Determination of oxygen-18 in inorganic compounds

A relatively simple and rapid method has been developed for the analysis of the oxygen-18 content of many inorganic compounds including water. The samples are heated with silver cyanide at 500 degrees and the carbon dioxide formed is separated from the other products by means of a methylcyclohexane slush at -130 degrees and analysed mass spectrometrically.     

A gaschromatography apparatus for the investigation and separation of radioactively labelled inorganic compounds at high temperatures

Summary A gas chromatography apparatus for experiments with radioactively labelled compounds which enables temperatures up to 1100 K and corrosive carrier gases to be used is presented. Possible applications are discussed and results from several investigations are presented. The main applications are to non-analytical gas chromatography (determination of adsorption or absorption data) and the development of separation methods for analytical or preparative inorganic gas chromatography.

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Zusammenfassung Ein Gaschromatograph wurde beschrieben, mit dessen Hilfe Trennungen radioaktiv markierter anorganischer Verbindungen bis zu Temperaturen von 1100 K in Anwesenheit korrosiver Trägergase durchführbar sind. Mögliche Anwendungen wurden diskutiert und Beispiele für Ergebnisse von Trennungen angegeben. Die Hauptanwendung ist die nichtanalytische Gaschromatographie (Bestimmung von Adsorptions- oder Absorptionsdaten) und die Entwicklung von Trennmethoden für analytische oder präparative anorganische Gaschromatographie.

     

Deuterium labelled liquid crystalline compounds

Abstract

The synthesis of 4-(2′-methylbutyl)phenyl4′n-heptylbiphenyl-4-carboxylate-d ₁₈(7BEF5-d ₁₈) is presented. The compound is intended to be used as a means of studying the collective modes of liquid crystals by the coherent inelastic neutron scattering technique. The 4′-n-heptylbiphenyl-4-carboxylic acid-d ₁₂, a liquid crystalline intermediate was prepared as well; its acid chloride was coupled with 4-(2′-methylbutyl)phenol-d ₆ to obtain the final product. The intermediates and final products were investigated by spectroscopic methods.     

Preparation of inorganic crystalline compounds induced by ionizing,UV and laser radiations

Results on preparation of nickel, zinc, yttrium, aluminum and cobalt oxides, zinc peroxide and hydroxide, yttrium and lutetium aluminum garnets and cobalt(II) aluminate via irradiation of aqueous solutions containing soluble metal salts and radical scavengers (formate anion or propan-2-ol) are summarized in this paper. Various physico-chemical and structural properties of prepared compounds (e.g. crystallinity, specific surface area, particle size) are also reported.All used variants of radiation method are rather convenient and simple, and yield nano-scale powder materials with interesting characteristics. Prepared materials generally have high chemical purity, high specific surface area and narrow distribution of particle size (ranging in tens of nm).Generally, accelerated electrons, gamma, and UV radiation yield materials with comparable properties and structural characteristics, but UV-radiation seems to be the most convenient for preparation of intricate compounds such as synthetic garnets and spinels, while ionizing radiation is better for preparation of compounds doped with foreign ions.Among discussed compounds, only zinc oxide, peroxide and hydroxide were prepared directly via irradiation. For preparation of other crystalline oxidic compounds, mild heat treatment of amorphous or weakly crystalline solid phase was necessary.     

Micellar chromatography of inorganic compounds

Micellar chromatography has been used to separate various compounds and to determine the partition coefficients of the compounds between aqueous bulk solution and a micellar pseudophase. The application of this method to inorganic analyses is less common than its application to organic analyses, albeit the former application gives fundamental aspects of the micellar partition of simple ions and promises developments of novel separation. In this review, we focus our attention on the fundamental aspects of micellar chromatography mostly in inorganic analysis of simple ions.     

Synthesis of C-11 and F-18 labelled compounds for biomedical applications: Current status and challenges for the future

The synthesis of¹¹C and¹⁸F labelled compounds for biomedical applications is a rapidly growing field with applications in Neurology, Cardiology, Oncology and the study of human biochemistry and physiology. Literally hundreds of compounds have been labelled but only a few have made their way into human studies with the bulk being used in animal studies. This review focuses on the production of these isotopes, the chemistry of labelling radiopharmaceuticals with these isotopes, automated chemistry and finally future considerations and applications for both¹¹C and¹⁸F.     

Enzymic preparation of dioxygen-18 labelled leukotriene E4 and its use in quantitative gas chromatography-mass spectrometry.

A simple and rapid method is described for the preparation of a stable isotope oxygen-18 labelled leukotriene E4 (LTE4). Oxygen-18 labelling of LTE4 methyl ester in oxygen-18 water catalysed by a pig liver esterase resulted in the incorporation of two oxygen-18 atoms in the carboxylic group of LTE4 to the extent of 89.8% ([18O2]LTE4) and one oxygen-18 atom to the extent of 9.4% ([16O18O]LTE4), with only 0.7% remaining unchanged ([16O2]LTE4). [18O2]LTE4 was found not to back-exchange following incubation in acidified urine (pH 4.0) at 4 degrees C for up to 20 h. [18O2]LTE4 was demonstrated to be a useful internal standard in a method for the quantitative determination of LTE4 in human urine involving high-performance liquid chromatography and gas chromatography with negative-ion chemical ionization tandem mass spectrometry: the concentration of LTE4 in a 24-h urine sample of a healthy subject was determined to be 68.1 pg/ml.     

Preparation and storage of125I labelled endothelin

Endothelin (ET) is a novel endothelium-derived vasoconstrictive peptide, purified from porcine aortic endothelial cells.¹²⁵I-ET was prepared by lodogen method and purified by HPLC, the specific activity was 62.9 TBq/mmol. The stability of¹²⁵I-ET was investigated in different storage conditions by radioimmunoassay.     

Novel use of an isotope separator to determine the position of fluorine-18 in labelled 1,1,1,2-tetrafluoroethanes

A novel technique is described for measuring the site selectivity of methods for labelling the major CFC-alternative, 1,1,1,2-tetrafluoroethane (HFA 134a), with fluorine-18 (t_1/2 = 109.7 min). The carbon–carbon bond in radiofluorinated HFA 134a is broken in the ion source of an isotope separator. Radioactivity associated with the ion beam of the [CF₂ ¹⁸F]^+. fragment (m/z = 68) is collected, measured and divided by the integrated mass of the simultaneously collected ion beam for the [CF₃]^+. fragment (m/z = 69) to give the ‘specific radioactivity’ (in nCi nmol^–1) of the radiolabel in the 1-position. Similarly, the ‘specific radioactivity’ of the radiolabel in the 2-position is calculated from the measured radioactivity of the ion beam from the [CH₂ ¹⁸F]^+. fragment (m/z = 32) and the integrated mass of the simultaneously collected ion beam from the [CH₂F]^+. fragment (m/z = 33). The selectivity of the labelling procedure for a particular position is then given by the decay-corrected ratio of specific radioactivity at that position to the sum of specific radioactivities. The labelling of HFA 134a by the reaction of [¹⁸F] fluoride with trifluoroethylene was found to have 97% selectivity for the CF₃ group, whereas labelling by the reaction of [¹⁸F] fluoride with 2,2,2-trifluoroethyl p-toluenesulphonate was found to have 91% selectivity for the CH₂F group. This information is of value for tracer studies of the fate of HFA 134a in man following its inhalation as a drug propellant. The described technique is of potentially wider value for determining the position of fluorine-18 in labelled polyfluorinated molecules.     

Gas chromatography of inorganic radioactive compounds

An experimental arrangement for the separation of inorganic radioactive compounds is given using gas chromatography. Volatile chlorides are separated either in quartz tubes or in tubes which are coated with alkali chlorides. The separations are carried out either isothermal or with a temperature program. The results are discussed as a function of the different parameters.     

Preparation of 35-sulphur labelled sulphur tetrafluoride

The synthesis of ³⁵S-labelled sulphur tetrafluoride from ³⁵S- labelled elemental sulphur and iodine pentafluoride is reported.     

Gas chromatographic separation of some labelled aromatic halogen compounds

Gas—liquid-chromatographic techniques for the separation of a large variety of mono-, di-and polysubstituted benzene derivatives from their multicomponent systems have been developed for the study of reactions of recoil halogen atoms with aromatic compounds. The¹⁸F,^34mCl,³⁸Cl,⁸²Br and¹²⁸I labelled benzene derivatives were produced by neutron irradiations of the corresponding liquid mixtures. Because of the short half-life of most of the isotopes in question a relatively fast method was required, therefore each of the techniques described takes less than one hour to achieve the separation.     

Structure-related melting and boiling points of inorganic compounds

The paper is aimed at rationalizing relationships between the structure of inorganic compounds in condensed phases and their melting and boiling points. It is documented that the main factor governing both points is their molecular or polymeric nature. In case of polymeric ionic compounds, the higher actual charge bearing by the ions involved, the higher their melting/boiling points. In case of covalent polymers, the value of both points increases with polymer dimensionality (1D → 2D → 3D polymers) and with the number and energy of the respective covalent bonds. In case of molecular compounds, both points depend on the weight and shape of molecules, the presence of hydrogen bonds, and electric quadrupole moment.     

Preparation of high purity labelled Rose-Bengal with radioiodine

The exchange of Rose-Bengal in the mono-sodium salt with elementary¹³¹I in an organic medium allows for the preparation of a labelled product substantially higher in radiochemical purity than that produced by other methods. Purification of the starting material before the labelling process has been done by adsorption chromatography. Under the conditions described a radiochemical yield more than 97% can be obtained within 30–60 minutes. The product was stable during sterilization and storage for 10 days and was found to be free of¹³¹I.     

Preparation of polymer resin and inorganic oxide supported peroxy-acids and their use in the oxidation of tetrahydrothiophene

Peroxy-benzoic acid residues have been attached to polystyrene resins with nominal crosslink ratios of 5–40%, and also to various commercially available silicas and aluminas. Chemical modification of the resins becomes increasingly difficult as the crosslink ratio is increased, although resistance to oxidative degradation by hydrogen peroxide in methanesulphonic acid is simultaneously enhanced. Two different linkages were employed for the binding of peroxy-acid groups to the inorganic oxide supports, one involving a direct silicon aromatic bond and the other with an ethylene bridge interposed. In both cases, the introduction of peroxy-acid groups proceeded with ease and without any apparent degradation although the loadings achieved were somewhat lower than with the resins, as anticipated. All the supported peroxyacids functioned as oxidants for tetrahydrothiophene, the 5% crosslinked species being the most effective of the resin bound acids. One macroreticular resin displayed partial selectivity in oxidizing the thioether to its sulphoxide rather than sulphone. The best of the inorganic oxide supported oxidants approached closely to the reactivity shown by the 5% crosslinked resin; a mixed silica/alumina support showed the highest selectivity for sulphoxide formation in the case when its bound peroxy-acid was attached by a direct silicon aromatic bond.     

Structure maps of ABX4 inorganic compounds

Data on the structure types of ABX₄ compounds have been systematized in the form of structure maps. The major factor of the efficiency of crystal-chemical systematization is the inclusion of ionic potentials. The maps constructed with the use of the generalized force parameter K _AB turned out to be most adequate from the viewpoint of arrangement of size, energetic, and force characteristics of structures and separation of coordination fields.     

Analysis of inorganic compounds by paper chromatography

A Chromatographic method for the separation and detection of lead, silver, and mercury by extraction with organic solvent mixture on strips or sheets of filter paper, is described. Study of various physico-chemical factors responsible for the separation of cations has been made.

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Zusammenfassung Es wird eine chromatische Methode zur Trennung und Feststellung von Blei, Silber und Quecksilber durch Extraktion mittels Gemischen aus organischen Flüssigkeiten auf Papierstreifen beschrieben und die verschiedenen für die Trennwirkung verantwortlichen physikalisch-chemischen Faktoren werden betrachtet.

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The thanks 01 the author are due to Dr. N. Ghatak, D. So., Chemical-Examiner to the Government of Uttar Pradesh, for his keen interest in this investigation.