Preparation and Pharmacokinetic Evaluation of Iodine-125 Labeled Alphamethyl-L-Tyrosine

A prompt gamma-ray neutron activation analysis (PGNAA) system was used to calibrate and validate a Monte Carlo model as a proof of principle for the quantification of chlorine in soil. First, the response of an n-type HPGe detector to point sources of ⁶⁰Co and ¹⁵²Eu was determined experimentally and used to calibrate an MCNP4a model of the detector. The refined MCNP4a detector model can predict the absolute peak detection efficiency within 12% in the energy range of 120–1400 keV. Second, a PGNAA system consisting of a light-water moderated ²⁵²Cf (1.06 g) neutron source, and the shielded and collimated HPGe detector was used to collect prompt gamma-ray spectra from Savannah River Site (SRS) soil spiked with chlorine. The spectra were used to calculate the minimum detectable concentration (MDC) of chlorine and the prompt gamma-ray detection probability. Using the ²⁵²Cf based PGNAA system, the MDC for Cl in the SRS soil is 4400 g/g for an 1800-second irradiation based on the analysis of the 6110 keV prompt gamma-ray. MCNP4a was used to predict the PGNAA detection probability, which was accomplished by modeling the neutron and gamma-ray transport components separately. In the energy range of 788 to 6110 keV, the MCNP4a predictions of the prompt gamma-ray detection probability were generally within 60% of the experimental value, thus validating the Monte Carlo model.     

Trace analysis of chlorine in high-purity refractory metals with isotope dilution mass spectrometry

Summary A method for the determination of chlorine in high-purity molybdenum and tungsten with isotope dilution mass spectrometry (IDMS) has been developed using a ³⁷Cl enriched spike solution. After dissolution of the sample in H₂O₂, chlorine is separated by AgCl precipitation. Negative Cl^- thermal ions are produced in a double-filament ion source using an easy-to-handle and cost-efficient quadrupole thermal ionization mass spectrometer. The detection limit, which is mainly influenced by contaminations from the laboratory air, lies between 0.006 and 0.1 g/g depending on the variation of the blank values. Chlorine concentrations between 0.07 and 10.5 g/g are analysed in different tungsten and molybdenum samples. A comparison with other sensitive analytical methods shows the urgent necessity of developing alternative methods for the determination of chlorine traces in refractory metals.Dedicated to Professor Dr. V. Krivan on the occasion of his 60th birthday     

Measurement of arsenic in sectioned hair samples by instrumental neutron activation analysis

In a recent Texas murder case, bundles of head hair from the female victim (aligned with all root ends together) were washed, cut into 7 mm sections, air-dried and weighed, activated in a nuclear reactor neutron flux, and then counted with a Ge(Li) detector/4096-channel gamma-ray spectrometer. In each of the 15 samples, the 559 keV gamma-ray peak of 26.3 hour⁷⁶As was measured. In the section closest to the scalp, an arsenic concentration of 107 ppm was found (cf. a normal level of about 1 ppm As). Barium ingestion was also possible so Ba was looked for, but not found. The victim's husband was found guilty of murder by chronic arsenic poisoning.     

Determination of the fluoride distribution in rabbit bone using instrumental neutron activation analysis

An instrumental neutron activation analysis (INAA) technique, based on the¹⁹F(n,)²⁰F reaction, has been development for the determination of fluoride in bone. The purpose was to study fluoride distribution in different kinds of bone samples using a rabbit model. The rationale for the study stems from the posible correlation between fluoride in bone and osteoporosis. The sodium concentration in the bone was used to correct the²⁰F peak area for the²³F(n,)²⁰F contribution. Two secondary standards, teflon tape and teflon coated dacron line, were used to quantify fluoride concentration. They proved to be stable and consistent with respect to their fluoride concentration. Bone specimens from 10 sites and two tooth samples were analyzed for fluoride. Fluoride concentration ranged from 305 ppm in the tibia long bone to 585 ppm in the humerus trochanter end and the magnitude of fluoride concentration levels is age depdentent. The detection limit of the fluoride is approximately 5 ppm using a 100 mg bone sample.     

High resolution prompt (n,γ) spectroscopy using a down hole logging tool

A down-hole logging tool is described utilising a 5 Ci²⁴¹Am–Be neutron source and intrinsic germanium gamma-ray detector. The tool was used to measure the prompt gamma-ray response from the irradiation of 4 well characterised coal samples. The correlation between the count-rate into the 2380 keV line arising from sulphur and the sulphur concentration as determined by chemical analysis is described. A depression in the count rate into the sulphur peak of interest is modelled using the neutron transport code ANISN and compares well with measurement. The influence of borehole diameter and the presence of borehole fluid upon logging performance is assessed.     

Determination of praseodymium in lanthanum compounds by neutron activation and ion exchange separation

Summary A procedure was developed to determine small amounts of praseodymium in lanthanum compounds by neutron activation analysis. After irradiation of the sample in a reactor praseodymium is separated from lanthanum by anion exchange and Pr-142 is measured by a gamma-ray spectrometer. From the high decontamination factor of 110⁸ a detection limit of 5ppb praseodymium in lanthanum may be calculated. Because of the strong activation of lanthanum, the handling of samples with activities of about 1 Ci La-140 would be required. For the analyses carried out here with respect of sample weights, neutron flux and irradiation time a detection limit of 2.4ppm was obtained.

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Bestimmung von Praseodym in Lanthanverbindungen durch Neutronenaktivierung und Ionenaustausch

Zusammenfassung Zur Bestimmung von geringen Mengen Praseodym in Lanthanverbindungen wurde ein auf Neutronenaktivierungsanalyse basierendes Verfahren entwickelt. Nach Bestrahlung der Probe im Reaktor wird Praseodym mit einem Anionenaustauscher von Lanthan getrennt und Pr-142 mit einem Gamma-Spektrometer gemessen. Der mit der Trennung erreichte Reinigungsfaktor von 110⁸ würde eine Nachweisgrenze von etwa 5ppb Praseodym in Lanthan erlauben. Wegen der starken Aktivierung des Lanthans würde das aber den Umgang mit Proben von ca. 1 Ci La-140 erfordern. Mit den hier gewählten Probenmengen, Neutronenflüssen und Bestrahlungszeiten wurde eine Nachweisgrenze von 2,4ppm erreicht.

Presented at the Ulmer Symposium Analytische Chemie — Elementanalyse mit chromatographischen Methoden, Sept. 19–21, 1979, D-7900 Ulm     

Halogen aggregation in chlorobenzene-<Emphasis Type="Italic">o</Emphasis>-dichlorobenzene solutions

The chlorobenzene (CB)–o-dichlorobenzene (o-DCB) liquid system has been studied by classical molecular dynamics simulation over the entire range of concentrations. The structure of the solutions is characterized by using radial angular distribution functions for the distances between the planes of benzene rings and the angle between them, using radial distribution functions for the distances between chlorine atoms, and by calculating the self-diffusion coefficients and local dipole moments. Halogen aggregation in the pure components and solutions is analyzed. It is found that in pure CB, chlorine aggregates consisting of four to ten molecules are most likely to form. The sizes of chlorine aggregates increase with increasing o-DCB concentration, and at a o-DCB concentration of 0.50-1.00 ppm, an extended system of chlorine–chlorine contacts is formed. In pure o-DCB, the chlorine aggregation system includes 99% of the molecules of the simulated system. The agglomeration of solute molecules in the range of dilute solutions (x < 0.1 ppm) is investigated.     

Product formation in the association reaction of ClO with NO2 investigated by diode laser kinetic spectroscopy

Diode laser spectroscopy has been employed to monitor the formation of chlorine nitrate (ClONO₂) in the association reaction of ClO with NO₂. Chlorine nitrate is the only stable end-product of this reaction at room temperature. Time-resolved measurements of ClONO₂ formation using molecular modulation showed no evidence for any involvement of unstable isomers of ClNO₃ in the reaction. These measurements gave a value of k₁ = (1.8 ± 0.4) × 10^?31 cm⁶/molecule² · s for the reaction at 295 K and an upper limit of 5 ms for the lifetime of any isomeric products at this temperature.     

Determination of nitrogen in pork meat using in-vivo prompt gamma-ray activation technique

The concentration of nitrogen in pork meat is determined by in-vivo prompt gamma-ray activation analysis using the reactor neutron beam and a high purity germanium gamma-ray spectrometer. The photopeak area of the 10827 keV high energy prompt gamma-ray, originated from¹⁴N(n, ) reaction on the pork medium, is analyzed to determine the concentration of nitrogen. Urea solutions with various concentration of nitrogen are used to calibrate the absolute efficiency of the gamma-ray spectrometer. In 9000 s irradiation and counting period, the minimum detectable concentration is 1.7 g of N/100 g of meat using the in-vivo technique. The result is also compared to data obtained by another analytical method. This nondestructive, in-vivo technique, with nominal radiation dose, is a reliable and promising method to determine the nitrogen concentration in living body.     

F and C spectra of fluorinated and partially fluorinated vinyl alkyl ethers

Fluorine, hydrogen, and ¹³C NMR spectral data have been obtained for vinyl alkyl ethers containing fluorines. Some of the molecules are perfluorinated and others include hydrogen, bromine, and chlorine substituents. New generalizations regarding FF spin-spin coupling are developed and used, along with previously recognized correlations, in the confirmation of structures and the assignments of resonances. ¹³C spectroscopy, especially the analysis of ¹³C¹⁹F coupling, is critical in several of the structure determinations. Chlorine isotope effects on fluorine chemical shifts are observed when the chlorine and fluorine are attached to the same carbon, and are also used in the structure analyses. Long-range couplings between fluorines in the vinyl group and fluorines in the alkyl group are interpreted in terms of molecular geometry which allows certain of the alkyl fluorines to “touch” the fluorines cis and gem to the ether oxygen but not the fluorine trans to the oxygen. Two bond ¹³C¹⁹F coupling across the vinyl double bond is found to vary dramatically with the electronegativity of the vinyl substituents in the ethers, in accordance with previous observations for olefins.     

Photometrische Bestimmung von kleinen Mengen Chlorid in Selen, Tellur, Gallium und Wismut

Zusammenfassung Die Probe wird mit Salpetersäure in Gegenwart von Silbernitrat gelöst. Das entstandene Silberchlorid trennt man durch Zentrifugieren ab und zersetzt es anschließend mit Chromschwefelsäure in einer Bestimmungsapparatur. Dabei entstehende flüchtige Chlorverbindungen werden in einer schwefelsauren Kaliumpermanganatlösung zu Chlor oxydiert, das mit o-Tolidin ein gelbes Oxydationsprodukt bildet. Die Extinktion dieser Gelbfärbung wird photometrisch gemessen und die entsprechenden Chloridmengen an Eichgeraden ermittelt. 1–100 g Chlorid können bestimmt werden. Die Standardabweichung beträgt für den Bereich 1–10 ppm maximal ±0,6 ppm Cl und bei der Bestimmung von etwa 200 ppm maximal ± 2,8 ppm Cl.

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Photometric determination of small amounts of chloride in selenium, tellurium, gallium and bismuth

The sample is dissolved in nitric acid in presence of silver nitrate. The silver chloride is separated by centrifuge and decomposed in a glass equipment by chromosulphuric acid. Resulting volatile compounds of chlorine are oxidized by potassium permanganate in sulphuric acid solution to chlorine, which forms with o-tolidine a yellow oxidation product. The absorbance of this coloration is measured by photometry and corresponding amounts of chloride are found out by calibration curves. 1 to 100 g of chloride can be determined in the range of 1 to 10 ppm Cl with a standard deviation of ±0.6 ppm Cl and at approximately 200 ppm Cl with ± 2.8 ppm Cl.

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Wir danken Herrn Dr. G. Iwantscheff, Forschungslaboratorien der Siemens AG, für wertvolle Anregungen und Herrn Dr. v. Sturm, Forschungslaboratorien der Siemens AG, für die Überlassung von polarographisch ermittelten Chlorgehalten in Selenproben.     

Spectrophotometric determination of beryllium and zirconium using chromotrope-2C

Summary Disodium salt of o-carboxyphenylazo chromotropic acid (chromotrope 2C) has been used for the colorimetric determination of microamounts of beryllium and zirconium. The red-violet complexes show maximum absorption at 580 nm and the colour systems obey Beer's law from 0.025 to 0.375 ppm of beryllium and 2 to 12 ppm of zirconium. The optimum concentration ranges are from 0.125 to 0.375 ppm for beryllium and from 4 to 12 ppm for zirconium, where the percent relative errors per 1% absolute photometric error are, respectively, 3.014 and 3.22. The sensitivity of the reactions per cm² are 0.00067 g Be and 0.027 g Zr. The complexes, with the metal to reagent ratio of 11, have instability constants as 2.836 · 10^–6 for beryllium and 6.026 · 10^–6 for zirconium.     

Chlorine-contaminated anode and cathode PEMFC-recovery perspective

Progressive thinking about future generation proton exchange membrane fuel cells (PEMFCs) leads us to cost-effective compact fuel cells operating with dry reactants using self-humidifying membranes. Presently, however, PEMFCs are limited by number of factors. One such factor is the reactant impurities present in the feed streams. Chlorine is one such impurity affecting both anode and cathode PEMFC adversely. Several studies have reported adverse impact of anionic chloride in PEMFCs but scarce or no literature is available on the effect of chlorine gas as such on PEMFCs. In the present work, we report for the first time to the best of our knowledge the adverse effects of chlorine when introduced on anode and cathode independently using a single-cell PEMFC. About 94% (anode) and 82% (cathode) loss in performance is observed at an operating voltage of 0.6 V after contamination with 100 ppm chlorine at the anode and cathode respectively. It is found that operating at higher current density plays a significant role in the PEMFC recovery process. The duration of recovery changes for anode-contaminated cell and cathode-contaminated cell, which is 2 and 4 h respectively. The protons on the anode side and the hydroxyl ion at the cathode side help in replacing the chloride species adsorbed on the platinum surface. The electrochemical impedance studies show an increase in the charge transfer resistance after cathode contamination, whereas in the case of anode contamination, the cell resistance increases while maintaining the same charge transfer resistance.

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Graphical abstract Schematic showing the recovery process of platinum surface by the removal of chloride ion during operation of the cell at 0.1 V

     

High accuracy determination of235U in nondestructive assay standards by gamma spectrometry

High precision gamma spectrometry measurements have been made on five sets of uranium isotope abundance reference materials for nondestructive assay (NDA). These sets are intended for international safeguards use as primary reference materials for the determination of the²³⁵U abundance in homogeneous uranium bulk material by gamma spectrometry. The measurements were made to determine the count rate uniformity of the²³⁵U 185.7 keV gamma-ray as well as the²³⁵U isotope abundance for each sample. Since the samples were packaged such that the U₃O₈ is infinitely thick for the 185.7 keV gamma-ray, the measured count rate was not dependent on the material density. In addition, the activity observed by the detector was collimated to simulate calibration conditions used to measure bulk material in the field. The sample-to-sample variations observed within the 5 sets of samples ranged between 0.005–0.11% (1s) with standard deviations of the mean ranging from 0.01–0.02%. This observed variation appears to be due predominantly to counting statistics and not to material inhomogeneity and/or packaging. The results of this study indicate that accuracy of²³⁵U determinations via gamma spectrometry, in the range of few hundredths of a percent (2), is achievable. The main requirement for achieving this level of accuracy is a set of standards whose²³⁵U isotope abundances are known to within 0.01% (2).     

A galvanic gas sensor using poly (ethylene oxide) complex of silver trifluoromethane sulphonate electrolyte

Summary A galvanic sensor for monitoring nitrogen dioxide was developed by using a poly(ethylene oxide) complex of silver trifluoromethanesulphonate electrolyte. The sensor, which is expressed as Au/P(EO)_4.5 AgCF₃SO₃/Ag, is a small disk (i.d. 13 mm). The polymeric electrolyte film was made by casting the mixture of acetonitrile solutions of both P(EO) (MW 6×10⁵) and AgCF₃SO₃. The working electrode was made by sputtering of gold in argon. The thicknesses of the desposited gold, polymeric electrolyte film and silver are 25 nm, 30 m and 1 mm, respectively. When the sample gas containing nitrogen dioxide impinges at 20 ml min^–1 on the gold cathode, the current flowing in the external circuit was linearly related to the concentration of nitrogen dioxide from 20 ppb to about 10 ppm. The current efficiency of the cell was 0.051%. The cell's response time was about 2 min for 0.5 ppm of nitrogen dioxide.     

Densities and apparent molal volumes of aqueous CaCl2 and MgCl2 solutions

The Pitzer ion interaction model has been used to evaluate literature data for the densities of aqueous CaCl₂ and MgCl₂ solutions between 0 and 100°C. The selected data can be adequately fitted by setting ^(1),v equal to zero. The variations of ^(0),v and C ^v with temperature have been found to be linearly correlated. The uncertainty in the calculated density is lower than 50 ppm below 1M but raises to 300 ppm at high concentrations. When plotted vs. the square root of the molality, the apparent molal volume of MgCl₂ shows a change at a concentration where a transition in the speed of sound has already been reported by Millero, et al.     

O-carboxyphenyl azo chromotropic acid (sodium salt) as an analytical reagent

Summary 0-carboxyphenyl azo chromotropic acid (sodium salt), named as chromotrope 2 C, is used as a new colorimetric reagent for the determination of micro amounts of thorium and aluminium. The blue-violet and red-violet complexes show maximum absorption at 590 nm and the colour systems obey Beer's law from 0.1 to 8 ppm for thorium and 0.1 to 1ppm for aluminium. However, their optimum concentration ranges are from 1.6 to 8 ppm for thorium and 0.2 to 0.8 ppm for aluminium, where the percent relative errors per 1% absolute photometric error are, respectively, 3.06 and 2.94. The composition of the complexes, as elucidated by the continuous variation method, suggests a metal to reagent ratio of 23 for thorium and a ratio of 11 for aluminium. The instability constants for the complexes are of the order of 4.044×10^–10 and 1.006 × 10^–6 at 30°C.Part I, see Z. analyt. Chem. 174, 197 (1960)     

Spectrophotometric determination of iron with chelidamic acid

Summary Chelidamic acid forms with iron a complex at p_H 5.8 to 8.5 having the maximum absorption at 460 nm. The metal to reagent ratio is 13 and the instability constant is about 8.21 · 10^–15. The complex obeys Beer's law from 0.4 to 16 ppm of iron and the optimum concentration range is 1 to 8 ppm, with a relative analysis error of 2.3% per 1% absolute photometric error.

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Zusammenfassung Chelidamsäure bildet mit Eisen beiph 5,8–8,5 einen Komplex, der bei 460 nm ein Absorptionsmaximum aufweist. Das Verhältnis Metall: Reagens beträgt 13, die Instabilitätskonstante etwa 8,21 · 10^–15 Das Beersche Gesetz wird im Bereich von 0,4–16 ppm befolgt, der optimale Konzentrationsbereich liegt bei 1–8 ppm. Der relative Fehler beträgt 2,3% je 1% absoluten photometrischen Fehler.

     

Extraction spectrophotometric investigation of mixed ligand complex of molybdenum(V) with thiocyanate and 4-acetyl-2-(acetylamino)-5-dimethyl-Δ2-1,3,4-thiadiazole

A sensitive spectrophotometric method is developed for the determination of small amounts of molybdenum based on the extraction of molybdenum-thiocyanate-4-acetyl-2-(acetylamino)-5-dimethyl- ²-1,3,4-thiadiazole complex into chloroform from hydrochloric acid medium which is orange red in colour. The complex has an absorption maximum at 470 nm with a molar absorptivity of 2.01×10⁴l·mole^–1·cm^–1. Beer's law is valid over the concentration range 0.06–2.5 ppm of molybdenum with an optimum concentration range of 0.15–2.2 ppm. The ternary complex is stable for over one week at room temperature. Equilibrium shift method indicates 142 composition for molybdenum-thio-cyanate-4-acetyl-2-(acetylamino)-5-dimethyl- ²-1,3,4-thiadiazole complex. The effects of acidity, reagent concentrations, time, temperature and diverse ions upon the absorbance of the complex are critically assessed. This method has been used successfully for the determination of molybdenum in molybdenum steels.     

Chlorine and bromine contents in tobacco and tobacco smoke

The chlorine and bromine contents in tobacco and tobacco smoke in both the particulate and gaseous phases were studied by neutronactivation analysis. Methyl chloride and methyl bromide concentrations were measured in the gaseous phase by gas-liquid chromatography — mass spectrometry. The chlorine and bromine contents in nine brands of cigarettes were on the average as follows: Tobacco—6600 ppm chlorine and 110 ppm bromine. Cigarette smoke, particulate phase—68 g chlorine and 1 g bromine per cigarette. Cigarette smoke, gaseous phase—90 g chlorine and 5 g bromine per cigarette. In the gaseous phase methyl chloride accounted for 60% of the total chlorine and methyl bromine for 80% of the total bromine.