Mass spectrometric determination of cadmium in i.a.e.a. fish solubles

The cadmium content of the I.A.E.A Fish Solubles [A-6 (1975)] was determined by the isotope dilution method. After dry-ashing and dissolution of the specimen, the cadmium was equilibrated with a known amount of ¹⁰³Cd spike, isolated by ion exchange, purified by dithizone extraction, and converted to the sulfide form in 1% H₃PO₄ solution. The CdS precipitate was loaded onto a baked single rhenium filament for mass spectrometric analysis. The ¹⁰³Cd/¹¹⁰Cd ratio was measured to compute the cadmium content of 0.278 ± 0.032 ppm (dry weight basis) in the Fish Solubles.     

Calibration coefficient of a heat-flow DSC. Part I. Relation to the Sensitivity of a thermocouple

Relation between the calibration coefficient of a DSC sensor k(T) and the sensitivity of a thermocouple e(T) which the sensor is made from was derived from the analysis of a heat transfer inside a DSC cell. Ratio e(T)/k(T) is equal to A+BT ³. The first component depends on heat conduction and the second one on radiation. The relationship was tested for DSC-204 Netzsch using (i) data on calibration vs. enthalpies of phase transitions (reference samples) and (ii) measurements of heat capacity of corundum. Both tests show very good agreement between experimental data and predicted theoretical function. This revised version was published online in July 2006 with corrections to the Cover Date.     

Organophosphorus chemistry. Part 18. Possible intervention of a phospha-alkene in the reactions of a fluoroalkylphosphine with alkoxides

Thermal reactions of phenylphosphine with tetrafluoroethylene and 1,1-difluoroethylene give, respectively, a mixture of phenyl-1,1,2,2-tetrafluoroethylphosphine and 1,2-bis-(phenylphosphino)tetrafluoroethane, and phenyl-2,2-difluoroethylphosphine. The phenyltetrafluoroethylphosphine reacts with an excess of ethanolic or methanolic alkoxide to give the corresponding alkyl phenyl-($\text{E}$)-1-fluoro-2-alkoxyvinylphosphinite and minor amounts of the isomeric alkyl phenyl-($\text{Z}$)-2-fluoro-2-alkoxyvinylphosphinite. The use of an equimolar proportion of sodium methoxide enables the intermediate products methyl phenyl-1,2,2-trifluoroethylphosphinite and methyl phenyl-($\text{E}$)-1,2-difluorovinylphosphinite to be isolated: further reaction of these with methoxide yields the corresponding ($\text{E}$)-1-fluoro-2-methoxyvinylphosphinite. The reactions are discussed in terms of mechanisms which involve either an intermediate phospha-alkene or a hydride ion shift.     

Rosa spp. Extracts as a Factor That Limits the Growth of Staphylococcus spp. Bacteria,a Food Contaminant

Due to their richness of bioactive substances, rose hips are a valuable raw material for obtaining extracts with potential antimicrobial activity. The aim of the study was to determine the antagonistic potential of whole pseudo-fruit and flesh extracts of three Rosa sp. varieties against Staphylococcus spp. bacteria isolated as food contaminants. The biological material in this study consisted of seven strains of bacteria from the genus Staphylococcus. Two strains—Staphylococcus aureus ATCC 25923 and Staphylococcus epidermidis DSMZ 3270—were used as reference strains. The other five strains were food-derived isolates—S. epidermidis A5, S. xylosus M5, S. haemolyticus M6, S. capitis KR6, and S. warneri KR2A. The material was the pseudo-fruits of Rosa canina, Rosa pomifera Karpatia, and Rosa rugosa. The polyphenols were extracted from the fleshy part and the whole pseudo-fruit for all rose varieties. The tested preparations differed significantly in their polyphenol composition. The sum of polyphenols ranged from 28 862 to 35 358 mg/100 g of lyophilisate. The main groups of polyphenols found in the preparations were flavanols and ellagitannins. All of the tested extracts inhibited the growth of staphylococci at a concentration of 500 mg/mL. Rosa rugosa fruit extract showed the strongest antimicrobial properties among the studied extracts. For all the strains, the growth inhibition had a diameter of 20.3–29.0 mm. Moreover, six out of the seven tested strains showed the highest inhibition with the use of this extract. The MIC of rose extracts was in the range of 3.125–500 mg/mL and was strictly dependent on the bacterial species, the species of the rose, and the part of the fruit from which the extract was obtained. Correlations were assessed between the main groups of polyphenols in the extracts and their inhibition of bacterial growth. In the case of pseudo-fruit extracts, the inhibitory effect on bacterial growth positively correlated with the content of ellagitannins, and this effect was observed for almost all the tested strains. The results presented herein follow the current trend of minimising the use of chemical preservatives in food; from this point of view, rose extracts are very promising.     

Thermolysis of the [a.2.2]propellanes. Mechanisms for the thermolysis of bicyclo[2.2.0]hexanes.

The thermolysis of the [4.2.2]propellene proceeds with good first order kinetics and gives E_a = 46 kcal/mole. The increase in E_a over that for bicyclo[2.2.0]hexane and the [2.2.2]propellane provides evidence tor the mechanism of these thermolyses.     

Qualitative separations on a microscale. Analysis of the gold group of A. A. Noyes and W. C. Bray

Summary A procedure for the microqualitative analysis of the gold group ofA. A. Noyes andW. C. Bray is presented. The scheme provides for the isolation, estimation and confirmation of 10 micrograms of any member of the group in the presence of 100 micrograms of any other member. In the conversion of the procedure to the micro scale, the ethyl acetate extraction of gold is retained, if mercury is absent; in the presence of mercury, however, the gold is first precipitated with sodium nitrite, and this is followed by the separation of mercury withReinecke's Salt. The method ofGilchrist andWichers is adopted for the separation of the platinum from palladium, rhodium, and iridium by hydrolytic precipitation of the oxides or hydrated oxides of the last three. Rhodium is separated from iridium by precipitation with either potassium nitrite or potassium ethyl xanthate. New tests for palladium, rhodium, and iridium are used. The treatment of alloys containing the gold group metals either alone or associated with osmium and ruthenium is discussed.

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Zusammenfassung Die vorliegende Arbeit beschäftigt sich mit der Mikroanalyse der Goldgruppe vonA. A. Noyes undW. C. Bray. Das gegebene Trennungsverfahren sieht Abscheidung, Mengenschätzung und Nachweis von 10 eines jeden Gliedes der Gruppe in der Gegenwart der zehnfachen Menge eines beliebigen anderen Gliedes der Gruppe vor. Die Äthylazetatextraktion des Makroverfahrens wurde nur in Abwesenheit von Quecksilber für die Isolierung des Goldes beibehalten. In Gegenwart von Quecksilber wurde vorgezogen, das Gold mit Natriumnitrit zu fällen und das Quecksilber aus dem Filtrat mitReinecke-Salz auszuscheiden. Das Verfahren vonGilchrist undWichers wurde zur Trennung des Platins von Palladium, Rhodium und Iridium durch hydrolytische Fällung der wasserhaltigen Oxyde der drei letztgenannten Metalle herangezogen. Die Trennung des Rhodiums vom Iridium wurde entweder durch Fällung mit Kaliumnitrit oder durch Fällung mit Kaliumäthylxanthogenat herbeigeführt.Für den Nachweis von Palladium, Rhodium und Iridium wurden neue Verfahren ausgearbeitet, die in getrennten Abhandlungen genauer besprochen werden. Im Anhang dieser Arbeit wird die Behandlung von Legierungen besprochen, welche die Metalle der Goldgruppe entweder allein oder in Begleitung von Osmium und Ruthenium enthalten.

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Abstract from a thesis submitted to the faculty of the Graduate School of the University of California, Los Angeles, in partial fulfillment of the requirements for the degree of Doctor of Philosophy.

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With 7 figures.     

Mass-spectrometric analysis of the products formed in a D.C. Arc Plasma

Summary The carbon content was determined in the plasma of horizontal electric arc discharging between carbon electrodes in a) a graphite tube and b) a ceramic tube, in the presence of an inhomogeneous magnetic field. After 20 s of discharge, the carbon content reaches in the case a) a value of 8% and in the case b) a value of 3%. The compositions of the air plasma with 8% and 3% of carbon, respectively, in the temperature range of 500–6000 K were calculated according to the method described by White [8, 9] and the results obtained were compared with the experimental data. Carbon is present below 5000 K mainly in the form of CO and CO₂.

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Massenspektrometrische Analyse der im Gleichstrombogen-Plasma gebildeten Produkte

Zusammenfassung Der Kohlenstoffgehalt im Plasma einer horizontalen Bogenentladung zwischen Kohleelektroden im inhomogenen Magnetfeld wurde in einem Graphitrohr (a) und in einem Keramikrohr (b) gemessen. Nach 20 s Entladungsdauer erreichte der Kohlenstoffgehalt bei a) einen Wert von 8%, und bei b) von 3%. Die Zusammensetzung des Luftplasmas mit 8% bzw. 3% C wurde für den Temperaturbereich 500–6000 K nach White [8, 9] berechnet und mit den experimentellen Ergebnissen verglichen. Unter 5000 K liegt Kohlenstoff hauptsächlich als CO und CO₂ vor.

     

Theoretical analysis of the influence of the adsorption process on the voltammetric curves in the case of a second order adsorption step followed by a first order charge transfer reaction: Part III. Variation of the transfer coefficient and application to semiconductor electrodes in l.p.s.v. and s.s.c.v.

The kinetic behaviour of a two-step sequential reaction including a 2nd order adsorption process is treated theoretically in the case of semiconductor electrodes. It is shown that the electronic structure of the semiconductor can be taken into account in some simplified cases by introducing a formal transfer coefficient comprised between 0 and 1 and potential independent. In both linear potential sweep voltammetry and steady state cyclic voltammetry, the usual characteristic features (E_M, _M, i_M) of the voltammetric curves are calculated as a function of the sweep rate for different values of the transfer coefficient.     

Studies of the cathode layer of a d.c. arc

Some factors which affect the cathode layer of a d.c. arc were investigated. It is shown that: (i) varying concentrations of elements with low ionisation potentials in the sample can markedly affect the distribution of atoms in the cathode layer and hence the detection limits of the technique; (ii) variations in arc current and arc gap have only a small effect on the cathode layer provided that these factors are maintained at values above certain minimum levels; (iii) the use of artifical atmospheres and inhomogeneous magnetic fields generally increase detection limits; (iv) detection limits obtained with samples containing relatively high concentrations of elements with low ionisation potentials can be two or three times better than those obtained with conventional anode evaporation techniques provided wandering of the cathode spot is kept to a minimum, a condition which often cannot be realised in practice.     

Formation of a carboxyl group satellite line in the n.m.r. spectra of solid carboxylic acids

The structural factors resulting in the formation of the carboxyl group satellite line on the low field side of the ¹H n.m.r. spectra of carboxylic acids in the solid state have been determined from the temperature dependences of the carboxyl proton chemical shifts of acetic, dimethylacetic, ethylacetic, phenylacetic, benzoic, o-methylbenzoic, p-methylbenzoic and adamantyl carboxylic acids. The carboxyl group low field satellite forms at temperatures near the melting point only in the case of carboxylic acids with bulky hydrocarbon radicals (o-methylbenzoic and adamantyl carboxylic acids).     

Cationic copolymerization of tetrahydrofuran with epoxides. I. Polymerization mechanism in the presence of a glycol

Polymerization of several epoxides and their copolymerization with tetrahydrofuran have been studied. The polymerizations were carried out by use of BF₃·O(C₂H₅)₂ as catalyst in the presence of 1,4-butanediol. Variations of catalyst and 1,4-butanediol ratio and concentration affect polymerization rate, molecular weight, and the formation of cyclic oligomers. The latter is also influenced by monomer fed ratio in the case of the copolymerizations. These effects are discussed, and some observations are made concerning the mechanism, particularly with respect to the role of the 1,4-butanediol. Mayo-Lewis monomer reactivity ratios were determined. The ratios found differed from previously published figures.     

Effect of a d.c. electric field on the fluorescence spectra of cationic polymethine dyes in a polymer film

We have observed that in an external d.c. electric field, in the differential fluorescence spectra of both symmetric and asymmetric polymethine dyes in a polymer film, the intensity of the emission in the long-wavelength region of the band increases while the intensity in the short-wavelength region decreases. In symmetric polymethines, these effects are opposite to those in the differential absorption spectra, while in asymmetric polymethines they are symbatic. The spectral effects were interpreted by a change in the probability of the vibronic transitions due to redistribution of electron density in the chromophore, in the ground state and the excited state of the dye, in an external electric field. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 6, pp. 343–347, November–December, 2008.     

Effect of CsCl-graphite buffer on the properties of a d.c. arc in the emission-spectrometric analysis of neodymium oxide

Summary The effects of CsCl-graphite buffer on the properties of a d.c. arc in the emission-spectrometric determination of traces of rare earth elements in neodymium oxide were investigated by measuring the line intensity, arc temperature, electron density, atomic concentration and residence time of rare earth particles in the arc plasma. The buffer gives a constant rate of evaporation of rare earth elements, as well as greater volatility of the sample and causes the increase of the number of atoms in the arc plasma. The atoms and ions of rare earths distribute uniformly along the axis of the discharge gap. This enhancing effects are interpreted by the decrease of the ionization degree of rare earths with increasing electron density, and by the increase of the residence time of the atoms and ions of rare earths in the arc plasma. The buffer enhances the sensitivity and reproducibility and permits the determination of microquantities of rare earth elements with limits of detection from 2 to 9 ppm in neodymium oxide. The coefficients of variation are less than 14%.

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Beeinflussung der Eigenschaften eines Gleichstrombogens bei der emissionsspektrometrischen Analyse von Neodymoxid durch einen CsCl-Graphit-Puffer

Zusammenfassung Die Wirkung des Puffers wurde durch Messung der Linienintensität, der Bogentemperatur, der Elektronendichte, der Atomkonzentration und der Verweilzeit der Teilchen im Bogenplasma untersucht. Durch den Puffer wird eine konstante Verdampfungsgeschwindigkeit der Seltenen Erden, eine größere Flüchtigkeit der Probe, eine Erhöhung der Anzahl der Atome im Bogenplasma und eine gleichmäßige Verteilung der Atome und Ionen der Seltenen Erden längs der Bogenachse erzielt. Diese Wirkungen werden durch die Abnahme des Ionisierungsgrades der Seltenen Erden mit steigender Elektronendichte und der Zunahme der Verweilzeit der Atome und Ionen im Bogenplasma erklärt. Der Puffer verbessert die Empfindlichkeit und Reproduzierbarkeit und gestattet die Bestimmung von Mikromengen Seltener Erden in Neodymoxid mit Nachweisgrenzen von 2–9 ppm. Die Variationskoeffizienten liegen unter 14%.

     

CO oxidation over the Pt-Rh system. 3. Reaction on a heterophase surface

The reaction of the CO oxidation over a Pt-Rh heterophase surface, which represents 10-20 nm platinum particles located on a rhodium film, which in turn is deposited on an inert support, has been investigated at low pressures (P < 2'10^-5 mbar). The results are compared with the data for the clean surfaces of Pt and Rh. In the high-temperature range, the rate of CO₂ formation on the heterophase surface is found to be higher than the sum of the rates on individual metals corrected by the surface area of the different metals. The nature of the synergistic effect in the CO oxidation is discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis of new heterocycles of the benzo[a] quinolizine group V. Synthesis of the 1-methylhexahydrobenzo[a] quinolizin-2-ones. Preparation of the cis-junction isomer

The reaction of 3,4-dihydro-6,7-dimethoxyisoquinoline hydrochloride on ethyl vinyl ketone yields two cis and trans benzo[a quinolizinone isomers in variable proportions depending on the pH of the reacting medium. The cis junction isomer can be stabilized and isolated as the β-propionylethylquinolizinium chloride quaternary salt.     

Polarization energy of a localized charge in a molecular crystal. VI. Effect of excitons

The polarization energy of a localized charge carrier in a molecular crystal changes by ΔP near an exciton, viewed as a localized excited molecule of changed polarizability. Experimental polarizability changes in the first excited singlet state are used to calculate ΔP for various carrier and exciton positions in benzene, naphthalene, anthracene and tetracene. As the excited-state polarizability is larger, ΔP is normally negative, with minima ranging from ?12 meV in benzene to ?83 meV in tetracene. The change in charge-quadrupole energy ΔW_Q is estimated for naphthalene using a theoretical quadrupole moment for the first triplet state. At most sites |ΔW_Q| > |ΔP|, but the sign of ΔW_Q varies. The net exciton interaction with electrons in naphthalene varies from ?49 to +45 meV and with holes from ?106 to +29 meV. This behaviour is broadly complementary to that previously calculated for vacancies.     

Phytoecdysteroids of plants of the genusRhaponticum I. Carthamosterone a fromRh. carthamoides

A new ecdysteroid — carthamosterone A — has been isolated from the seeds ofRhaponticum carthamoides. Its structure has been established from the results of spectral investigations.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 40 64 75. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 392–394, May–June, 1997.     

Spectrographic a.c. spark method for the estimation of yttrium in rare earth mixtures

Summary The spectrographic estimation of yttrium in rare earth mixtures was achieved within a concentration range of 1–90% by means of the a.c. spark method using a large quartz spectrograph. The sample was mixed with ceria and zinc oxide in the ratio 212. The Y lines 2414.68 Å and 2856.36 Å were used as analytical lines for the ranges of 1–15% and 10–90%, respectively. The Ce line at 2603.65 Å served as internal standard line. The standard deviation was 2–5%.

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Spektrographische Bestimmung von Yttrium in Gemischen Seltener Erden mit Hilfe der Wechselstrom-Funken-methode

Zusammenfassung Yttrium konnte im Konzentrationsbereich von 1–90% mit einem großen Quarzspektrographen bestimmt werden. Die Probe wird mit Cerdioxid und Zinkoxid im Verhältnis 212 gemischt. Als Analysenlinie dient die Y-Linie 2414,68 Å (1–15%) bzw. 2856,36 Å (10–90%). Als innere Standardlinie wird die Ce-Linie 2603,65 Å verwendet. Die Standardabweichung betrug 2–5%.

     

Investigations on electric properties of polymers—V: On the a.c. conductivity of polyphenylacetylenes

The electric conductivity of polyphenylacetylene with various physical and isomeric structures (cis-cisoidal, cis-transoidal and trans-cisoidal) was investigated over the frequency and temperature ranges of 10-10⁵ Hz and 273–347 K, respectively. The transient currents from polyphenylacetylene having cis-cisoidal structure were also studied at 293 K. It was found that a.c. conductivity of cis-cisoidal polymer can be explained in terms of a hopping mechanism. The type of mechanism (classical or quantum) depends both on frequency and temperature. At temperatures <284 K and high frequencies, the quantum mechanism (predominantly by single hops) is involved. As frequency decreases and temperature increases, there is a gradual passing to the classical mechanism (many multiple hops) and then to the Maxwell-Wagner conduction. The electric properties of cis-transoidal polymer are similar to those of trans-cisoidal one, but are different from those for the cis-cisoidal structure. The quantum hopping mechanism, almost entirely involving single hops, seems to predominate in these two polymers. Adsorption of oxygen decreases both conductivity and dielectric constant, as compared with those in nitrogen, only in the case of cis-cisoidal polymer.     

Studies on the synthesis of heterocyclic compounds. XV. Preparation of a new series of macrocycles with the diglycolyl moiety

A new series of macrocycles containing the diglycolyl moiety have been prepared. The compounds prepared were: 7,9,18,20-tetrahydrodibenzo[b,k][1,4,7,10,13,16]hexaoxacyclooctadecin-6,10,17,21-tetraone ( 1 ), 1,4,7,10,13,16-hexaoxacyclooctadecane-2,6,11,15-tetraone ( 2 ), 8,7,17,18-tetramethyl-1,4,7,10,13,16-hexaoxa-cyclooctadecane-2,6,11,15-tetraone ( 3 ) and 2,5,8,15,18,21 -hexaoxatricyclo[20,4,0,0^9.14]hexacosan-3,7,16,20-tetraone ( 4 ). The compound 4 has been isolated in the four diastereoisomers: trans-syn-trans 4a , trans-anti-trans 4b , cis-syn-cis 4c and cis-anti-cis 4d .