), and visible (400–750 nm) reflectance spectra of 230 homogenized meat samples (chicken, turkey, pork, beef, and lamb) were collected. Species identification was attempted by using factorial discriminant analysis (FDA), soft independent modeling of class analogy (SIM-CA), K-nearest neighbor (KNN), analysis and discriminant partial least-squares (PLS) regression. A variety of wavelength ranges was investigated for optimum accuracy. Particular difficulty was encountered in distinguishing between chicken and turkey; models were therefore developed with the use of five separate meat classes and again with the use of four, with chicken and turkey samples being treated as one group. Discriminant PLS, FDA, and KNN models provided similar levels of accuracy in this application. Correct classification rates in excess of 90% were achieved in all cases.
N2 CARS Thermometry within the Outer Jacket of a Metal Halide Lamp
Authors: Brock L. R. , Adler H. G.
Published: October 2003

We applied high-resolution coherent anti-Stokes Raman spectroscopy (CARS) to measure the gas temperature at a number of points within the nitrogen-filled outer jacket of a 360 W metal halide lamp. A comparison between the measured rotationally resolved N2 CARS spectra with spectral simulations collected between 500 and 1000 K allowed the temperature at each point in the lamp to be determined. In addition to demonstrating the diagnostic power of the CARS technique in a high-intensity discharge lamp, a comparison of the measured temperatures to calculated axial and radial temperature profiles was achieved. Good agreement between the theoretical and experimental temperature profiles was attained.
Stand-off Detection of Chemicals by UV Raman Spectroscopy
Authors: Wu Ming , Ray Mark , Fung K. Hang , Ruckman Mark W. , Harder David , Sedlacek Arthur J.
Published: October 2003

Experimental results are reported on a mobile, stand-alone, solar-blind ultraviolet (UV) Raman lidar system for the stand-off detection and identification of liquid and solid targets at ranges of hundreds of meters. The lidar is a coaxial system capable of performing range-resolved measurements of gases and aerosols, as well as solids and liquids. The transmitter is a flash lamp pumped 30 Hz Nd:YAG laser with quadrupled output at 266 nm. The receiver subsystem is comprised of a 40 cm Cassegrain telescope, a holographic UV edge filter for suppressing the elastic channel, a 0.46 m Czerny–Turner spectrometer, and a time gated intensified charge-coupled device (CCD) detector. The rejection of elastic light scattering by the edge filter is better than one part in 105, while the transmittance 500 cm−1 to the red of the laser line is greater than 50%. Raman data are shown for selected solids, neat liquids, and mixtures down to the level of 1% volume ratio. On the basis of the strength of the Raman returns, a stand-off detection limit of ∼ 500 g/m2 for liquid spills of common solvents at the range of one half of a kilometer is possible.
Combination of Micro-PIXE with the Pattern Recognition Technique for the Source Identification of Individual Aerosol Particles
Authors: Guo P. , Wang J. , Li X. , Zhu J. , Reinert T. , Heitmann J. , Spemann D. , Vogt J. , Flagmeyer R.-H. , Butz T.
Published: October 2003

In order to identify the sources of individual aerosol particles, we developed an identification system based on the combination of the micro-PIXE (particle-induced X-ray emission) technique with the pattern recognition (PR) technique. It uses the micro-PIXE spectrum of an individual aerosol particle as its fingerprint to identify the origin of the particles. A total of 294 micro-PIXE spectra of individual aerosol particles, collected at Shanghai City in China, were applied to test the PR system. These particles were collected from several pollution sources and a local environment monitor site. Most of the environment particles were identified, and the most probable sources were assigned by the PR system. It was found that cement factories and vehicle exhaust are the major contributors. About 14% of the particles from the environment monitor site could not be identified by their spectra. They might have come from some other sources we have not yet investigated. The validity and the efficiency of the system are evaluated and discussed. It is demonstrated that the combination of micro-PIXE with the pattern recognition technique offers a new, powerful tool for the source identification of individual aerosol particles.
Speciation Model Selection by Monte Carlo Analysis of Optical Absorption Spectra: Plutonium(IV) Nitrate Complexes
Authors: Berg John M. , Veirs D. Kirk , Vaughn Randolph B. , Cisneros Michael R. , Smith Coleman A.
Published: October 2003

Standard modeling approaches can produce the most likely values of the formation constants of metal–ligand complexes if a particular set of species containing the metal ion is known or assumed to exist in solution equilibrium with complexing ligands. Identifying the most likely set of species when more than one set is plausible is a more difficult problem to address quantitatively. A Monte Carlo method of data analysis is described that measures the relative abilities of different speciation models to fit optical spectra of open-shell actinide ions. The best model(s) can be identified from among a larger group of models initially judged to be plausible. The method is demonstrated by analyzing the absorption spectra of aqueous Pu(IV) titrated with nitrate ion at constant 2 molal ionic strength in aqueous perchloric acid. The best speciation model supported by the data is shown to include three Pu(IV) species with nitrate coordination numbers 0, 1, and 2. Formation constants are β1 = 3.2 ± 0.5 and β2 = 11.2 ± 1.2, where the uncertainties are 95% confidence limits estimated by propagating raw data uncertainties using Monte Carlo methods. Principal component analysis independently indicates three Pu(IV) complexes in equilibrium.
Fast LIF Approach to NO Rotational Temperature and Density Measurement: Application to a Gas-Dynamic Expansion
Authors: Dilecce G. , Simek M. , Vigliotti M. , De Benedictis S.
Published: October 2003

An excitation–detection laser-induced fluorescence (LIF) scheme is proposed for the measurement of the NO rotational temperature and density. It is based on the simultaneous excitation of three NO ro-vibronic transitions from only two—one low and one high—J-rotational levels, with the laser set at a suitable fixed wavelength. The procedure does not require the measurement of the excitation spectrum but only of a well-resolved small spectral region of the fluorescence spectrum. The temperature and the density measurements are based on a reference NO LIF spectrum obtained at a known pressure and temperature that is used as a standard. This method is easy and not time consuming. It has been applied to a gas-dynamic expansion.
Two-Dimensional Correlation Spectroscopy: Effect of Band Position, Width, and Intensity Changes on Correlation Intensities
Authors: Czarnecki Mirosław A.
Published: October 2003

Simulation studies have demonstrated that the effect of a band shift may be completely removed from two-dimensional (2D) synchronous spectra if a shifting band simultaneously changes its intensity. In contrast, the corresponding asynchronous spectrum develops at least two peaks, even for a small shift coupled with an appreciable intensity variation. The separation between these peaks increases upon an increase in the bandwidth. If the spectral data are changing monotonically, the number and positions of the synchronous features can be readily determined from the difference between the first and the last spectrum in the series. The correlation spectrum calculated without the subtraction of reference spectrum, for a single band that shifts with constant intensity, is similar to that calculated without the subtraction of reference, for a band undergoing shift combined with significant intensity variations. The synchronous peaks resulting from the exponentially decaying intensity changes alone are at least 10 times more intense than the corresponding asynchronous peaks, whereas the analogous intensity ratio due to a moderate band shift is discernibly lower. This result proves that the asynchronous spectra are more sensitive to the band shift than the synchronous spectra. Also, the effect of noise is more apparent in the case of the asynchronous spectrum. The bandwidth variation alone generates noticeably weaker correlation intensity than that due to the band position or intensity changes. It has been shown that the asynchronous intensity strongly depends on the overall extent of the intensity changes at particular wavenumbers. As a result, the bands changing their intensities extensively but at similar rates may develop more intense asynchronicity than the bands with distinct difference in the rates of the intensity changes but smaller magnitude of these changes.
Nonlinear Two-Dimensional Vibrational Spectroscopy
Authors: Zhao Wei , Murdoch Keith M. , Besemann Daniel M. , Condon Nicholas J. , Meyer Kent A. , Wright John C.
Published: October 2003

There is currently great interest in developing the vibrational analog to two-dimensional NMR spectroscopy. One approach to implementing two-dimensional vibrational spectroscopy is to use doubly vibrationally enhanced (DOVE) four-wave mixing (FWM). Nonlinear signals occur because of correlations and mode coupling that are induced by interactions involving the driven modes. Since cross peaks do not occur between modes if interactions are absent, spectral congestion is removed and only the coupled modes remain. We describe the development of a two-dimensional doubly vibrationally enhanced four wave mixing method that extends the doubly resonant nonlinear spectroscopies to vibrational nonlinearities. We demonstrate the selective enhancements of coupled modes that are possible with the double resonances where the intensity of the enhancements reflects the strength of the interactions that are responsible for the vibrational mode coupling. We also demonstrate the capabilities for selectively enhancing specific sample components in an isotopic mixture. Since biological applications of DOVE require aqueous environments, we have examined the ability of DOVE methods to discriminate against the strong water absorption and have found that water has a small vibrational nonlinearity that allows DOVE of the solutes. Our results demonstrate the feasibility and features required to make DOVE methods practical for a wide range of scientific applications where identification of intra- and intermolecular interactions is important.
Flow Analysis-Based Surface-Enhanced Raman Spectroscopy Employing Exchangeable Microbeads as SERS-Active Surfaces
Authors: Lendl Bernhard , Ehmoser Horst , Frank Johannes , Schindler Rupert
Published: October 2003

This paper reports on a new fully automated approach for highly sensitive and robust surface-enhanced Raman spectroscopic (SERS) detection using flow systems. An aqueous solution of silver nitrate was reduced by the addition of sodium borohydride and the thus formed silver sols adsorbed on Sephadex anion exchanger microbeads (dry bead size: 50–120 μm) present in the reaction mixture. In this way microbeads carrying a SERS-active layer were generated that could be easily pumped in the flow system without facing problems due to Ag-sol adsorption on the Teflon® tubing. After online generation of the SERS-active microbeads, the analyte (test analyte: nicotinic acid) was added, and the homogeneous SERS–microbead–analyte suspension pumped into a specially designed flow cell where the beads were retained and the SERS spectra measured with a Fourier transform (FT)-Raman instrument with a laser wavelength of 1064 nm. Afterwards the SERS microbeads were discarded by flow reversal and new, freshly prepared SERS microbeads together with the analyte could be introduced automatically into the flow system. The developed method is characterized by complete computer control of all operation steps, high sensitivity of the SERS measurement, high precision, and long-term stability. The concentration dependence of the SERS signals was investigated over a range from 5·10−6 M to 0.1 M nicotinic acid. The signal intensities increased until 1 mM, after which no further rise in the SERS intensities was found. Typical precision achieved was 8% throughout the whole calibration range.
Angle-Resolved Laser-Induced Breakdown Spectrometry for Depth Profiling of Coated Materials
Authors: García C. C. , Corral M. , Vadillo J. M. , Laserna J. J.
Published: October 2003

The combination of angle-resolved laser ablation with the use of a collimated beam is presented as a new approach to increase the depth-resolved capabilities of laser-induced breakdown spectrometry (LIBS). The effect of beam conditioning and the reduction of the effective sampling depth due to the angular dependence of laser ablation allow ablation rates lower than 2 nm/pulse for coated materials (Sn-coated steels and Cr-coated samples). Spectral information is obtained on a single-laser-shot basis. The effect of incidence angle has been examined from differentiated emission profiles, demonstrating the beneficial effect of working at incidence different from normal. A compromise between depth resolution and emission signal must be found at large angles due to the lower irradiance resulting from the increase in beam size at the interface for large angles of incidence. A comparison of the proposed approach with the analysis provided by a commercial glow-discharge device [glow discharge optical emission spectroscopy (GD-OES)] demonstrated quite satisfactory results.
Spark Ablation Inductively Coupled Plasma Mass Spectrometry Applied to the Semi-Quantitative Panoramic Analysis of Ferroalloys
Authors: Coedo A. G. , Dorado T. , Padilla I. , Fernandez B. J.
Published: October 2003

The coupling of inductively coupled plasma mass spectrometry (ICP-MS) with spark ablation (SA) was applied for the semi-quantitative determination of impurities in different types of ferroalloys. The sparking operating conditions were optimized, and a restrictive path including a cyclone and a spray chamber was used to decrease the quantity of sparked material reaching the plasma, to prevent torch injector and sampling cone blockage. Samples were mixed in a 1:2 sample-to-graphite ratio and pressed into pellets for direct solid sampling by the spark. The advantage of the technique includes the benefit of easily determining some refractory elements that are very difficult to dissolve. The method was tested on three different types of ferroalloys: Fe-Ti, Fe-Nb, and Fe-V. A single standard ferroalloy sample was used as an external calibration sample to create a complete response curve for each type of ferroalloy base. Industrial ferroalloys, chemically characterized by using different analytical methods, were applied as calibration samples. The use of a calibration sample closely matching the ferroalloy material to be analyzed was found to be essential if accurate analyses were to be obtained. Certified Reference Materials of the three ferroalloys types tested—BAS (Bureau of Analyzed Samples) 579-1 (Fe-Nb alloy); BAM (Bundesanstalt für Materialprüfung) 589-1 (Fe-Ti alloy); and BAS 577-1 (Fe-V alloy)—were analyzed to evaluate the accuracy attainable in this panoramic mode. Most of the results, ranging from 0.05% to 5% m/m, were observed to be accurate to within 6–18.6% of the certified value, and the precision was better than 17.8% relative standard deviation. Determination limits based on 10 times the standard deviation of six replicates of a blank graphite pellet were on the μg g−1 level.
Evaluation of a Microconcentric Nebulizer and its Suction Effect in a Capillary Electrophoresis Interface with Inductively Coupled Plasma Mass Spectrometry
Authors: B'Hymer Clayton , Day Jason A. , Caruso Joseph A.
Published: October 2003

An experimental consideration and common difficulty when interfacing capillary electrophoresis (CE) with plasma mass spectrometry via a pneumatic nebulizer is the suction effect caused by the natural aspiration of the nebulizer. This is a significant effect in terms of the CE experiment, since it can seriously degrade the separation of analytes. In this study, a pneumatic microconcentric nebulizer was studied as a CE interface with inductively coupled plasma mass spectrometry (ICP-MS). A self-aspirating sheath flow interface technique was used to reduce the suction effect of the nebulizer by using a separation of metallothionein I and ferritin. However, the sheath flow or make-up buffer technique has not been studied sufficiently with respect to all the effects on the CE analysis. In this evaluation, a sol-gel frit was placed in the sample introduction end in this CE system, and the contribution of the suction effect to both sample response from sample loading and elution times was observed. It was found that the studied microconcentric nebulizer could be used effectively with the self-aspirating sheath flow technique; however, the contribution of the suction effect to sample loading to the CE system is very high. The peak area response difference of an open capillary vs. a sol-gel fritted capillary was approximately one order of magnitude greater. Also, the fritted capillary experiments showed that the contribution to migration time from aspiration of the nebulizer through the CE capillary is very significant.
Two-Dimensional Infrared Correlation Analysis of Protein Unfolding: Use of Spectral Simulations to Validate Structural Changes during Thermal Denaturation of Bacterial CMP Kinases
Authors: Schultz Christian P. , Bârzu Octavian , Mantsch Henry H.
Published: October 2003

The functional role of bacterial CMP kinases is to recover the energetically exhausted nucleoside monophosphates derived from cell metabolism by transferring a phosphate residue from ATP to CMP or dCMP. These enzymes—important for cell growth and division—possess two distinct binding sites and a number of conserved secondary structure elements. Herein we compare the infrared spectra of two similar, but not identical, CMP kinases from Escherichia coli and Bacillus subtilis. The two-dimensional correlation analysis of the infrared spectra of the two enzymes reveals significant differences in protein structure upon denaturation, a fact possibly linked to their different biochemical and catalytic properties. Model calculations are used to illustrate the effect of two separate processes on the out-of-phase correlation in the two-dimensional (2D) correlation plots. This strategy is then employed to validate the changes observed in the secondary structure of the two enzymes. When bound to the active site of the protein, the two substrates CMP and ATP exert a stabilizing effect on the structure of both proteins; however, the changes observed upon thermal denaturation are different for the two enzymes. Model 2D correlations that simulate the denaturation of the two enzymes confirm the occurrence of temperature-delayed unfolding processes in both proteins. Thermal denaturation and aggregation can be distinguished in both proteins as two distinct processes, separated in time.
NMR Spectra of Cyclic Formals Formed during the Early Stage of the Copolymerization of Trioxane and Ethylene Oxide
Authors: Yamasaki Naoaki , Masamoto Junzo , Kanaori Kenji
Published: October 2003

During the early stage of the copolymerization of trioxane and ethylene oxide, we found the formation of three novel cyclic compounds: 1,3,5,7-tetraoxacyclononane (TOCN), 1,3,5,7,10-pentaoxacyclododecane (POCD), and 1,3,5,7,10,13-hexaoxacyclopentadecane (HOCP). These novel cyclic compounds were new direct reaction products of 1 mole of trioxane and 1 mole of ethylene oxide, 1 mole of trioxane and 2 moles of ethylene oxide, and 1 mole of trioxane and 3 moles of ethylene oxide, respectively. We compared the 1H-NMR and 13C-NMR spectra of each cyclic compound and precisely assigned the signals of each spectrum using NOESY (nuclear Overhauser enhancement spectroscopy) and HETCOR (heteronuclear correlated spectroscopy). We also compared the 1H-NMR spectra of POCD and HOCP with the corresponding cyclic formals with one oxymethylene unit, diethylene glycol formal (DEGF) and triethylene glycol formal (TEGF). Interestingly, we found that DEGF and TEGF, which have only one oxymethylene unit, showed no proton splitting of the oxyethylene units, while POCD and HOCP, which have three consecutive oxymethylene units, have split signals for the oxyethylene units.