bluuebunny/crossref_metadata_2025 huggingface dataset:
Consistency in Circle Cell FT-IR Analysis of Aqueous Solutions
Authors: Braue Ernest H. , Pannella Michael G.
Published: July 2005

The CIRCLE CELL®, based on the cylindrical internal reflection technique (CIR), has become a popular FT-IR accessory because it allows for easy collection of IR spectra from aqueous solutions. In this paper we describe a detailed study of the quality of quantification possible with the use of aqueous acetone mixtures over a concentration range of 0.01 to 90% (w/w). During a period of four months, the method's sensitivity, accuracy, precision, and time stability were evaluated. With the use of a Nicolet 60SX FT-IR, an MCT-A detector, 500 scans, and a 300-s sampling delay, five sets of triplicate runs, approximately one month apart, were made at each of 10 concentrations. Our results indicate the following conclusions: (1) quantification by peak height gives better precision, whereas peak area gives a more linear response and correlation with Beer's law over a large concentration range; (2) water bands produce spectral artifacts during subtraction, (3) repositioning of the CIRCLE CELL® optical bench between runs and the micro-boat sampling cell between samples critically affects the quantification results; (4) deviations from Beer's law are caused by chemical effects and insufficient resolution errors; and (5) the reliable sensitivity limit is 0.05% w/w. These findings suggest that precise quantitative analysis of aqueous solutions is now a practical method with the use of FT-IR spectroscopy.
Direct Introduction of Aqueous Samples into a Low-Powered Microwave-Induced Plasma for Atomic Emission Spectrometry
Authors: Long Gary L. , Perkins Larry D.
Published: July 2005

The direct introduction of aqueous samples into a low-power microwave plasma is achieved with the use of a highly efficient TM010 microwave plasma. A toroidal plasma is sustained in the cavity solely by the Ar gas output of the nebulizer. Samples from a concentric glass nebulizer/Scott type spray chamber are fed directly into the cavity with no desolvation apparatus. A toroidal plasma can be sustained from the output of the nebulizer while 1 mL/min water is being aspirated at power levels of 36 W. This plasma is characterized as an atom cell by the study of emission profiles, working curves, and limits of detection. Also, ionization and vaporization interferences that occur with the use of this plasma are discussed.
The Influence of Selected Metals on the Aromatic System of Salicylic Acid
Authors: Lewandowski Włodzimierz , Baranska Halina
Published: July 2005

Results are presented of research on the influence of Na, Mg, Cd, Al, La(III), Pb(II), Hg(I), and Hg(II) on the aromatic system of salicylic acid. Salicylic acid is regarded here as a model compound representing a wide group of aromatic ligands which are components of enzymes. The number, frequency, and relative intensities of bands in the vibrational (Raman and IR) spectra and the frequencies of the π → π* bands in the electronic (UV) spectra were analyzed. The analysis showed that metal-aromatic ligand complex formation causes significant changes in the frequencies and relative intensities of the bands associated with the aromatic system in the following regions: 1640–1370, 1350–1300, 1200–1090, and 800–650 cm−1. It was concluded that Na, Hg(I and II), Pb(II), and Cd perturb the aromatic system of salicylic acid, whereas La(III) and Al stabilize it.
A Unified Analysis of Noncomparative Methods for Measuring the Molar Absorptivity of Triplet-Triplet Transitions
Authors: Carmichael Ian , Hug G. L.
Published: July 2005

Noncomparative techniques for the measurement of the molar absorptivity of triplet-triplet absorption transitions, εT*, are reviewed. The methods covered include singlet depletion, total depletion, intensity variation (and its pulsed analog), partial saturation, and the so-called kinetic method. A critical analysis of the conceptual foundations of these varied approaches is performed. The fundamental equations of each technique are derived from a general three-state kinetic model of excitation and decay. From this unified approach it becomes very clear where assumptions are made in the traditional derivations of the methods. Additionally, one comparative method, that termed relative actinometry, is discussed, since it may be treated in a unimolecular fashion consistent with the above approach. The only major εT* method excluded from this review is that involving intermolecular energy transfer, a technique which has been thoroughly documented elsewhere.
The Temperature Dependence of Band Maxima Molar Absorptivities of the Carbon-Bromine Stretching Modes in n-Butyl Bromide in the Liquid Phase
Authors: Katon J. E. , Lobo Stanislaus R. , Simpson J. C.
Published: July 2005

In the determination of energy differences of conformers in the fluid states by infrared spectroscopy it is nearly always assumed that the ratio of the molar absorptivities at the band maxima of two separate absorption bands is independent of temperature. This assumption has been tested by fitting the data obtained from n-butyl bromide to a mathematical model which can be iterated to convergence on a value of the energy difference between the trans and gauche isomers. The data utilized are the C-Br stretching modes of the two conformers at about 655 and 567 cm−1, respectively. It is shown that the assumption of temperature independence of the ratios of the molar absorptivities at the peak maxima is a good one, although both values are individually temperature dependent.
Fourier Transform Raman Spectroscopy of Long-Chain Molecules Containing Strongly Absorbing Chromophores
Authors: Zimba C. G. , Hallmark V. M. , Swalen J. D. , Rabolt J. F.
Published: July 2005

Fourier transform Raman spectroscopy shows considerable promise as a new characterization technique for molecules which contain chromophores which absorb in the visible region, the region where conventional Raman measurements are made. With the use of near-infrared excitation, spectra in the absence of fluorescence and resonance enhancement are obtained. These advantages can be further enhanced if the collection of data using this technique becomes routine, requiring a level of complexity comparable to that of conventional Raman scattering. Toward that end, the implementation of a 90° scattering geometry in our FT-Raman measurements was undertaken, and the results are shown to be at least comparable to those obtained with the use of reflective optics in a 180° geometry. A number of results on both liquids and solids have also been obtained in order to compare FT-Raman with conventional scanning Raman measurements.
Determination of Trace Elements in Trimethylaluminum by Inductively Coupled Plasma-Atomic Emission Spectrometry
Authors: Murty Pappu S. , Barnes Ramon M.
Published: July 2005

A method was developed for the analysis of trimethylaluminum (TMA) by inductively coupled plasma-atomic emission spectrometry (ICP-AES). TMA was decomposed with 95% ethanol, and the aqueous solution of the decomposition product was used for the determination of six trace elements (Cu, Fe, Ga, Mg, Si, and Zn). Aluminum also was determined after dilution of the aqueous solution. The reproducibility of the overall decomposition and measurement procedures was <15%. Except for gallium, the limits of detection were <0.5 μg/g of TMA.
Ionization Temperatures in the Inductively Coupled Plasma Determined by Mass Spectrometry
Authors: Wilson Daniel A. , Vickers George H. , Hieftje Gary M.
Published: July 2005

Ionization temperatures in the inductively coupled plasma are determined with the use of the ionization fraction for iodine obtained by mass-spectral sampling. Temperatures profiled at different heights and different positions across the plasma are between 6900 and 7800 K at relatively low heights. Power increases raise the measured ionization temperature, while changes in nebulizer gas flow and the addition of an easily ionized element to the plasma have no measurable effect. Desolvation of the sample aerosol causes a decrease of about 500 K in the ionization temperature.
A Standard Session Stopped-Flow NMR Tube
Authors: Green David B. , Lane James , Wing Richard M.
Published: July 2005

An NMR tube has been designed to allow stopped-flow NMR experiments to be done with no modification of the instrument. Thus this technique is made routine for organic and inorganic chemists. The tube can be used with any iron magnet or super-conducting system, but the technique requires a Fourier transform data collection capability. The tube is easily attached to standard stopped-flow supply and stopping syringes, making routine data collection possible at a 0.6 s/spectra sampling rate. A calibration procedure and a sample chemical kinetic study are included to demonstrate the use of the tube.
Vibrational Spectroscopy of Iodine-Doped Substituted Polyacetylenes
Authors: Ferraro John R. , Furlani Anita , Russo Maria Vittoria
Published: July 2005

Raman and far-infrared (FIR) data for iodine-doped substituted polyacetylenes, such as poly(2-propyn-1-ol)-(POHP) and poly(benzylpropargylamine)-(PBPA) are reported. The data are consistent with an I5−(I2 … I3)− dopant species in the heavily doped polymers. Solution and solid data provided similar vibrational results. Stability of the polymeric radical cation and the polyiodide anion moiety in tetrahydrofuran is attributed to the solvation effects of the ions by the solvent. New data on heavily doped poly(phenyl)acetylene (PPA) are presented.
Electron Number Density Studies in Moderate-Power Argon and Helium Microwave-Induced Plasmas
Authors: Brown Peter G. , Brotherton Timothy J. , Workman John M. , Caruso Joseph A.
Published: July 2005

The electron number density of atmospheric-pressure argon and helium microwave-induced plasmas operating in the power regime of 100 to 450 W has been examined. The resulting data demonstrate a trend of increasing electron density, ne, for both the Ar and He microwave-induced plasmas as forward power is increased. An examination of ne vs. plasma observation position demonstrates a maximum in ne at the central plasma observation position for both plasmas. Further, spatial dependence of electron density appears to be more pronounced at high power levels. Nebulization of aqueous solutions containing varying concentrations of an easily ionizable element into the Ar microwave-induced plasma, MIP, demonstrates little if any effect on ne. Moreover, this observation can be explained by the fact that there is a far greater quantity of water than easily ionizable element being introduced into the plasma in a given time period. Thus the electron contribution resulting from water degradation products in the plasma far outweighs that from the relatively small amount of easily ionizable element present. This last point is further substantiated by an examination of the Ar MIP with and without solution nebulization.
Influence of Instrument Parameters on Nonspectroscopic Interferences in Inductively Coupled Plasma-Mass Spectrometry
Authors: Gregoire D. C.
Published: July 2005

The effect of ion lens voltage settings and plasma conditions on nonspectroscopic interferences has been studied. The change in ion count rate for 7Li, 10B, 45Sc, and 89Y in the presence of Na, K, Sr, and Cs under a variety of experimental conditions is reported. The ion lens voltage setting did not affect the degree of nonspectroscopic interferences with the use of the Einzel ion optic system. Suppression effects were increased when the power was increased and the sampling depth decreased. Changes in nebulizer pressure resulted in interference trends, which varied with the concomitant element being studied. Sodium caused a decrease in interference effects with increasing nebulizer pressure, whereas Cs caused an increase under the same experimental conditions. Suppression of analyte ion count rate increased with increasing sample solution uptake rate and increasing atomic mass of concomitant elements.
Electrochemical Preconcentration of Trace Metals for Simultaneous Multielement Determination by Inductively Coupled Plasma-Atomic Emission Spectrometry Utilizing Graphite-Cup Direct-Insertion Technique
Authors: Abdullah Mohammad , Fuwa Keiichiro , Haraguchi Hiroki
Published: July 2005

Electrochemical preconcentration of trace metals on a graphite cup for multielement determination by inductively coupled plasma-atomic emission spectrometry (ICP-AES) is described, where controlled potential electrolysis of trace metals in an electrolyte solution similar to seawater has been examined by the use of a newly designed Teflon® cell to allow cathodic deposition. The characteristic of the present system is to make deposition of trace metals only inside a graphite cup, which is inserted into the plasma for the analysis by ICP-AES with the use of a computer-controlled graphite-cup direct-insertion technique. The electrolysis parameters and the solution circulation rates during electrolysis and washing of deposit have been optimized by a univariate search method. With the present experimental system, it is possible to preconcentrate trace metals by a factor of 30 to 300, and to separate them from the major matrix consituents, such as NaCl, KCl, and MgCl2, in artificial seawater. The detection limits for Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn at the pg/mL level can be obtained with relative standard deviation of 2 to 11%.
A Study of Internal Standardization in Inductively Coupled Plasma-Mass Spectrometry
Authors: Thompson Joseph J. , Houk R. S.
Published: July 2005

Internal standardization is employed to compensate for ionization suppression in inductively coupled plasma-mass spectrometry (ICP-MS). By examination of the response of over 50 elements to a sodium matrix under different operating conditions, it is apparent that an internal standard is most effective when it is close in mass and ionization energy to the analyte. The extent of suppression and the relative order of suppression of various analyte elements can differ for various matrix elements. Generally, precision was improved by the use of internal standardization; the extent of improvement differed for different analyte elements and operating conditions. A comparison between ICP-MS with ultrasonic and pneumatic nebulization is described. The ultrasonic nebulizer usually exhibits better sensitivity and detection limits for analyte elements, unless the extent of suppression induced by the concomitant matrix is very high.
Remote Sensing Fiber Optic Probe NIR Spectroscopy Coupled with Chemometric Data Treatment
Authors: Weyer L. G. , Becker K. J. , Leach H. B.
Published: July 2005

A near-infrared fiber optic probe remote sensing spectroscopic system has been developed for online multicomponent composition analysis. The Guided Wave Model 200 UV-VIS-NIR spectrophotometer has been evaluated as the base of this system. Multiple linear regression (MLR) software has been combined with data transfer, graphics, and online monitoring programs. The system has been evaluated in plant trials to monitor the composition of mixed alcohol purification streams, mixed solvent distillate, and a fatty acid derivative. The combined use of derivative spectroscopy and MLR data treatment provided good prediction equations for the real-time (20 s) monitoring of the concentrations of several components in moving streams.
Determination of Species Sampled by an Analytical Spark Discharge Using Time- and Spatially Resolved (Anomalous Dispersion) “Hook” Spectroscopy
Authors: Hsu Wu-Hwa , Majidi Vahid , Coleman David M.
Published: July 2005

We report the first application of time- and spatially resolved “hook” spectroscopy to quantitatively determine the number density of species sampled by an atmospheric-pressure analytical spark discharge. The new instrument consists of a tunable dye laser light source, a Mach-Zehnder interferometer, a stigmatic spectrograph, and a high-fidelity image transfer system. The integrated number densities of ground-state sodium atoms, ablated from a graphite electrode containing NaCl, are deduced from the corrresponding hook spectrum. Data are obtained at different spatial windows with respect to the interelectrode axis and also at different times after the spark breakdown. Advantages and limitations of the approach are discussed.
Near-Surface Analysis and Depth Profiling by FT-IR Photoacoustic Spectroscopy
Authors: Yang Charles Q. , Bresee Randall R. , Fateley William G.
Published: July 2005

Fourier transform photoacoustic spectroscopy (FT-IR/PAS) has proven to be a powerful technique for the near-surface characterization of solid materials. The effective sampling depth of FT-IR/PAS can be varied by using different interferometer mirror velocities, so that nondestructive depth profiling can be performed. In this research, sized cotton yarns, treated glass fibers, chemically modified poly(ethylene terephthalate) fibers, and a naturally weathered poly(vinyl chloride) composite were investigated with the use of FT-IR/PAS at different mirror velocities. Penetration of the chemical additives in these materials was studied. It was demonstrated that FT-IR/PAS has the ability to investigate the changes in chemical nature within the detectable surface layers of solid samples.
Effect of Easily Ionized Elements upon the Spatial Emission Properties of Microwave-Induced Plasmas
Authors: Selby Mark , Rezaaiyaan Ruhangiz , Hieftje Gary M.
Published: July 2005

Spatially resolved measurements of emission from microwave-induced plasmas (MIPs) sustained in helium in a Beenakker resonant cavity and in a surfatron have been compared and contrasted. Particular emphasis has been placed upon the study of a common interference effect in MIP sources, namely the enhancement (or suppression in some instances) of analyte emission intensity by matrices containing an easily ionized element (EIE). The presence of the EIE caused a strong enhancement of analyte emission in the Beenakker cavity system but had a relatively smaller influence upon analyte emission in the surfatron system at higher concentrations of EIE. The difference in behavior between the two systems toward EIEs appears to be attributable to improved sample injection into the plasma in the case of the surfatron.
Examination of the Matrix Isolation Fourier Transform Infrared Spectra of Organic Compounds, Part I
Authors: Coleman W. M. , Gordon Bert M.
Published: July 2005

Data are presented that describe the IR spectra of organic compounds obtained under matrix isolation conditions. Among the types of compounds examined are amides, lactones, lactams, esters, acids, alcohols, and phenols. Trends, as a function of structure, established in vapor-phase IR are shown to exist under MI conditions. The frequency (cm−1) of the stretching absorption for hydroxyl groups and carbonyl groups associated with the types of compounds listed above under MI conditions is shown to be intermediate between the vapor-phase position (highest energy) and the solid-solution position (lowest energy). In some cases the three phases differ by as much as 300 cm−1 (OH group in carboxylic acids) and by as little as 15 cm−1 (carbonyl group in carboxylic acid esters).
Spatial Emission Properties of a Surface-Wave-Sustained Plasma (Surfatron) in Helium
Authors: Selby Mark , Rezaaiyaan Ruhangiz , Hieftje Gary M.
Published: July 2005

Spatially resolved measurements of plasma-emission sources can greatly aid in their application to atomic-emission spectrometry. In this study, detailed two-dimensional emission profiles of a plasma sustained by electromagnetic surface waves from a surfatron have been measured with an imaging spectrometer. In helium, and under the operating conditions described, the plasma is found to possess a “doughnut” shape much like the inductively coupled plasma (ICP) in argon. Emission from the following types of spectral features was found to be confined to the plasma annulus: (1) He(I) lines; (2) molecular bands; (3) background continuum; (4) difficult-to-excite transitions from nonmetallic analytes. In contrast, two-dimensional profiles for metallic analytes (introduced in the form of an aerosol from a glass-frit nebulizer) show localized maxima along the central axis of the plasma. Spatially resolved measurements have suggested ways in which the surfatron can be employed to advantage for atomic emission spectrometry. Possible excitation mechanisms to account for the spatial properties of the surfatron are also offered.
Magnetically Tailored Arc and Glow Discharge Plasmas for Atomic Spectroscopy
Authors: Trivedi K. , Tanguay S. , Matties M. , Sacks R.
Published: July 2005

Three magnetic field-plasma configurations are used to study the interaction of external magnetic fields with analytically useful plasma devices. First, a magnetic field oscillating at 60 Hz and normal to the electric field in a 12-A direct current arc plasma is used to obtain an Ē×B̄ drift motion of the arc current channel. This causes a periodic vertical displacement of the channel. Second, a cw magnetic field is used to alter the structure and radiative properties of a demountable glow discharge lamp that uses a center-post cathode. The magnetic field axis is parallel to the cathode axis, and the lamp is operated in a pseudo-magnetron mode. Third, a damped, oscillatory magnetic field produced by discharging a capacitor through a coil is used to alter the radiative characteristics of several commercial hollow cathode lamps. The magnetic field is parallel to the cathode axis, and again the lamps operate in a pseudo-magnetron mode. In all three systems, the presence of the magnetic field drastically alters the radiative properties of the plasmas.
Tetrachlorodibenzo-p-Dioxin Isomer Differentiation by Capillary Gas Chromatography Fourier Transform-Infrared Spectroscopy
Authors: Grainger James , Gelbaum Leslie T.
Published: July 2005

Reference infrared vapor-phase spectra of the 22 tetrachlorodibenzo-dioxin (TCDD) isomers were recorded at low microgram concentrations. These reference spectra of synthetic mixture components separated chromatographically or by spectral subtraction exhibit distinct infrared spectra for each isomer. The infrared frequencies are delineated in correlation tables and are interpreted in terms of substitution patterns which determine the strength of the ether linkage. Absorbance values in the 1330–1280 cm−1 (C-O-C asymmetric stretch) region correlate with specific substitution patterns and molecular geometry. Relative electron-withdrawing capacities for chlorinated aromatic rings in TCDD isomers were estimated on the basis of relative capacities determined for model compounds. Qualitative correlations were established between electron-withdrawing capacities and the effects of resonance and field interactions on the ether linkage absorption frequencies of individual TCDD isomers. Gas chromatography Fourier transform infrared (GC/FT-IR) isomer assignments are generally consistent with those obtained by proton Fourier transform nuclear magnetic resonance (1H FT/NMR) and flame ionization gas chromatography (GC/FID). A chromatographically independent method of assigning TCDD isomer structures on the basis of ether linkage asymmetric stretching frequencies was established by utilization of valence-bond approximations. GC/FT-IR assignments for several TCDD isomers differ from isomer assignments in previously published results. A user-generated, vapor-phase reference library, containing individual TCDD spectra and spectra of isomer pairs that are incompletely resolved on chromatographic columns, correctly identified each isomer in variety of mixtures by means of a software algorithm.
Structure of Styrene/Acrylic Acid Copolymer in Aqueous Solution Determined by Fourier Transform Infrared Spectroscopy
Authors: Urban Marek W. , Koenig Jack L. , Shih L. B. , Allaway James R.
Published: July 2005

A random styrene/acrylic acid copolymer has been examined by Fourier transform infrared spectroscopy with the use of the attenuated total reflectance (ATR) technique, in a study of the conformational structure in aqueous solution. The presence of a base in the aqueous solution leads to ionization of the acrylic acid segments and to conformational changes. The ionization is demonstrated by the appearance of asymmetric and symmetric C-O stretching bands of the COO− ion at 1547 and 1407 cm−1. Our results show that the water molecules are coordinated to the COO− ion through the positively charged cations. The acrylic segments of the copolymer are exposed to the aqueous solvent, whereas styrene is surrounded by acrylates. The molecular interactions of the copolymer in the two-phase water and benzyl alcohol system are determined. In the benzyl alcohol phase, the copolymer forms a coil-type structure, with the acrylic acid segments exposed to the aqueous phase. With time, the cations diffuse into the benzyl alcohol phase and cause ionization of the acrylic acid units, resulting in formation of the COO− ions.
Relation of the Acute Pulmonary Response to Cotton Dust and Dust Compositional Analysis by Near-Infrared Reflectance Spectroscopy. Part I: Elutriated Dust
Authors: Montalvo Joseph G. , Faught Sherman E. , Buco Steven M. , Saxton Arnold M.
Published: July 2005

The near-infrared reflectance spectroscopy (NIRS) method of analysis, as applied to cotton dust, offers an independent method for searching for byssinosis causatives. We wish to report here a test of the hypothesis that the acute pulmonary response from subjects exposed to cotton dust is a linear function of the composition of elutriated dust as measured by near-infrared reflectance spectroscopy (NIRS). Indeed, a linear relationship was found between delta FEV1 (the forced expiratory volume in one second) and cotton dust captured by the vertical elutriator cotton dust sampler. Of the various agents proposed over the years as the byssinosis causative agent, at least three of them (gram-negative bacteria and their endotoxin, and tannins) were present in the dust at concentrations exceeding the NIRS sensitivity level, and may account for the observed relationship.
An Infrared Accessory for Studying the Emissivity of Aluminum Surfaces
Authors: Conroy C. M. , Guthrie J. D. , Sharkins A. J. , Sparr B. J. , Crocombe R. A. , Curbelo R.
Published: July 2005

Temperature measurement of aluminum surfaces by remote sensing of infrared radiation is difficult because of the low and varying emissivity of aluminum. The variation in emissivity may be dependent on factors like surface roughness, surface oxides, temperature, or wavelength of the measurement. In order that the factors which affect the emissivity of pure aluminum might be studied, a specialized emission accessory was built to be used in conjunction with a Fourier transform infrared spectrometer. This paper describes the design of the accessory and presents emission spectra and emissivity curves demonstrating the accessory's capabilities.
Laser Photolytic Fragmentation-Fluorescence Spectrometric Determination of Nitromethane
Authors: Schendel J. , Hohmann R. , Wehry E. L.
Published: July 2005

An experimental system has been developed wherein a pulsed laser beam photofragments molecules of a gaseous sample introduced into a vacuum chamber. Fluorescence of the fragments so produced is observed. Studies of emission by photoproducts of the excimer laser photolysis of nitromethane at 193 nm are reported here. The principal fragment emission occurs at 431 nm, due to the CH A2Δ-X2II transition. A limit of detection for nitromethane of 1.6 × 108 molecules is reported, corresponding to an interrogated sample volume of 0.0375 cm3 and a chamber pressure of 1.3 × 10−7 Torr (i.e., a concentration of 4.2 × 109 molecules/cm3). The linear dynamic range extends over 3.5 decades in nitromethane pressure. The fragment fluorescence measurements can be made with excellent precision (relative standard deviation of less than 4%). The CH fragment fluorescence signal is linear in the first power of laser fluence over the range of 60 to 135 mJ/pulse (0.8–1.8 J/cm2).
Optogalvanic Measurement of the Cathode-Fall Region of Kr Hollow Cathode Discharge
Authors: Fujimaki Shigehiko , Adachi Yukio , Hirose Chiaki
Published: July 2005

Optogalvanic observation of the Stark shift of the Kr 8d[3/2]20-5p[3/2]2 atomic line has been carried out on a Kr hollow cathode discharge in a discharge tube with a cylindrical cathode, at a fill pressure of 1 to 6 Torr (1 Torr = 133.322 Pa), and a discharge current from 1 to 10 mA, to reveal the linear decrease of electric field with radial distance from the cathode surface. Values of current density, charge density, and other discharge parameters have been derived and their behavior has been compared with theoretical formula; it is concluded that a major role is played by the photons from the negative-glow region. Unusual features observed in the discharge at 1 Torr pressure and above 5 mA of current have been attributed to the effect of Penning ionization of sputtered copper atoms.
Thermally Induced Raman Difference Spectroscopy
Authors: Savoie Rodrigue , Langlais Marc , Beauchesne Pierre
Published: July 2005

A dual illuminator suitable for Raman difference spectroscopy is described. The system, which can be readily adapted for use with computer-controlled Raman spectrometers, provides a differential frequency accuracy (ca. ±0.03 cm−1) which is comparable to that of other existing devices. The individual control of the temperature of each sample makes it possible to obtain thermally induced Raman difference spectra, where-by very small frequency shifts associated with changes in temperature can be accurately measured. An example of application to the study of the gel-to-liquid crystal transition of a phospholipid (DPPG) is given.
Sample Cells for Studies of Catalytic Materials by ESR and NMR Spectroscopies
Authors: Mesaros D. V. , Dybowski Cecil
Published: July 2005

We describe the construction of sample cells for ESR and NMR spectroscopy of air-sensitive materials. The cells are designed for repeated exposure of the material to an atmosphere through attachment to a gas manifold, as would occur in studies of sorption onto heterogeneous catalysts and in flow systems.
A Helium Inductively Coupled Plasma: Background Spectra Emitted in the Red and Near-Infrared Spectral Regions
Authors: Chan Shi-Kit , Montaser Akbar
Published: July 2005

The atomic emission spectrum of a He ICP, generated in a low-gas-flow torch, was recorded for the wavelength range of 630 to 950 nm. In general, the background spectrum of the He ICP is much simpler than that of an Ar ICP. In contrast to the Ar ICP, prominent lines of Br, C, CI, I, and S in the He ICP are free from spectral interferences.
Gas Electron Diffraction Study of the 193-nm Laser-Induced Interconversion between Cis- and Trans-1,2-Dichloroethylene
Authors: Monts D. L. , Ewbank J. D. , Siam K. , Faust W. L. , Paul D. W. , Schäfer L.
Published: July 2005

Gas electron diffraction (GED) data were recorded of 193-nm irradiated cis- and trans-1,2-dichloroethylene. The interconversion between the cis-and trans-isomers and the formation of chloroacetylene can be inferred from the diffraction intensities. The experiments demonstrate the utility of GED in the study of chemical reactions.
A Novel Version of the Microwave-Coupled Hollow Cathode Lamp for Atomic Emission Spectrometry
Authors: Caroli S. , Senofonte O. , Violante N. , Simone L. Di
Published: July 2005

A new model of the microwave-boosted hollow cathode lamp has been devised, giving considerable improvement in the coupling efficiency of the two types of discharges. For this to be achieved, a resonant cavity is interposed between the cathodic and anodic blocks of the demountable tube, causing the microwave field to interact with the plasma inside the cathode. The performance of this potentiated lamp has been tested discharging a number of elements (Al, C, Cu, Fe, Mo and Ni). In all instances there was a significant increase in intensity of the emitted spectra, together with a noticeable diminution of background; thus signal-to-background ratios of even two orders of magnitude higher than those obtainable by conventional hollow cathode discharge lamps were achieved. An additional advantage of this combined lamp is its high stability of operation.
Infrared Spectroscopy of Surface Films and Powders Using a Metal Light Pipe (Theory)
Authors: Hansen Wilford N. , Hansen Galen J.
Published: July 2005

A theory is presented for metal light pipe spectroscopy in the infrared. Methods are described for producing sensitive spectra of thin films and powders inside the pipe. Propagation of infrared radiation down the pipe is analyzed. Sensitivities and resultant spectral shapes are predicted. There is a discussion about how to get optimum signal-to-noise ratios for instrument drift-limited spectra typical of FT-IR spectroscopy in the present application. Considered in the optical theory are the effects of skew rays, effects of light scattering, effects of pipe bending, and the presence of absorbing gasses. The method is predicted to be ideal for monolayer absorption spectroscopy.
Relative Ionization Yields for Impurity Elements in Laser Mass Spectrometry of Steels and Brasses
Authors: Huang L. Q. , Conzemius R. J. , Houk R. S.
Published: July 2005

Relative sensitivity factors (RSF) are studied for impurity elements in metal samples with the use of laser mass spectrometry in the power density range of 1 to 3 × 109 W cm−2 for the focused laser beam. Metallic impurities are found to have RSFs near unity, while nonmetallic impurities are less efficiently ionized relative to iron. The results indicate uniform sensitivities for all the elements may be expected as the power density reaches 5 × 10' 109 cm−2, in agreement with earlier studies.
Excitation of Fluorescent Emission from Solutions at the Surface of Polymer Thin-Film Waveguides: An Integrated Optics Technique for the Sensing of Fluorescence at the Polymer/Solution Interface
Authors: Reichert W. M. , Ives J. T. , Suci P. A. , Hlady V.
Published: July 2005

In this paper we report a technique for the excitation and collection of fluorescence in a flow cell coupled to the surface of an integrated optical waveguide. The waveguides were 1–2–µm-thick poly(styrene) films spuncast onto acid-cleaned Pyrex® microscope slides. The flow cell was used to introduce fluorescent solutions to the light energy at the polymer waveguide surface. The flow cell volume consisted of a 0.051-cm-thick silastic gasket sandwiched between a glass collection window and the polymer waveguide surface. Fluorescence data from the waveguide surface excitation of fluorescein solutions are presented. Evanescent- and scatter-excited emissions are separated with the use of light attenuation theory. The application of polymer thin-film waveguides to the study of protein adsorption at the polymer/solution interface is discussed.
Luminescence and Raman Spectroscopic Characterization of Tyrosine Oxidized by Persulfate
Authors: Cooper Thomas M. , Bolton David L. , Schuschereba Steven T. , Schmeisser Elmar T.
Published: July 2005

To gain insight into the photochemistry of oxidized amino acids, we have measured chemiluminescence and Raman spectra of persulfate oxidized tyrosine (POT). Chemiluminescence kinetics were obtained from a sealed capillary tube containing a basic POT solution. Excitation at 488.0 nm and monitoring emission at 633 nm produced a first-order rise and a second-order decay in intensity to steady-state levels. We collected steady-state emission spectra from a flow system excited by argon-ion and helium-neon laser radiation. The full-width at half-maximum, position, and intensity of fluorescence were measured. The full-width at half-maximum (3600 cm−1) was independent of excitation wavelength. At higher energy excitation, the emission maximum was independent of excitation line. At lower energy excitation, the emission maximum varied with the excitation line. The emission intensity dropped by a factor of 6 as the excitation wavelength was varied from 465.8 nm to 514.5 nm. Luminescence was also observed upon excitation at 632.8 nm of this compound dissolved in DMSO. Raman data, obtained from solid polymer suspended in a KBr pellet (rotating sample cell, 488.0 nm excitation, S cm−1 bandpass), revealed broad bands at 1385 cm−1, 1590–1615 cm−1, and 2930 cm−1 superimposed upon a weak fluorescent background. Upon ultraviolet laser excitation (363.8 nm, 5 mW power on the sample, 5 cm−1 bandpass), a single broad band appeared, centered at 1300 cm−1. The difference from visible excitation implies that resonance enhancement from an ultraviolet absorbing chromophore occurred.
A Comparison of Photothermal Deflection and Thermal Lensing Spectroscopy for Liquid Chromatographic Detection
Authors: Yang Yen , Ho Thanh Viet
Published: July 2005

A one-color pump/probe photothermal deflection detector for liquid chromatography is described and compared with its corresponding thermal lensing detection system. With 457.9-nm radiation from an argon-ion laser operated at a power level of 100 mW, both systems exhibit comparable detection limits. As a consequence, the choice between the two detectors is seemingly arbitrary. Other analytical aspects and potential for use are also compared and discussed.
Characterization of OH Radical 306.4 nm Emission in Argon and Helium Reduced-Pressure ICPs
Authors: Fleitz P. A. , Seliskar C. J.
Published: July 2005

The A → X emission of OH at 306.4 nm has been studied in reduced-pressure inductively coupled argon and helium plasmas. Under a variety of conditions of power and flow rate, a comparison of the A state rotational level distributions shows significant differences in the two plasmas. The rotational level distributions are generally nonlinear but can be quantitatively described as the sum of two separate Boltzmann distributions.
Raman Microprobe and Fourier Transform-Infrared Microsampling Studies of the Microstructure of Gallstones
Authors: Ishida H. , Kamoto R. , Uchida S. , Ishitani A. , Ozaki Y. , Iriyama K. , Tsukie E. , Shibata K. , Ishihara F. , Kameda H.
Published: July 2005

Several kinds of recently advanced microanalytical techniques—like electron probe x-ray microanalysis, laser Raman microprobe, and Fourier transform-infrared spectroscopy combined with a microsampling method—have been used for the study of the microstructure of gallstones. The organic and inorganic constituents of three kinds of gallstones are characterized on a microscopic scale. The microstructure of a cholesterol-bilirubin gallstone with a layered structure has been studied with particular emphasis. Small white particles contained in both a bilirubin gallstone and a cholesterol-bilirubin mixed gallstone have been found to consist of calcium salt of a fatty acid, probably calcium palmitate. The results obtained here will be very useful for understanding the mechanism of the gallstone-formation process.
The FT-IR Analysis by PAS and KBr Pellet of Cation-Exchanged Clay Mineral and Phosphonate Complexes
Authors: Rockley N. L. , Rockley M. G.
Published: July 2005

A comparison is made between the KBr pellet and FT-IR/PAS spectra of a series of interlamellar-cation-exchanged montmorillonites. Spectra of these clay minerals after adsorption of dimethyl methylphosphonate are also compared by the two spectroscopic methods. It is shown that the two infrared methods yield complementary spectral information, while FT-IR/PAS produces spectra with better definition of the adsorbate bands in all cases and superior reliability for observation of interlamellar ion-induced spectral shifts. Dimethyl methylphosphonate is shown to undergo interlamellar insertion, with bonding occurring directly through the P=0 moiety to the cation of the clay mineral. The strength of the bonding varies with the charge density of the cation.
The Structure of Hexane Soot. Part III: Ozonation Studies
Authors: Sergides C. A. , Jassim J. A. , Chughtai A. R. , Smith D. M.
Published: July 2005

The gravimetric estimation of CO2-evolved, FT-IR monitoring of the rate of formation of surface species, as well as several other measurements during the n-hexane soot/ozone reaction, has led to the conclusion that soot is a layered structure whose layers are chemically bonded, unlike the graphite structure where the layers are ordered by van der Waals forces. Fourier transform infrared spectroscopy, electrochemical analysis, microgravimetry, scanning electron microscopy (SEM), and the classical BET surface area determination technique have been employed in this work.
Extraction Discharge Source for Enhancing Analyte Line Intensities in Inductively Coupled Plasma Atomic Emission Spectrometry
Authors: Houk R. S. , Lafreniere B. R. , Lim H. B. , Fassel V. A.
Published: July 2005

A supplementary electrical discharge is generated by extraction of the axial channel of an Ar inductively coupled plasma (ICP) into a small vacuum chamber. The spectral background levels and background noise emitted by this discharge are similar to those from the ICP alone. The discharge enhances the intensities of ion lines by factors of up to 13 relative to intensities observed from the ICP alone. Neutral atom lines from elements with high ionization energies (≤9 eV) are also enhanced but by less than ion lines; neutral atom lines from easily ionized elements are suppressed by the discharge. Metal oxides in the ICP can be seen to dissociate into atomic species as they enter the discharge. These effects are attributed to more efficient atomization, excitation, and ionization in the discharge and to the tendency of analyte species to be constricted or concentrated closer to the central axis of the ICP as they flow into the discharge. Under the same operating conditions a 40-MHz plasma generates a more intense discharge and yields higher intensity enhancements than does a 27-MHz plasma.
Discrimination among Carbonate Minerals by Raman Spectroscopy Using the Laser Microprobe
Authors: Herman Richard G. , Bogdan Charles E. , Sommer Andre J. , Simpson Dale R.
Published: July 2005

Raman spectroscopy has been used to distinguish the individual carbonate minerals belonging to the calcite, dolomite, and aragonite structural groups. With the use of the in situ laser microprobe technique, it is demonstrated that particle-size effects do not hinder the mineral identification and that high precision in line position is achieved. Spectra can be obtained from samples in any form and provide rapid, nondestructive analyses on a microscopic scale of the hard-to-discriminate carbonate minerals.
Helium Neon Laser Intracavity Photothermal Beam Deflection Densitometer
Authors: Tran Chieu D.
Published: July 2005

A novel, compact He-Ne laser intracavity photothermal beam deflection densitometer has been developed. In this instrument, a TLC plate is placed inside the cavity of the He-Ne laser, which serves as a probe. An argon-ion pump-laser overlaps with the probe beam at the chro-matogram spot. The apparatus is 34 times more sensitive than the corresponding extracavity instrument. The technique not only was able to detect bilirubin, bilirubin ditauride, and half-bilirubin on a developed HPTLC but also provided insight into the photophysical processes of those pigments. The detection limit for bilirubin, excited by the 476-nm laser line, at 20 mW intensity, modulated at 7 Hz, is 2.5 ng.
Investigation of Experimental Parameters with a Quadrupole ICP/MS
Authors: Zhu Guangxuan , Browner Richard F.
Published: July 2005

Preliminary studies have shown that signal behavior in ICP/MS is quite different from that in ICP-OES. This is particularly true for the manner in which ICP operating parameters affect the responses of elements detected, and results from behavior occurring both in the interface and in the mass spectrometer. This paper describes in detail the response of a commercially available instrument (VG PlasmaQuad) to variations in several important operating parameters. The effects of nebulizer flow rate, rf plasma power, and sampling depth on ion populations, on ratios of singly charged to doubly charged ions, and on singly charged ions to oxide and hydroxide ions are described for selected elements. A comparison is also made of the results obtained with the present instrument, with data published from other commercial instrumentation.
Five- and Six-Component Determinations Using Phase-Resolved Fluorescence Spectroscopy and Synchronous Excitation
Authors: Nithipatikom Kasem , McGown Linda B.
Published: July 2005

Multicomponent determinations using phase-resolved fluorescence spectroscopy and synchronous excitation to combine the dimensions of fluorescence lifetime and emission and excitation wavelength are described for five- and six-component systems of spectrally overlapping polycyclic aromatic hydrocarbons. Experimental conditions such as the wavelength intervals scanned, the difference maintained between the emission and excitation monochromators, and the wavelengths and detector phase angles used to generate the data matrices were all generalized rather than optimized for the particular components used in the study. Accuracy was better for the PRFS determinations than for steady-state synchronous excitation determinations using the same number of equations in the data matrix. An average relative error of 0.34% was found for the PRFS determinations of the five-component system, compared with −1.5% obtained for the steady-state determinations, with the use of twenty-four equations. An average relative error of 3.8% was obtained for the PRFS determinations of the six-component system, also with the use of twenty-four equations. The selectivity derived from the fluorescence lifetime dimension in PRFS is therefore shown to be important in multicomponent determinations using generalized conditions for data acquisition and should prove valuable for samples that require both qualitative and quantitative analysis.
Evaluation of a Fourier-Transform-Based Pattern-Recognition Algorithm for Two-Dimensional Fluorescence Data
Authors: Pau Chou-Pong , Warner Isiah M.
Published: July 2005

A pattern-recognition algorithm for two-dimensional fluorescence data previously reported is critically evaluated. The three spectral matching criteria—sum of the absolute value of the imaginary coefficients of the frequency-domain correlation function, sum of the absolute value of the real-negative coefficients of the frequency-domain correlation function, and the intervector distance between the abbreviated Fourier transforms of two spectra—are calculated. Spectra simulated with a computer as well as data acquired with a video fluorometer are examined. Results indicate that all three parameters are sensitive to changes in peak position, peak width, relative peak height, and intensity of background noises.
Evanescent Detection of Adsorbed Protein Concentration-Distance Profiles: Fit of Simple Models to Variable-Angle Total Internal Reflection Fluorescence Data
Authors: Reichert W. M. , Suci P. A. , Ives J. T. , Andrade J. D.
Published: July 2005

Total internal reflection fluorescence spectroscopy (TIRF) is an established technique for following the course of interfacial reactions. Theoretically, by gathering TIRF data as a function of observation angle, one can obtain the density of fluorophores with respect to distance away from a solid/liquid interface. In order that the practical application of the theory might be explored, variable observation angle data from solutions of fluorescein and from adsorbed layers of fluorescein isothio-cyanate labeled immunoglobulin have been analyzed in terms of simple concentration-distance profiles. In all cases the general shape of the data curves was found to conform to the theoretical expectation. Layer thickness determinations varied over a range of 20 to 100 nm, with concentrations in the layer ranging from 12 to 61 mg/mL. The theoretical background, sources of error, and system improvements are also discussed.