bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Cyclobenzaprine on Tricyclic Antidepressant Assays
Authors: Van Hoey Nicole M
Published: June 2005

OBJECTIVE

To evaluate cyclobenzaprine interference on tricyclic antidepressant assays.

DATA SOURCES

Literature was identified through a MEDLINE search (1966–August 2004) using the search terms cyclobenzaprine, tricyclic antidepressant, toxicology, and assay.

DATA SYNTHESIS

Cyclobenzaprine is structurally similar to tricyclic antidepressants and is often identified as a tricyclic antidepressant on toxicology assays. Older chromatographic assays demonstrate retention time differences of only seconds and nearly identical color stains between cyclobenzaprine and individual tricyclic antidepressants. In comparison, ultraviolet absorption ratios of 4.18 for amitriptyline and 1.85 for cyclobenzaprine are easily distinguished. Spectroscopy also consistently identifies cyclobenzaprine's unique mass-to-charge ratio peaks of 275 and 215 compared with those of amitriptyline. Available bioanalytic techniques are reviewed for their ability to correctly identify cyclobenzaprine and differentiate the drug from tricyclic antidepressants.

CONCLUSIONS

When assays are positive for tricyclic antidepressants without a history of their use, an attempt should be made to identify confounders, such as cyclobenzaprine. Newer bioanalytic techniques, such as ultraviolet absorption and mass spectroscopy, accurately identify cyclobenzaprine in such instances.
Relative Thromboembolic Risks Associated with COX-2 Inhibitors
Authors: Jones S Christopher
Published: June 2005

OBJECTIVE

To evaluate the clinical literature on cyclooxygenase-2 (COX-2) inhibitors to determine whether a greater incidence of thromboembolic events is universal within the drug class.

DATA SOURCES

A MEDLINE search was conducted (1996–March 2005) for key articles in the English language assessing the efficacy or safety of these agents.

STUDY SELECTION AND DATA EXTRACTION

Randomized, double-blind, and controlled trials, as well as case–control and retrospective cohort studies, that assessed the cardiovascular safety of COX-2 inhibitors were reviewed.

DATA SYNTHESIS

Seventeen published studies were reviewed, and the cardiovascular safety data were extracted from each trial. The mechanism by which COX-2 inhibitors may induce a thromboembolic event is likely multifactorial involving (1) COX-2–specific isoform binding affinity, (2) drug dose, (3) duration of therapy, and (4) cardiovascular risk profile of the patient. Evidence supports an association between cardiovascular adverse events and the use of rofecoxib, valdecoxib, and celecoxib. However, this risk is not equally distributed among the drugs. Given the relative paucity of data, lumiracoxib and etoricoxib cardiovascular effects remain uncertain.

CONCLUSIONS

Each COX-2 inhibitor has a unique cardiovascular risk profile. Based on the current evidence, celecoxib is the safest COX-2 inhibitor when prescribed appropriately in the lowest possible dose for the shortest duration in the ideal target population.
Evidence-Based Practice by Pharmacists: Utilization and Barriers
Authors: Burkiewicz Jill S , Zgarrick David P
Published: June 2005

BACKGROUND

Evidence-based medicine (EBM) is the use of the current best evidence from research to make practice and policy decisions. Little is known regarding the attitudes of pharmacists toward EBM.

OBJECTIVE

To determine the attitudes of pharmacists toward EBM, the extent that pharmacists use evidence to make decisions, and identify barriers to the use of evidence.

METHODS

A self-administered questionnaire was mailed to 2000 randomly selected Illinois licensed pharmacists. The questionnaire assessed the pharmacists' attitudes toward EBM, the extent to which recommendations are based on primary and tertiary literature, and perceived barriers to the use of EBM.

RESULTS

Completed responses were received from 323 pharmacists (17.2% response rate). Overall, respondents had positive attitudes toward EBM (58% positive, 32% somewhat positive). Respondents thought research findings were useful (42%) or very useful (42%) to daily practice. Nearly one-half (49.8%) of respondents had conducted a primary literature search within the past year. Hospital pharmacists and pharmacists in other practice settings were more likely than community pharmacists to conduct a literature search in the past year (75%, 61%, and 30%, respectively; p < 0.001). Although 86% of respondents reported having Internet access at home, only 42% of all respondents identified that they had PubMed access at home. Common barriers to the use of EBM include lack of time (45%), physician attitudes toward pharmacist recommendations (19%), and access to resources (11%).

CONCLUSIONS

Pharmacist respondents have positive attitudes toward EBM and the application of research findings to practice.
Acute Liver Failure with Renal Impairment Related to the Abuse of Senna Anthraquinone Glycosides
Authors: Vanderperren Bénédicte , Rizzo Michela , Angenot Luc , Haufroid Vincent , Jadoul Michel , Hantson Philippe
Published: June 2005

OBJECTIVE

To report a case of chronic ingestion of very large amounts of senna fruits as an herbal tea, possibly leading to severe hepatotoxicity.

CASE SUMMARY

A 52-year-old woman who had ingested, for >3 years, one liter of an herbal tea each day made from a bag containing 70 g of dry senna fruits, developed acute hepatic failure and renal impairment requiring intensive care therapy. The severity of the hepatic failure was reflected by the increase in prothrombin time (international normalized ratio >7) and the development of encephalopathy. Liver transplantation was discussed, but the patient ultimately recovered with supportive therapy. Renal impairment was consistent with proximal tubular acidosis, also with marked polyuria refractory to vasopressin administration. Suprisingly, large amounts of cadmium were transiently recovered in the urine.

DISCUSSION

Cassia acutifolia and angustifolia plants are widely used as laxatives. Their chronic abuse may be associated with serious manifestations, including fluid and electrolyte loss, with chronic diarrhea. Severe hepatotoxicity is unusual, but could be explained by the exposure of the liver to unusual amounts of toxic metabolites of anthraquinone glycosides (sennosides). An objective causality assessment suggests that hepatotoxicity was possibly related to senna laxative abuse. Regarding nephrotoxicity, there are no available human data on sennosides, while experimental models suggest that anthraquinone derivatives may also accumulate in the kidneys. The finding of high urinary concentrations of cadmium would suggest contamination of the herbal tea by metals, but this hypothesis could not be verified.

CONCLUSIONS

Ingestion of large doses of senna laxatives may expose people to the risk of hepatotoxicity.
Once-Daily Abacavir in Place of Twice-Daily Administration
Authors: Goedken Amber M , Herman Ronald A
Published: June 2005

OBJECTIVE

To review the safety and efficacy of a once-daily dosage regimen for abacavir, a nucleoside reverse transcriptase inhibitor.

DATA SOURCES

English-language MEDLINE and Iowa Drug Information Service database reports were accessed from 1966 to March 2005. International Pharmaceutical Abstracts was searched from 1970 to March 2005. The key words used in all searches were abacavir and Ziagen. Article bibliographies were used to identify additional relevant articles. The Internet was searched to identify abstracts of poster and oral presentations that have not yet been published. The manufacturer was also contacted to obtain unpublished information.

STUDY SELECTION AND DATA EXTRACTION

Publications were included that provided information related to the safety and efficacy of abacavir when used once daily. Preference was given to randomized, double-blind, controlled trials comparing once-daily abacavir regimens with other antiretroviral regimens. Abstracts from professional meetings were included for unpublished studies, and conference coverage reviews were included if the abstracts were not available.

DATA SYNTHESIS

In trials directly comparing once- and twice-daily abacavir, little difference was shown in the efficacy of the 2 regimens. Despite similar adverse effect profiles, significantly more severe hypersensitivity reactions and severe diarrhea were seen with once-daily abacavir in one trial.

CONCLUSIONS

Once-daily administration of abacavir has not been shown to be inferior to twice-daily dosing, but it may put patients at increased risk for severe hypersensitivity reactions and diarrhea. More data are needed to confirm this risk.
Photosensitization by chiral drugs: Looking for stereodifferentiating photoprocesses in the presence of biomolecules
Authors: Lhiaubet-Vallet Virginie
Published: June 2005

Photoreactivity of chiral carprofen (CP) and ofloxacin in the presence of two biomolecules, namely, DNA and human serum albumin (HSA), has been reported. Analysis of the photosensitization of 2'-deoxyguanosine and thymidine (Thd) by high-performance liquid chromatograpy has shown that racemic ofloxacin and levofloxacin [its (S)-stereoisomer] acts by a mixed type I/type II mechanism, while CP does not lead to significant degradation of the nucleosides. Studies on DNA relaxation have revealed formation of single-strand breaks and specific alterations of DNA bases. Ofloxacin and levofloxacin photoinduce direct single-strand breaks and formation of purine and pyrimidine oxidative photoproducts; no Thd dimer has been detected. CP produces only photosensitized single-strand breaks. Moreover, DNA photosensitization has shown a weak enantiodifferentiation in favor of levofloxacin and (S)-CP.

In the case of HSA, a remarkable stereodifferentiation has been found in the interaction between the excited triplet state of CP and protein. Time-resolved laser flash photolysis measurements revealed the presence of two components with different lifetimes that have been assigned to complexation of CP to the two binding sites of albumin. Moreover, photobinding of the drug to protein and formation of the dehalogenated photoproduct of CP proceed via stereodifferentiating photoprocesses.
Bioinspired energy conversion
Authors: Palacios Rodrigo E. , Gould Stephanie L. , Herrero Christian , Hambourger Michael , Brune Alicia , Kodis Gerdenis , Liddell Paul A. , Kennis John , Macpherson Alisdair N. , Gust Devens , Moore Thomas A. , Moore Ana L.
Published: June 2005

Artificial photosynthetic antenna systems have been synthesized based on carotenoid polyenes and polymer-polyenes covalently attached to tetrapyrroles. Absorption of light in the blue/green region of the spectra excites the polyenes to their S2 state, and ultrafast singlet energy transfer to the tetrapyrroles occurs when the chromophores are in partial conjugation. The additional participation of other excited states of the polyene in the energy-transfer process is a requirement for perfect antenna function. Analogs of photosynthetic reaction centers consisting of tetrapyrrole chromophores covalently linked to electron acceptors and donors have been prepared. Excitation of these constructs results in a cascade of energy transfer/electron transfer which, in selected cases, forms a final charge-separated state characterized by a giant dipole moment (>150 D), a quantum yield approaching unity, a significant fraction of the photon energy stored as chemical potential, and a lifetime sufficient for reaction with secondary electron donors and acceptors. A new antenna-reaction center complex is described in which a carotenoid moiety is located in partial conjugation with the tetrapyrrole π-system allowing fast energy transfer (<100 fs) between the chromophores. In this assembly, the energy transduction process can be initiated by light absorbed by the polyene.
Artificial photosynthesis via two-electron conversion: Photochemical oxygenation sensitized by ruthenium porphyrins with water as both electron and oxygen atom donor
Authors: Inoue Haruo , Funyu Shigeaki , Shimada Yutaka , Takagi Shinsuke
Published: June 2005

Recent progress in the field of artificial photosynthesis is reviewed. Among various approaches to oxidizing the water molecule, attention has been focused on the two-electron chemical conversion processes mediated by metallo-porphyrins upon visible light irradiation. Photochemical oxygenation reactions such as the epoxidation of alkenes sensitized by ruthenium(II) porphyrins with water as both electron and oxygen atom donor have been found. Ru porphyrin induces highly efficient two-electron oxidation of water with a quantum yield of 60 % to form an epoxide from the alkene with high selectivity. The water molecule serves as both an efficient electron and oxygen atom donor in the reaction, in which the oxygen atom of water is incorporated in a useful product, i.e., epoxide.
Electronic energy transfer in dinuclear metal complexes containing meta-substituted phenylene units
Authors: D’Aléo A. , Welter S. , Cecchetto E. , De Cola L.
Published: June 2005

The synthesis and photophysical properties of heterometallic dinuclear complexes based on ruthenium and osmium trisbipyridine units, Ru-mPh3-Os and Ru-mPh5-Os, in which the metal complexes are linked via an oligophenylene bridge centrally connected in the meta position, are described. Electronic energy transfer from the excited ruthenium-based component (donor) to the osmium moiety (acceptor) has been investigated using steady-state and time-resolved spectroscopy. The results obtained for the meta-substituted compounds are compared with the analogous systems in which the phenylene spacers are substituted in the para position. The mechanism of energy transfer is discussed.
Experimental and Theoretical Study of Laser-Enhanced Ionization and Dual-Laser Ionization of Sodium Vapor
Authors: Lin K. C. , Lin S. H. , Hunt P. M. , Leroi G. E. , Crouch S. R.
Published: June 2005

An application of the optogalvanic effect in a premixed H2,-O2-Ar flame, called laser-enhanced ionization (LEI), employs a dye laser, which is tuned to resonance with the 3 S1/2-3 P3/2 transition of sodium anal) te. The ionization mechanism is dominated by the collisional process following resonant excitation. With addition of a second N2 laser, the resulting dual-laser ionization (DLI) technique displays enhanced sensitivity; furthermore, the multiphoton ionization process dominates the ionization mechanism. A theoretical model based on the density matrix formalism (or master equation approach) has been employed to interpret ac Stark broadening and intensity dependence observed in Na DLI line shapes, and to determine the ionization rates. The DLI photoionization rate obtained from the model agrees satisfactorily with that produced by other authors. It is well known that the density matrix formalism can properly take into account the collisional effect and the saturation effect observed in the power dependence measurement of DLL
Component Spectrum Reconstruction from Partially Characterized Mixtures
Authors: Nyden Marc R. , Chittur Krishnan
Published: June 2005

A mathematical analysis of some existing approaches to component spectrum reconstruction is presented. This analysis leads to the derivation of a generalization of the cross-correlation technique. The effectiveness of these methods is assessed from the quality of the reconstructions obtained with the use of synthetic mixture spectra. Reconstructions of the spectra of the components of aqueous mixtures of immunoglobulin G and albumin are compared to the corresponding spectral reconstructions of the pure proteins in buffer.
Tandem Helium Plasma Spectrometry with a Capacitively Coupled Discharge Formed above a Helium ICP
Authors: Chan Shi-Kit , Tan Hsiaoming , Montaser Akbar
Published: June 2005

A tandem helium plasma was formed by placing a water-cooled, grounded electrode above a helium inductively coupled plasma (He ICP). The tandem plasma could be operated at 250 to 700 W. Detection limits of F, Cl, Br, S, and C at 500 W were comparable or superior to those from a He ICP operated at 1500 W. At 500 W, the electron number density for the tandem helium plasma was greater than that for the He ICP at 1500 W, but similar excitation temperatures and roughly similar rotational temperatures were obtained.
An FT-IR Study of the Effect of Simulated Solar Radiation and Various Particulates on the Oxidation of SO2
Authors: Smith D. M. , Keifer J. R. , Novicky M. , Chughtai A. R.
Published: June 2005

Short- and long-term studies of the effect of black carbon and other particulates on the oxidation of SO2 with and without the presence of oxygen, water vapor, and simulated solar radiation, have been carried out. FT-IR studies involving isotopic oxygen-18, sulfur dioxide-18, and D2O in these reactions confirm the requirement of water vapor and oxygen for this oxidation. Such experiments conducted at 298 K demonstrate only the formation of ionic sulfates, while the reactions conducted under simulated solar radiation show the formation of both covalent and ionic sulfate species. These observations have implications for the retention or diminution of catalytic activity by the soot. The reaction vessel walls, SiO2, and particulate black carbon, all act as catalysts for the conversion of S(IV) to S(VI), the amounts depending primarily on the surface area of the solid.
Spectroscopic Measurement of Used Lubricating Oil Quality
Authors: Stuart A. D. , Trotman S. M. , Doolan K. J. , Fredericks P. M.
Published: June 2005

Used lubricating oils have been examined by a number of spectroscopic techniques to assess whether it might be possible to improve turn-around time for laboratory analyses or to develop a simple oil quality sensor which could be used in a service workshop. Investigation shows that the development of an oil quality sensor based on discrete wavenumber measurements in the mid-infrared region would not be warranted, but heptane-insolubles can be estimated from a single measurement in the near-infrared region, and this could form the basis of a simple sensor. Considerable information about the quality of a used oil is available through a thorough examination of its mid-infrared spectrum. Use of the computer program CIRCOM, which employs factor analysis followed by multiple linear regression, allowed useful correlations to be obtained for n-heptane—insolubles level and viscosity and total base number of the oil sample. This supplements and extends the previously described methods for obtaining information such as fuel and water levels by IR analysis.
Estimation Errors of Component Spectra Estimated by Means of the Concentration-Spectrum Correlation: Part I
Authors: Uozumi Jun , Asakura Toshimitsu
Published: June 2005

It is shown by theoretical analysis and computer simulations that statistical errors accompany the estimates of component spectra of complex mixtures calculated by the concentration-spectrum correlation method. It is revealed that the estimation errors consist of a superposition of other component spectra, each multiplied by a weighting factor. The weighting factor contains three statistical parameters of the sample: two sample standard deviations of both the objective and the interfering components, and the sample correlation coefficient between these two component concentrations. The probability density function of the weighting factor, as well as its ensemble average and standard deviation, is derived. It is shown that the ensemble standard deviation of estimation errors, which is a good measure for the accuracy of the estimated spectrum, can be estimated by the nonparametric method called a bootstrap. The behavior of the estimation errors and the effectiveness of the bootstrap method are demonstrated by computer simulations.
A Study of the Crossing Angle in Condensed-Phase CARS
Authors: Adachi Yukio , Hirose Chiaki
Published: June 2005

A novel method of tuning the crossing angle, that is, the phase-matching condition, in condensed-phase CARS measurements has been presented. The method enables us to tune the phase-matching condition by simply tilting the sample cell with no need for adjusting the crossing angle of excitation laser beams over the range of about 600 cm−1.To this end, a relation between the crossing angle and the frequency difference between the two excitation lasers, which is associated with the Raman shift, has been derived in the normal dispersion region and has been experimentally examined.
The Possibility of Signal Enhancement in Liquid Absorption Spectrometry with a Long Capillary Cell Utilizing Successive Total Reflection at the Outer Cell Surface
Authors: Tsunoda Kin-Ichi , Nomura Akira , Yamada Joseph , Nishi Sueo
Published: June 2005

A new type of long capillary cell (LCC) for liquid absorption spectrometry, in which incident light is transmitted with successive total reflection at the outer cell surface, has been proposed. An uncoated and uncovered capillary tubing of borosilicate glass showed much better light trans-missivity in aqueous solution as a LCC than did one with mirrored walls, and it could be used in coiled form without attenuation of light. An effective pathlength of 85 cm (at A1 cm = 9 × 10−5) and a baseline stability of 3 × 10−6 AU were obtained with a 90-cm LCC (i.d. 260 μm, o.d. 400 μm, coiled into 14-cm-diameter coil). The calibration curve was nonlinear because of its nature as a multipath cell. The distribution of light energy inside the LCC was estimated by using a simple statistical model based on the Markov chain.
Fourier Deconvolution of Overlapping Line Pairs in Inductively Coupled Plasma-Atomic Emission Spectrometry
Authors: Van Veen Eric H. , Goudzwaard M. Pieter , De Loos-Vollebregt Margaretha T. C. , De Galan Leo
Published: June 2005

A deconvolution procedure utilizing Fourier transformation has been developed to reduce line overlap in ICP-AES. Line broadening is caused by physical processes and by instrumental broadening. Convenient deconvolution, however, turns out to be restricted to broadening common to the emission lines in the spectral window, i.e., to instrumental broadening. Deconvolution for the “true” instrumental broadening function and for a Gaussian approximation to this function yields similar results, but the former allows for fast automated data processing with regard to any spectral region and sample composition. A straightforward procedure is reported for the determination of this function independent of wavelength. At the present noise level, a twofold reduction in linewidth can be achieved for emission lines having a small physical width in comparison to the instrumental width. With data acquired from both a high- and a medium-resolution monochromator, results from overlapping line pairs show linear analytical curves and improved detection limits. Due to the decrease in signal-to-noise ratio on deconvolution, the detection limits measured for isolated lines cannot be attained.
Computer Processing of Tunable Diode Laser Spectra
Authors: May Randy D.
Published: June 2005

A computer-controlled tunable diode laser spectrometer and spectral analysis software are described. The three-channel system records simultaneously the transmission of a subject gas, a temperature-stabilized etalon, and a calibration gas. The software routines are applied to diode laser spectra of HNO3 and NO2 to illustrate the procedures adopted for conversion of raw spectral data to useful transmission and harmonic spectra. Extraction of line positions, absorption intensities, collisional broadening coefficients, and gas concentrations from recorded spectra is also described.
Matrix Effects in Matrix Isolation Infrared Spectroscopy
Authors: Jagannathan S. , Cooper J. R. , Wilkins C. L.
Published: June 2005

A major factor limiting extensive use of matrix isolation gas chromatography-Fourier transform infrared spectrometry is the incompatibility of matrix-isolated spectra with available vapor- or condensed-phase spectral data bases. Here, matrix and surface effects on matrix isolation infrared spectra of organic molecules are investigated. Use of xenon at −215°C (58 K) to obtain matrix isolation spectra that are similar to condensed-phase spectra is demonstrated. Finally, the effect of temperature on reflection-absorption infrared spectra of matrix-isolated molecules is discussed, and guidelines for obtaining and interpreting matrix isolation infrared spectra of gas chromatographic eluants using the existing condensed phase data bases are provided.
An Investigation of Noise Amplitude Spectra Produced by a Direct-Current Plasma
Authors: Monnig Curtis A. , Hieftje Gary M.
Published: June 2005

Noise amplitude spectra for direct-current plasma atomic emission spectrometry (DCP-AES) were acquired. Flicker (1/ f) noise dominates the signal at low frequencies, and white noise prevails at higher frequencies. Broad-band audio-frequency (af) noise was observed in the plasma continuum emission when the nebulizer gas was directed into the discharge. By increasing the electrode-gas flows, it was possible to narrow the frequency range and increase the amplitude of this af noise. The introduction of an easily ionized element into the plasma had little effect on the noise characteristics of the source.
Estimation Errors of Component Spectra Estimated by Means of the Concentration-Spectrum Correlation: Part II
Authors: Uozumi Jun , Asakura Toshimitsu
Published: June 2005

Estimation errors accompanying component spectra calculated by means of the concentration-spectrum correlation method are investigated by theoretical analysis and computer simulations. Discussion is concentrated on a modified version of the method, which operates under the constraint that the sum of all the component concentrations in a sample is unity. In an agreement similar to that for the basic method, which was treated in an earlier paper [Appl. Spectrosc. 43, 74 (1989)], the estimation error consists of a superposition of other component spectra, each multiplied by a weighting factor. In this case, however, the weighting factor is a function of five sample statistics: the averages and the standard deviations of the concentrations of both the objective and the interfering components, and the correlation coefficient of these two components. It is shown again that the nonparametric statistical technique called a bootstrap is useful as a tool of false-true discrimination of the peaks in the estimated spectra.
Development of a Multichannel Turbidimetric-Kinetic Photometer for the Quantitative Determination of Endotoxin
Authors: Oishi Haruki , Hatayama Yasumichi , Fusamoto Masaji , Sakata Yoshitsugu
Published: June 2005

A turbidimetric-kinetic photometer which monitors 64 samples simultaneously and independently has been developed for the automated measurement of endotoxin. This instrument measures the turbidity change at 660 nm in a gelation reaction of the LAL/endotoxin system and automatically scores the reaction time required to obtain a certain turbidity change as gelation time. Since a stationary dry bath incubator controls the reaction temperature of the samples at 37 ± 0.5°C and also controls the ambience of the optical system assembled into the incubator, the objective detection of gelation is provided without any disturbance from sample vibration, and the drift of the detection system is minimized. An extremely wide range for the calibration curve, such as 4 or 5 orders of magnitude of endotoxin concentration, is obtained without sample dilution. The coefficients of variation of the calculated endotoxin concentration are 4.91 to 14.0%.
Signal-to-Noise Considerations in FT-Raman Spectroscopy
Authors: Everall N. J. , Howard J.
Published: June 2005

A simplified theoretical analysis of the S/N performance of Fourier transform (FT) Raman spectrometers compared with conventional scanning machines is presented. Calculations indicate that the multiplex gain may be significantly degraded due to the shot noise from the Raman signal, and this situation is exacerbated when Rayleigh radiation reaches the detector. It is expected that use of detectors with a noise equivalent power of 10−15 W would largely eliminate any multiplex gain in FT-Raman spectroscopy.
Analysis of Pure Lead and Lead Alloys for the Automotive Lead/Acid Battery Industry by Inductively Coupled Argon Plasma Emission Spectroscopy
Authors: Schmitt T. J. , Walters J. P. , Wynn D. A.
Published: June 2005

Pure lead and lead alloy dissolution procedures suitable for elemental determinations by inductively coupled argon spectroscopy are described. The group of lead types investigated consisted of pure lead, Pb-Sb alloys, Pb-Ca-Al alloys, and Pb-Ca-Sn-Al alloys. Major alloy concentrations range up to 10% Sb, 2% Sn, 0.2% Ca, and 0.1% Al. Trace impurities from 0.5 to 10 ppm are determined in pure lead and in several lead alloys. Major and trace element determinations are routinely performed simultaneously with the use of five to seven matrix-matched standards for each alloy type. Accuracy and precision data for certified and internal reference materials are reported. Chemical, spectral, and metallurgical interferences are also discussed.
Exact Interpolation of Apodized, Magnitude-Mode Fourier Transform Spectra
Authors: Keefe C. Dale , Comisarow Melvin B.
Published: June 2005

A procedure is developed for the exact interpolation of apodized, magnitude-mode Fourier transform (FT) spectra. The procedure gives the true center frequency, i.e., the location of the continuous peak, from just the largest three discrete intensities in the discrete magnitude spectrum. The procedure is applicable for the peaks in the apodized magnitude spectrum of a time signal of the form f( t) = cos( ωt) exp(– t/τ). There are no restrictions on the value of the damping ratio T/τ. The procedure is demonstrated for the sine-bell and Hanning windows and is generalizable to other windows which consist of a sum of constants and sine/cosine terms. This includes the majority of commonly used windows.
Laser-Power Dependency of Resonant Two-Photon Ionization in Flames
Authors: Seltzer M. D. , Green R. B.
Published: June 2005

Resonant two-photon ionization competes with laser-enhanced collisional ionization (LEI) in flames to ionize analyte atoms. The predominance of either mechanism for a given element depends on the excitation scheme as well as the level of irradiance. Optical saturation of the resonant transition through which the two-photon mechanism proceeds precludes observation of a second-order dependence of ionization signal on laser power. The laser power dependency of resonant two-photon ionization for a series of elements is examined, and results of diagnostic value regarding the probable ionization mechanisms are obtained.
Fourier Transform Flame Infrared Emission Spectroscopy
Authors: Tilotta David C. , Busch Kenneth W. , Busch Marianna A.
Published: June 2005

The thermal fragmentation of organic compounds in a hydrogen/air flame is studied via Fourier transform flame infrared emission (FT-FIRE) spectroscopy. In this preliminary survey of more than 75 organic compounds, it is shown that compound and element-specific infrared emission bands are produced when organic compounds containing C, H, Cl, F, S, and Si are combusted in the flame. Correlations of these infrared emission bands with possible combustion products are presented.
Simultaneous Determination of Two-Component Mixtures and pHs by Dual-Wavelength Thermal Lens Spectrometry
Authors: Franko Mladen , Tran Chieu D.
Published: June 2005

The recently developed dual-wavelength thermal lens spectrometer, which is capable of simultaneously measuring thermal lens signals at two different wavelengths, has been used to simultaneously determine two-component samples and solution pHs. Compared to conventional absorption spectrophotometry, this dual-wavelength technique offers advantages that include fast data acquisition and higher sensitivity. With the use of 20-mW excitation beams, the limits of detection for the simultaneous determination of ferroin and iron(II) bipyridyl complexes mixtures are estimated to be 3.6 × 10−9 M and 8.4 × 10−9 M, respectively. In addition, the high monochromaticity of the laser makes this technique uniquely suited for the simultaneous determination of two-component samples whose absorption bandwidths are too narrow to be determined by the conventional spectrophotometric method. The limits of detection for the Er3+ and Nd3+ ions in the two-component mixtures are estimated to be 8.9 × 10−4 M and 7.6 × 10−5 M, respectively. Solution pHs have also been sensitively and accurately determined by using this technique to measure the concentrations of the protonated and deprotonated forms of an indicator. Similar to the two-component sample determination, this thermal lens technique is superior to the conventional spectrophotometric method because it is fast, has relatively higher sensitivity, and allows an indicator to be used over a wider pH range. Solution pHs, ranging from 2 to 9, have been determined accurately with this technique, with the use of such indicators as phenol red, methyl orange, and thymol blue, whose concentrations can be as low as 10−9 M.
Development of a Computer-Controlled Versatile Luminescence Spectrometer for Room-Temperature Phosphorescence Spectrometry
Authors: Kim Haidong , Zabik Matthew J. , Crouch Stanley R.
Published: June 2005

An inexpensive, but versatile computer-controlled luminescence spectrometer has been developed for fluorescence, room-temperature phosphorescence (RTP), and RTP lifetime measurements. A continuum xenon-arc lamp was modulated with a rotating single-disk type chopper, and the chopping phase was accurately detected by a simple and flexible circuit. An integrated, menu-driven software package was developed for data acquisition, instrument control, and data manipulation with IBM-XT compatible personal computer. The system developed has a number of advantages, compared with the conventional rotating-can type phosphoriscope, including increased sensitivity, high selectivity, and versatile applicability for short-lived RTP.
Thermal Decomposition of Energetic Materials 33: The Thermolysis Pathway of the Azidodinitromethyl Group
Authors: Cronin J. T. , Brill T. B.
Published: June 2005

Rapid-scan FT-IR studies are reported for the thermal decomposition of R (CH2)3C(NO2)2N3 ( R = CH3OC(O)-, HO-, -OC(O)O-, and O2NO-) at a heating rate of 70°C/s or higher. The thermolysis is initiated by the -C(NO2)2N, group. At 15 psi Ar, a sharp exotherm occurs at about 180°C. Except when R = O2NO-, the gas products are NO2, N2 (inferred), and R(CH2)3CN, making the rapid thermal decomposition one of the most straightforward yet observed for an energetic functional group. At an Ar gas pressure of 500 psi, the products are altered only to the extent that partial oxidation of the organonitrile occurs. The exotherm remains at about 180°C but is greatly accentuated. When R = O2NO-, the thermolysis temperature profile is very similar to the other compounds, but an organonitrile is not detected. Instead, at 15 psi Ar, a mixture of gas products resulting from the reaction of NO, with the backbone is detected, indicating that the nitrate ester also reacts. At 500 psi Ar, the products and thermal profile of this compound are characteristic of an explosion.
The Laser-Induced Nitrations of Several Hydrocarbons
Authors: Stanley A. E. , Godbey S. E.
Published: June 2005

The Army uses nitrated compounds as explosives and propellants. The ability to selectively nitrate materials is a much-needed process. Laser-induced chemistry possesses the potential to drive some reactions in an efficient and selective manner. Laser-induced chemistry may be useful in driving nitration reactions toward specific products. Reported herein are the results of several successful attempts to laser-induce the reaction of nitrogen dioxide with hydrocarbons of 3, 4, and 5 carbons. Specifically, the tunable continuous wave (cw) infrared laser was used to drive the reaction between nitrogen dioxide, NO2, and propane, n-butane, isobutane, and n-pentane. The major products of the reactions were secondary (tertiary in the isobutane reaction) nitrohydrocarbons, of the same chain length as the reacting hydrocarbon. Some short-chain nitrated compounds were also identified. The yield of 2-nitrobutane observed in the nitration of butane is ∼20% on the basis of the depletion of NO2. The propane reacted with NO2 to produce mostly 2-nitropropane with a smaller yield of 5–9%. The analogous reaction of pentane produced ∼9% of the major product, which is believed to be 2-nitropentane. The isobutane nitration resulted in approximately a 10% yield of 2-methyl-2-nitropropane. The results of these laser-induced reactions are contrasted to the corresponding thermal reactions. The reaction mechanism is also discussed for these two processes.
Advantageous Apodization Functions for Absorption-Mode Fourier Transform Spectroscopy
Authors: Lee Judy P. , Comisarow Melvin B.
Published: June 2005

A systematic examination of the efficacy of window functions for reduction of the spectral skirt of absorption-mode Fourier transform spectra is reported. A window which has its maximum at the beginning and its minimum at the end of the time-domain data gives a satisfactory absorption line shape. In contrast, a symmetrical window with its minima at the ends and its maximum in the middle gives an unsatisfactory absorption line shape. These symmetrical windows are satisfactory for apodization of magnitude spectra. The efficacy for reducing the spectral skirt is examined for the general case of a damped time-domain signal, with specific cases ranging from undamped to essentially completely damped signals. The choice of the window is dependent upon the required dynamic range and the amount of damping in the time-domain data. For a dynamic range of 100:1, the Noest-Kort absorption window and the Norton-Beer F3 windows are the windows of choice. For a dynamic range of 1000:1, either the Filler E0.20 window or the Kaiser-Bessel window can be recommended. The sensitivity change accruing from windowing is reported for all windows examined, for a damping range from zero to essentially complete damping
Evaluation of the Time-Resolved Spark for the Determination of Sodium, Potassium, and Calcium in Microsamples
Authors: McDonald John T. , Williams J. C. , Williams James C.
Published: June 2005

This paper describes the evaluation of a time-resolved graphite spark source emission spectrometer built for the purpose of determining Ca, Na, and K in nanoliter volume samples of renal fluid. Subnanogram detection limits calculated from the working curve slope and the uncertainty of the sample signal are reported for Ca, Na and K; these detection limits are some three orders of magnitude higher than the shot noise limit. With the use of Li as an internal standard, working curves from 0 to 1 ng of Na, K, and Ca are shown. System performance data are given, and the utility of the analysis is discussed.
The Introduction of Powdered Solid Samples as Aerosols into the Inductively Coupled Plasma
Authors: Pfannerstill Peter E. , Caruso Joseph A. , Willeke Klaus
Published: June 2005

A powder disperser has been developed in these laboratories for the introduction of powdered solid samples, as aerosols, into the ICP. The operation is based on a two-step process, whereby the formation of the aerosol is separated temporally and physically from the introduction of the aerosol into the ICP. The operating parameters chosen for the PCW-powder disperser determine the period of time that the aerosol is delivered to the ICP. Typical times are between 15 seconds and 2 minutes. The plasma remains stable throughout the experiment. The design and theory of operation of the device are outlined. Preliminary studies are divided into two parts: (1) the optimization of the generation and the delivery of the aerosol to the plasma and (2) the optimization of the plasma operating parameters. Factors affecting the generation and the delivery of the aerosol to the plasma are discussed. The data suggest that this method and device may be applicable for the analysis of finely divided, nonhygroscopic solid samples using ICP-AES; however, it is not practical for use with samples that are not well suited for grinding into small particle sizes, such as alloys.
Measurements of 22Ne-20Ne Isotope Shifts by Laser-Induced Line Narrowing in Three-Level Systems
Authors: Ståhlberg B. , Jungner P. , Fellman T.
Published: June 2005

Application of laser-induced absorption line narrowing (ALN) to neon isotope shift investigations in the stretched three-level systems 1 s5-2p4-3 s2 and 1 s4-2 p4-3 s2 is reported. The measurements have been performed with a frequency and intensity-stabilized 633-nm He-Ne probe laser and with a tunable single-mode R6G dye laser. Utilization of longitudinal magnetic modulation to the neon gas absorber yields background-free resonance signals. Measurements of 594.5-, 609.6-, and 633-nm 22Ne-20Ne isotope shifts result in (1712 ± 8) MHz, (1753 ± 8) MHz, and (904 ± 8) MHz, respectively. These values agree with previous data.
A Comparative Study of Electron Density Determination Methodologies in the Helium Microwave-Induced Plasma
Authors: Workman John M. , Fannin Harry B. , Brown Peter G. , Caruso Joseph A.
Published: June 2005

Electron number densities were examined in a low-power atmospheric-pressure helium microwave-induced plasma. Two hydrogen-based methods and two helium-based methods were employed to estimate electron concentration. The hydrogen 4471 Å Balmer line was examined with the use of both line shape and full width at half-maximum intensity measurements. The data suggest that half-width calculations underestimate electron densities. Half-width measurements of neutral helium lines result in number densities which appear to be overestimated. This inaccuracy is thought to be the result of apparatus broadening. Finally, the use of quasi-degenerate helium neutral lines possessing forbidden and allowed components afforded electron concentrations similar to those derived from the Balmer beta line shape analysis.
TXRF Spectrometric Analysis of Major Elements in Mineral Sands
Authors: Yap C. T. , Gunawardena K. V. R.
Published: June 2005

The major elements of mineral sands such as rutile and ilmenite vary widely in their concentrations. A method is developed with the use of thin-film samples and the total reflection x-ray fluorescence technique to obtain quantitative concentrations of such samples. The method was tested with the use of the GSJ (Geological Survey of Japan) rock reference JB-3, and agreement with quoted values was good. The advantages of the method are the simplicity of sample preparation, including easy removal of samples from the reflector; the low background contribution from the substrate; and the small quantity of the sample that is required.
A Fast Spectrum-Recovery Method for Hadamard Transform Spectrometers Having Nonideal Masks
Authors: Dyer S. A. , Harms B. K. , Park J. B. , Johnson T. W. , Dyer R. A.
Published: June 2005

A computationally inexpensive method is presented for the recovery of spectra from measurements obtained with Hadamard transform spectrometers having nonideal masks. Normally, N measurements are required in order to recover an N-point spectrum; this method requires N + N0 measurements to be taken, where, typically, N0 ≤ 10. Once the additional measurements have been taken, only O( N[log2 N + 2]) arithmetic operations—mostly additions or subtractions—are needed in order to recover the spectrum; a conventional procedure requires O(2 N2) operations. Preliminary work for this method is minimal, requiring O( N) operations as opposed to O( N3) for a conventional procedure; this work needs to be done only once for a given spectrometer. The spectrum-estimate obtained is unbiased.
Variable-Temperature Study of Syndiotactic Polystyrene
Authors: Nyquist Richard A.
Published: June 2005

IR data are presented which indicate that syndiotactic polystyrene exists in different crystalline forms at ambient temperature, depending upon its physical history.
Infrared Studies of “Hard” and “Soft” Woods
Authors: Owen N. L. , Thomas D. W.
Published: June 2005

FT-IR spectra of 24 different woods have been studied with the use of whole wood pieces and a diffuse reflectance accessory. Three absorptions have been identified, the positions or relative intensities of which are characteristic of the holocellulose/lignin ratio or of the type of lignin present in the wood. These spectral features serve as useful indicators to distinguish between “soft” or “hard” woods.
Some Novel Applications of an Infrared Microscope
Authors: Bergin F. J.
Published: June 2005

In recent years there has been considerable growth in the use of infrared microscopy as an analytical tool. These applications have focused on the spatial resolving power of the microscope for analysis of small samples or small contaminants or inhomogeneities within a material. The infrared microscope can also serve as a more versatile sampling accessory. Depending on the nature of the material under investigation, diffuse reflectance or true specular reflectance spectra can be recorded from bulk polymeric materials. In either case, useful chemical or functional group information can be obtained in a noninvasive and nondestructive manner. As a further example of the versatility of the infrared microscope, some initial results are presented illustrating its potential use in the study of monomolecular films on aqueous substrates.
Correction for Absorption in Raman Measurements Using the Backscattering Geometry
Authors: Womack James D. , Mann Charles K. , Vickers Thomas J.
Published: June 2005

Correction for sample absorption in resonance Raman measurements employing the backscattering geometry has been re-examined. A widely used procedure [see Appl. Spectrosc. 28, 319 (1974)] fails to provide adequate correction under most measurement conditions. A method which accounts for the effect of the transfer function of the collection optics is shown to provide excellent results for a variety of measurement conditions. The required calculations and a method for obtaining the optical transfer function are described. Measurements on solutions of a strongly absorbing azo dye with the use of 514.5-nm excitation have been used to test the approaches.
Analytical Characteristics of a Spark-Sampled/Pulsed Radio-Frequency Re-Excited Analytical Discharge
Authors: Sainz Mario A. , Coleman David M.
Published: June 2005

A high-voltage analytical spark is used to “sample” a metallic electrode and to convert that sample into a desirable form (toroidally shaped post-atomic vapor). This sample is then inductively re-excited with a short burst of radio-frequency (200 MHz) energy. Emission resulting from this re-excitation process is simplified, is free from background continuum, and shows narrow linewidths, when compared with direct spark emission. Analytical working curves for lead and iron in copper-based alloys show good linearity and range. Detection limits of 10 ppm are also shown for several elements in metallic samples.
Infrared Study of Styrene-4-Methylstyrene Copolymers
Authors: Nyquist R. A. , Malanga M.
Published: June 2005

Two types of crystalline syndiotactic polystyrene units are observed in these styrene- p-methylstyrene copolymers. The low-temperature crystalline form is observed in copolymers containing 2 weight percent or less 4-methylstyrene, and the high-temperature crystalline form is observed in copolymers containing 3 to 7 weight percent 4-methylstyrene. Quantitative analysis of styrene-4-methylstyrene copolymers can be performed with the use of infrared spectroscopy and an infrared absorption band intensity ratio technique.